The p24 antigen test can detect the p24 protein on average 10 to 14 days after infection with HIV.2,3,11,12 One drawback of this test is that levels of the p24 protein peak at around three to four weeks after exposure to HIV and are usually not detectable after five to six weeks (and sometimes even earlier).
Liquid nitrogen is nitrogen in a liquid state at an extremely low temperature.It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colorless clear liquid with density of 0.807 g/ml at its boiling point and a dielectric constant of 1.43.iquid nitrogen is nitrogen in a liquid state at an extremely low temperature.
Nitrogen from the top of the low-pressure column is compressed, cooled, and expanded to liquefy the nitrogen. This liquid nitrogen stream is then fed back into the low-pressure column to provide the additional cooling required to liquefy the oxygen as it sinks to the bottom of the column. 11 Because liquid oxygen has a high boiling point, it boils off rapidly and is rarely shipped farther than 500 mi (800 km).