1. a grad student has a culture of e. coli with a total volume of 600 ml, and od reading at 550 nm of 1.7. he makes serial dilutions of the culture, starting with a transfer of 1 ml culture into 9 ml tryptone broth. next, he transfers 0.1 ml of this dilution into 0.9 ml tryptone broth, and repeats this two more times to make a total of 4 serial dilutions. he the he then pipets 200 ul from the fourth dilution on an agar plate, spreads it over the surface, and puts the plate in an incubator to grow overnight. the next day, he counts 386 cfus (colony forming units) on the plate.

a. what is the dilution in the third tube? answer with the exponent to the power of 10, that is ? in 10?

b. what is the dilution of cells spread onto the agar plate? answer in decimal notation.

c. how many viable cells are present in the 1,800 ml starting culture? answer in decimal notation.

1. loamy sand is about 80% sand with 10% clay and defined mostly by sand particles with some clay to provide structure and fertility. the sand particles are easily visible and the soil holds structure but breaks apart easily.

2. scott sand can improve his soil quality by incorporating more silt and organic matter into the soil. peat moss and organic matter can also be incorporated.

hypoxemia refers to a below usual concentration of oxygen in the blood, mainly in the arteries. hypoxemia is an indication of an issue associated with circulation or breathing and may lead to various symptoms like shortness of breath.  

the condition is identified by determining the level of oxygen in the blood sample obtained from an artery. it can also be predicted by determining the oxygen saturation of the blood with the application of a pulse oximeter.  

the normal arterial oxygen is about 75 to 100 mm hg. the values underneath 60 mm hg is generally considered with the requirement for supplemental oxygen. the normal pulse oximeter readings generally range between 95 to 100 percent. the values under 90 percent are regarded as low.  

in the given case, the oxygen saturation is measured at 93 percent, hence, there is no need to administer oxygen, that is, one should withhold oxygen.