COMMUNITY MEIDCINE NOTES
Z-tests and t tests
Data types that can be analysed with z-tests

data points should be independent from each other

z-test is preferable when n is greater than 30.

the distributions should be normal if n is low, if however n>30 the distribution of the data does not have to be normal

the variances of the samples should be the same (F-test)

all individuals must be selected at random from the population

all individuals must have equal chance of being selected

sample sizes should be as equal as possible but some differences are allowed

Data types that can be analysed with t-tests

data sets should be independent from each other except in the case of the paired-sample t-test

where n<30 the t-tests should be used

the distributions should be normal for the equal and unequal variance t-test (K-S test or Shapiro-Wilke)

the variances of the samples should be the same (F-test) for the equal variance t-test

all individuals must be selected at random from the population

all individuals must have equal chance of being selected

sample sizes should be as equal as possible but some differences are allowed

Limitations of the tests

if you do not find a significant difference in your data, you cannot say that the samples are the same

Introduction to the z and t-tests

Z-test and t-test are basically the same; they compare between two means to suggest whether both samples come from the same population. There are however variations on the theme for the t-test. If you have a sample and wish to compare it with a known mean (e.g. national average) the single sample t-test is available. If both of your samples are not independent of each other and have some factor in common, i.e. geographical location or before/after treatment, the paired sample t-test can be applied. There are also two variations on the two sample t-test, the first uses samples that do not have equal variances and the second uses samples whose variances are equal.

It is well publicised that female students are currently doing better then male students! It could be speculated that this is due to brain size differences? To assess differences between a set of male students' brains and female students' brains a z or t-test could be used. This is an important issue (as I'm sure you'll realise lads) and we should use substantial numbers of measurements. Several universities and colleges are visited and a set of male brain volumes and a set of female brain volumes are gathered (I leave it to your imagination how the brain sizes are obtained!).

Hypotheses

Data arrangement

Excel can apply the z or t-tests to data arranged in rows or in columns, but the statistical packages nearly always use columns and are required side by side.

Results and interpretation

Degrees of freedom:

For the z-test degrees of freedom are not required since z-scores of 1.96 and 2.58 are used for 5% and 1% respectively.

For unequal and equal variance t-tests = (n1 + n2) - 2

For paired sample t-test = number of pairs - 1

THE FIRST HEAD TRANSPLANT (stranger than fiction)

Head Transplant

In the 1950s, at the height of the cold war, Stalin turned his attention to medicine as a way to advance technology and put the USSR ahead of the west.

To this end, just outside Moscow, Stalin established secret medical laboratories to explore and develop new concepts. Scientists were encourage to experiment freely in the search for the secrets to prolonging life. Many of these tests were carried out on animals. Organs were removed from the corpses and kept alive with machines. Dogs were put to death and subsequently brought back to life.

Vladimir Demikhov, a veteran of the Red Army hospitals in World War 2, believed it was possible to transplant organs like the heart and lungs in human beings. Even in the science-mad 50s this sounded far-fetched.
Vladimir Demikhov
Vladimir Demikhov

However, Demikhov proved it could be done, by transplanting the heart and lungs from one dog to another. His experiments laid the ground-work for future medical success in humans, but his work never received the recognition it deserved. Demikhov was preparing plans for a human heart transplant, 16 years before the first one was actually achieved.

One night in 1954, Demikhov undertook an experiment that stunned the world. He took two dogs, one fully grown, the other a puppy. He, and his team of surgeons, operated on them through the night. The following morning Demikhov unveiled his achievement. It was a creature straight out of science-fiction.


Two Headed Dog
A Very Blurry Two Headed Dog

He had stitched the head and upper-body of the puppy onto the neck of the larger dog, connecting their blood-vessels and windpipes. Soviet propaganda trumpeted his achievement. In America, this caught the attention of an ambitious young scientist: Robert White.

For an America in the grip of cold-war paranoia, the prospect of Russian two-headed dogs was too much to ignore. The United States would soon begin it's own head-transplant programme.

Robert White was born in Minnesota, in 1926. Like Demikhov, he was a veteran of World War 2. After the war, White attended Harvard Medical School, where he studied to be a brain surgeon.

In 1960, the US Government, eager to stay ahead of the Russians in all aspects of medical science, helped White establish a specialist laboratory at the County Hospital in Cleveland, Ohio. Here he set about creating a world-leading brain research centre.

By day, White operated on patients with all kinds of brain injuries and illnesses. His surgical skills were renowned. But, as a scientist, it was the mysteries of the brain he wanted to unlock. His ambition was to be the first person, in the world, to isolate the brain. To take it out of the skull, to study it, and to keep it alive throughout.

White was convinced it was possible to remove the brain from the skull and keep it alive. In 1962, he achieved a world's-first by successfully removing an animal's brain and keeping the brain alive. In 1964, he came up with a more audacious plan, to transplant the brain of one animal into the body of another and study it from there.


Transplanted Brain
How the Transplanted Brain was Located

He removed the brain of one dog and transplanted it into the neck of a second dog. The brain was connected to the blood supply of the host animal and electrodes were put in place to monitor the brain's activity. This begged the question: "If the brain is alive, is it conscious?" It was a question White could not answer.

White's work was not unnoticed in the Soviet Union, and, unusually, there followed a number of visits by the Russians to the Ohio facility and a number of reciprocal visits by White to Russia.

One person that White was keen to meet, was tha man who had inspired him years before - Vladimir Demikhov. Demikhov had continued his work with organ transplants and had revolutionised heart surgery. However, by 1966 he had fallen foul of the authorities, who thought his methods outlandish.

Following his visits to Russia, White returned with ideas to prove a transplanted brains consciousness. He had learned of experiments carried out by the Soviets where the severed head of a dog was kept alive and displayed cognitive reactions.

Robert White decided that if he could transplant a head from one monkey to another, then it would be apparent of the brain activity represented awareness. It took him three years to plan the surgery. He knew that this would be, to some, morally offensive.

In order to keep the head alive the the blood-flow from monkey B's body had to be transfused to monkey A's head via a network of plastic tubes. The A head was brought onto the B body and the blood vessels were connected together, but the spinal cord was left, it's impossible to reconnect nerve threads once they are broken.


Monkey Heads
Connecting the Head

When the surgery was complete and the monkey came out of the anaesthetic it could move it's facial muscles, it could be fed and follow movements with it's eyes. Of course, with a severed spinal cord it was paralysed from the neck down, but the operation had been a success.

Child's sex is determined by mother's diet during pregnancy and before

Dr Fiona Mathews said: "Potentially, males of most species can father more offspring than females, but this can be strongly influenced by the size or social status of the male, with poor quality males failing to breed at all. Females, on the other hand, reproduce more consistently. If a mother has plentiful resources then it can make sense to invest in producing a son because he is likely to produce more grandchildren than would a daughter. However, in leaner times having a daughter is a safer bet."

Although sex is genetically determined by fathers, mothers therefore appear able to favour the development of one sex of infant rather than another. The mechanism is not yet understood in mammals, but it is known from IVF research that high levels of glucose encourage the growth and development of male embryos while inhibiting female embryos. In humans, skipping breakfast depresses glucose levels and so may be interpreted by the body as indicating poor environmental conditions and low food availability.

The group of women taking part in the study was representative of the UK average in terms of the weight, health and lifestyle. The findings showed no evidence of a link between a mother smoking and drinking caffeine prior to pregnancy and the gender of her baby. There was also no correlation between the body mass index (BMI) of a mother and the sex of her child. Although this research provides the first link between a human mother's diet and the sex of her offspring, there is still no evidence that diet during pregnancy, rather than around the time of conception, plays any role in the sex of a fetus.

MY TRIP TO MANGALORE TO ATTEND INTERNATIONAL CONFERENCE

MANGALORE TRIP
May be it was not possible in our dream to meet and talk with “Dr. VINAY KUMAR “Celebrated author of ROBBIN’S PATHOLOGY , who was star attraction in the event “MEDICON 2009”.
THE PROGRAM WAS FROM 24TH JUNE TO 28TH JUNE .
Before starting our trip,I would like to thank Dr. Ravi Shankar and Department of community medicine :-AMITA MAM , SRIJANA MAM without whose sincere support the way to our conference would not have paved.
We started our journey on thrusday (18th JUNE ) 8:30 PM for bhairahwa.Next morning on Friday we reached ,stayed there for a single day and and on the same evening we went to Gorakhpur .Saturday(20TH JUNE) morning ,6:30 am we started our train journey .On one side heart full of joy ,plans(some of them were success and some are still plans). And on the other side missing college, home and some one ………...After 48 hrs long journey, on Monday ,we reached BANGALORE. The same evening we moved for Mangalore in train .it was 9:30 am ,Tuesday when we reached Mangalore(the home town of MEDICON 2009).There we were shifted to respective apartment.
The inauguration of MEDICON 2009 “THE SECOND ASIAN AND THIRD NATIONAL CONFERENCE “ organized by MANIPAL UNIVERSITY’S Kasturba medical college at DR.TMA PAI INTERNATIONAL CONVENTION CENTRE ,MANGALORE Started with the message “CATCH ‘EM YOUNG”.
Dr.Katoch, Secretary Of Union Health Research Department and Director Of ICMR(INDIAN COUNCIL OF MEDICAL RESEARCH ) was our chief guest who inaugurated the program calling upon the students to develop an instinct to think rather than study .”we have knowledge and potential, we have to create the pathway to provide opportunity “,he said. VICE CHANCELLOR OF MANIPAL UNIVERSITY “Dr.Raj warrior “ said that research projects worth Rs.30 crore are already underway at MANIPAL UNIVERSITY which produced 1,300 research papers in the previous year.
More than 800 delegates ,including from Pakistan ,iran ,Romania and Nepal and many more took part in the conference.
Most memorable moments of our trip :-
· GOT CHANCE TO SEE LIVE RARE AUTOPSY IN KASTURBA MEDICAL COLLEGE.(thanks to Dr.Ritesh Menezes)
· AUTOGRAPH AND PHOTOGRAPH FROM Dr.VINAY KUMAR .
· PANAMBURA SEA BEACH.
· GADBAD ICE-CREAM IN PABBAS ICE-CREAM PARLOUR .
· “BHARAT MAHAL” A HUGE COMPLEX ..(ACTUALLY IT WAS OUR JUNCTION )
· St.ALOYSUS CHURCH ,125 YEARS OLD ,THE WHOLE CHURCH CRAVED BY A SINGLE PERSON IN 2 YEARS .
· MEETING WITH DIFFERENT INDIAN ENTITIES AND MEDICAL IDOLS FROM ALL OVER THE WORLD.
· MEETING WITH INTERNATIONAL DELEGATES .
· VISIT TO MANIPAL “REALLY ,FEELS LIKE IN HEAVEN .”ACTUALLY IT WAS MY DREAM .....
· WELCOME PARTY BY MANIPAL STUDENTS.

The last day trip to MANIPAL UNIVERSITY was most memorable.playing antarakshi with the foreign and DUMB SHAKE was really joyful and on top of that interaction with people.AND THE MANIPAL UNIVERSITY ,ITS HUGE LIBRARY ,TOP ANATOMY MUSEUM ,LARGEST PARK ,AND MANY MORE…..
I really wanna thank research team “krabs” especially roshan ,shamini,pragya,………………..,who helped till the last moment ,with out whom I would not have attended the conference.I returned back with lots of photographs, videos ,and memories of manipal and medicon which will remain with me forever as a gift ,my college provided me in my medical life.
Thanks to all the supporters and well wishers….

MY SCHOOL FRIENDS


JUNU DAHAL
AASTHA KHATIWADA
SHRADHA PRADHAN
ANUGYA AMATYA
ROJU BASNET
RICHA SHRESTHA
RINKU NIRAULA
DIVYA KABRA
PAYAL ATAL
BABY GOYAL
BOBBY LODHA
AYUSHI AGRAWAL
GUNJA SINGH
JYOTI KHETANG
JANAK DAHAL
DEEPAK YADAV
MANISH BHAGAT
JAY PRAKASH SONI
JAY PRAKASH SHAH
BIVEK SINGH
RUJJUWAL SHARMA
BIKAL GAUTAM
DHIRAJ POKHEREL
SUDEEP WOSTI
SITAL TRIKHATRI
PRATEEK DHAKAL
PRATIK KOIRALA
OJESH DUGAR
SUMEET PAREEK
ASHISH SARDA
PRADEEP CHAUDHARY
SAMEER KARKI
RAJEEV TIWARI
PLEASE INFORM ME ABOUT OTHER NAMES
callmyfrens_121@yahoo.com

WHY I JOINED KIST MEDICAL COLLEGE..............