An extract on #spreadpositivity
Pressure-swing distillation is essentially the same as the unidirectional distillation used to break azeotropic mixtures, but here both positive and negative pressures may be employed.
This improves the selectivity of the distillation and allows a chemist to optimize distillation by avoiding extremes of pressure and temperature that waste energy. This is particularly important in commercial applications.
One example of the application of pressure-swing distillation is during the industrial purification of ethyl acetate after its catalytic synthesis from ethanol.
Constipation occurs in nearly half of people with Down syndrome and may result in changes in behavior. One potential cause is Hirschsprung's disease, occurring in 215%, which is due to a lack of nerve cells controlling the colon. Other frequent congenital problems include duodenal atresia, pyloric stenosis, Meckel diverticulum, and imperforate anus. Celiac disease affects about 720% and gastroesophageal reflux disease is also more common.
When screening tests predict a high risk of Down syndrome, a more invasive diagnostic test (amniocentesis or chorionic villus sampling) is needed to confirm the diagnosis. If Down syndrome occurs in one in 500 pregnancies and the test used has a 5% false-positive rate, this means, of 26 women who test positive on screening, only one will have Down syndrome confirmed. If the screening test has a 2% false-positive rate, this means one of eleven who test positive on screening have a fetus with DS. Amniocentesis and chorionic villus sampling are more reliable tests, but they increase the risk of miscarriage between 0.5 and 1%. The risk of limb problems is increased in the offspring due to the procedure. The risk from the procedure is greater the earlier it is performed, thus amniocentesis is not recommended before 15 weeks gestational age and chorionic villus sampling before 10 weeks gestational age.
Some obstetricians argue that not offering screening for Down syndrome is unethical. As it is a medically reasonable procedure, per informed consent, people should at least be given information about it. It will then be the woman's choice, based on her personal beliefs, how much or how little screening she wishes. When results from testing become available, it is also considered unethical not to give the results to the person in question.
Some bioethicists deem it reasonable for parents to select a child who would have the highest well-being. One criticism of this reasoning is that it often values those with disabilities less. Some parents argue that Down syndrome shouldn't be prevented or cured and that eliminating Down syndrome amounts to genocide. The disability rights movement does not have a position on screening, although some members consider testing and abortion discriminatory. Some in the United States who are pro-life support abortion if the fetus is disabled, while others do not. Of a group of 40 mothers in the United States who have had one child with Down syndrome, half agreed to screening in the next pregnancy.
Within the US, some Protestants denominations see abortion as acceptable when a fetus has Down syndrome, while Orthodox Christians and Roman Catholics often do not. Some of those against screening refer to it as a form of "eugenics". Disagreement exists within Islam regarding the acceptability of abortion in those carrying a fetus with Down syndrome. Some Islamic countries allow abortion, while others do not. Women may face stigmatization whichever decision they make.