Even though a major German encyclopedia (the 19th edition of the Brockhaus Encyclopedia, 1992) indicates that the word "Plastination" is derived from the Greek (from plassein = to shape, to form), the term is, in fact, a creation of Gunther von Hagens. He coined the term because "plastification" already had a fixed meaning in the field of polymer chemistry, and the expression used in the original patents of 1977/78 ("Polymer Impregnation of Perishable, Biological Specimens”) was not terribly catchy and was utterly inadequate for popularizing the new technology, particularly abroad. The following will provide an explanation of how Plastination works. We will first present the process in a general, comprehensible manner; for those with an interest, we will then go into more detail regarding the chemicals and chemical processes used.
A process at the interface of the medical discipline of anatomy and modern polymer chemistry, Plastination makes it possible to preserve individual tissues and organs that have been removed from the body of the deceased as well as the entire body itself. Like most inventions, Plastination is simple in theory: in order to make a specimen permanent, decomposition must be halted. Decomposition is a natural process triggered initially by cell enzymes released after death and later completed when the body is colonized by putrefaction bacteria and other microorganisms. By removing water and fats from the tissue and replacing these with polymers, the Plastination process deprives bacteria of what they need to survive. Bodily fluids cannot, however, be replaced directly with polymers, because the two are chemically incompatible. Gunther von Hagens found a way around this problem: In the initial fluidexchange step, water in the tissues (which comprises approximately 70% of the human body) and fatty tissues are replaced with acetone, a solvent that readily evaporates. In the second step, the acetone is replaced with a polymer solution. The trick that first proved to be critical for pulling the liquid polymer into each and every cell is what he calls "forced vacuum impregnation." A specimen is placed in a vacuum chamber and the pressure is reduced to the point where the solvent boils. The acetone is suctioned out of the tissue at the moment it vaporizes, and the resulting vacuum in the specimen causes the polymer solution to permeate the tissue This exchange process is allowed to continue until all of the tissue has been completely saturated—while a matter of only a few days for thin slices, this step can take weeks for whole bodies.
The second trick is selecting the right polymer. For this purpose, "reactive polymers" are used, i.e., polymers that cure (polymerize) under specific conditions, such as the presence of light, heat, or certain gases. Their viscosity must be low, i.e., they have to be very thin liquids; they must be able to resist yellowing; and, of course, they must be compatible with human tissue. The polymer selected determines the look and feel of the finished specimen.
Tuesday, 18 July 2017
Friday, 14 July 2017
How to conceive a boy
What’s a fact and what’s a fallacy?
Can’t I choose which sex my baby is?
|Characteristics of boy sperm||What this means to you|
|Are identified as looking like a Y||Nothing really, just an interesting point.|
|Are not as resilient or strong as girl sperm.||Interesting but nothing more.|
|Have short bursts of power before they fizzle out in energy.||This affects the timing of sex to coincide with ovulation; don’t expect them to hang around.|
|Are not capable of fertilising the egg past 24 hours after they have left the man’s body.||Timing sex to coincide with the day of ovulation may help slightly to increase the odds of having a boy.|
|Move at high speed towards the egg.||Interesting but out of your control.|
|Characteristics of girl sperm||What this means to you|
|Are identified as looking like an X.||Interesting – some people remember the differences because they claim that the extra arm on the x indicates more strength.|
|Are more resilient and live for longer than Y sperm. This means they can still fertilise the egg 4-5 days after they have left the man’s body.||You don’t need to be so particular about timing sex to coincide with ovulation. Female sperm can wait around for longer until the egg is ready to be fertilised.|
|Require less ‘nurturing’ to find their way to the egg.||Interesting, but you don’t need to do anything consciously to look after them. Just don’t douche.|
|Move more slowly than Y sperm but retain their energy.||Again, you don’t need to do anything in particular.|
Timing of intercourse
How do I know when I’ve ovulated?
General tips to help conceive a boy
What about the food I’m eating?
A pregnancy test may let you know, one way or the other, if you are pregnant.
Here are answers to some of the most common questions about pregnancy tests.
What is a pregnancy test and how does it work?
Pregnancy tests are designed to tell if your urine or blood contains a hormone calledhuman chorionic gonadotropin (hCG). This hormone is produced right after a fertilized egg attaches to the wall of a woman's uterus.
This usually happens -- but not always -- about six days after fertilization. If you're pregnant, levels of hCG continue to rise rapidly, doubling every two to three days.
What types of pregnancy tests are available?
Two main types of pregnancy tests can let you know if you're pregnant: urine tests and blood tests.
Urine tests can be done at home or in a doctor's office. Many women first choose a home pregnancy test to take about a week after a missed period. Home pregnancy testsare private and convenient.
These products come with instructions. Follow them closely for the most accurate results. After testing, you can confirm results by seeing your doctor, who can perform even more sensitive pregnancy tests.
Blood tests are done at your doctor's office, but are used less often than urine tests. These tests can detect pregnancy earlier than a home pregnancy test, or about six to eight days after ovulation. But with these tests, it takes longer to get the results than with a home pregnancy test.
Two types of blood pregnancy tests are available:
A qualitative hCG test simply checks to see if hCG is present. It gives a "yes" or "no" answer to the question, "Are you pregnant?" Doctors often order these tests to confirm pregnancy as early as 10 days after a missed period. However, some of these tests can detect hCG much earlier.
A quantitative hCG test (beta hCG) measures the exact amount of hCG in your blood. It can find even very low levels of hCG. Because these pregnancy tests can measure the concentration of hCG, they may be helpful in tracking any problems during pregnancy. They may also (in combination with other tests) be used to rule out a tubal (ectopic) pregnancy or to monitor a woman after a miscarriage when hCG levels fall rapidly.
How accurate are pregnancy tests?
You should know that waiting at least a week after a missed period may give you the most accurate result. Results may also be more accurate if you do the test first thing in the morning, when your urine is more concentrated.
Urine home pregnancy tests are about 99% accurate. Blood tests are even more accurate than this.
How accurate a home pregnancy test is depends upon:
- How closely you follow instructions.
- When you ovulate in your cycle and how soon implantation occurs.
- How soon after pregnancy you take the test.
- The sensitivity of the pregnancy test
Home pregnancy tests are quick and easy to use. They are also very accurate if you carefully follow directions. These pregnancy tests all work in a similar way. You test the urine in one of these ways:
- Hold the test's stick in your urine stream.
- Collect urine in a cup and then dip the test's stick into it.
- Collect urine in a cup and use a dropper to put urine into another container.
With all of these techniques, you need to wait a few minutes before seeing the results. Results may show up as a line, a color, or a symbol such as a "+" or "-" sign. Digital tests produce the words "pregnant" or "not pregnant."
If you have any questions about the pregnancy test or the results, call your doctor or the telephone number listed with the home pregnancy test.
What do the pregnancy test results mean?
It's important to know what a positive or negative result means.
If you get a positive result, you are pregnant. This is true no matter how faint the line, color, or sign is. If you get a positive result, you may want to call your doctor to talk about what comes next.
In very rare cases, you can have a false-positive result. This means you're not pregnant but the test says you are. You could have a false-positive result if blood or protein is present in your urine. And certain drugs, such as tranquilizers, anti-convulsants, or hypnotics, may also cause false-positive results.
If you get a negative result, you are likely not pregnant. However, you may still be pregnant if:
Wednesday, 12 July 2017
Most people who have trichomoniasis do not have any symptoms.
What is trichomoniasis?
Trichomoniasis (or “trich”) is a very common sexually transmitted disease (STD). It is caused by infection with a protozoan parasite called Trichomonas vaginalis. Although symptoms of the disease vary, most people who have the parasite cannot tell they are infected.
How common is trichomoniasis?
Trichomoniasis is the most common curable STD. In the United States, an estimated 3.7 million people have the infection. However, only about 30% develop any symptoms of trichomoniasis. Infection is more common in women than in men. Older women are more likely than younger women to have been infected with trichomoniasis.
Two Trichomonas vaginalis parasites, magnified (seen under a microscope)
How do people get trichomoniasis?
The parasite passes from an infected person to an uninfected person during sex. In women, the most commonly infected part of the body is the lower genital tract (vulva, vagina, cervix, or urethra). In men, the most commonly infected body part is the inside of the penis (urethra). During sex, the parasite usually spreads from a penis to a vagina, or from a vagina to a penis. It can also spread from a vagina to another vagina. It is not common for the parasite to infect other body parts, like the hands, mouth, or anus. It is unclear why some people with the infection get symptoms while others do not. It probably depends on factors like a person’s age and overall health. Infected people without symptoms can still pass the infection on to others.
What are the signs and symptoms of trichomoniasis?
About 70% of infected people do not have any signs or symptoms. When trichomoniasis does cause symptoms, they can range from mild irritation to severe inflammation. Some people with symptoms get them within 5 to 28 days after being infected. Others do not develop symptoms until much later. Symptoms can come and go.
Men with trichomoniasis may notice:
- Itching or irritation inside the penis;
- Burning after urination or ejaculation;
- Discharge from the penis.
Women with trichomoniasis may notice:
- Itching, burning, redness or soreness of the genitals;
- Discomfort with urination;
- A change in their vaginal discharge (i.e., thin discharge or increased volume) that can be clear, white, yellowish, or greenish with an unusual fishy smell.
Having trichomoniasis can make it feel unpleasant to have sex. Without treatment, the infection can last for months or even years..
What are the complications of trichomoniasis?
Trichomoniasis can increase the risk of getting or spreading other sexually transmitted infections. For example, trichomoniasis can cause genital inflammation that makes it easier to get infected with HIV, or to pass the HIV virus on to a sex partner.
How does trichomoniasis affect a pregnant woman and her baby?
Pregnant women with trichomoniasis are more likely to have their babies too early (preterm delivery). Also, babies born to infected mothers are more likely to have a low birth weight (less than 5.5 pounds).
How is trichomoniasis diagnosed?
It is not possible to diagnose trichomoniasis based on symptoms alone. For both men and women, your health care provider can examine you and get a laboratory test to diagnose trichomoniasis.
What is the treatment for trichomoniasis?
Trichomoniasis can be treated with medication (either metronidazole or tinidazole). These pills are taken by mouth. It is safe for pregnant women to take this medication. It is not recommended to drink alcohol within 24 hours after taking this medication.
People who have been treated for trichomoniasis can get it again. About 1 in 5 people get infected again within 3 months after receiving treatment. To avoid getting reinfected, make sure that all of your sex partners get treated. Also, wait 7- 10 days after you and your partner have been treated to have sex again. Get checked again if your symptoms come back.
How can trichomoniasis be prevented?
The only way to avoid STDs is to not have vaginal, anal, or oral sex.
If you are sexually active, you can do the following things to lower your chances of getting trichomoniasis:
- Be in a long-term mutually monogamous relationship with a partner who has been tested and has negative STD test results;
- Use latex condoms the right way every time you have sex. This can lower your chances of getting trichomoniasis. But the parasite can infect areas that are not covered by a condom - so condoms may not fully protect you from getting trichomoniasis.
Another approach is to talk about the potential risk of STDs before you have sex with a new partner. That way you can make informed choices about the level of risk you are comfortable taking with your sex life.