Ethanol is to be used as a substrate for single-cell protein production in a chemostat. The available equipment can achieve an oxygen transfer rate of 10 g O₂/l of liquid per hour. Assume the kinetics of cell growth on ethanol is of the Monod type, with µm = 0.5 h^–1, K_s = 30 mg/l, YX/S = 0.5 cells/g ethanol, and YO2/S = 2 g O2/g EtOH. We wish to operate the chemostat with an ethanol concentration in the feed of 22 g/L. We also wish to maximize the biomass productivity and minimize the loss of unused ethanol in the effluent. Determine the required dilution rate

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#Question id: 4955

#SCPH28 | Zoology

If relatively small carbonaceous chondrites from space were a significant source of Earthʹs original amino acids, then which two of these would have been most important in permitting their organic materials to survive impact with Earth?

I. Carbonaceous chondrites must contain no D-amino acids.

II. Earthʹs early atmosphere must have had little free oxygen.

III. The chondrites must have arrived on Earth before 4.2 billion years ago.

IV. Earthʹs early atmosphere must have been dense enough to dramatically slow the chondrites before they impacted.

V. The chondrites must have impacted land, rather than a large body of water.

#Question id: 4956

#SCPH06 I Botany

Which measurement would help determine absolute dates by radiometric means?

#Question id: 4956

#SCPH28 | Zoology

Which measurement would help determine absolute dates by radiometric means?

#Question id: 4957

#SCPH06 I Botany

How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil at the time of analysis?

#Question id: 4957

#SCPH28 | Zoology

How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil at the time of analysis?

#Question id: 4958

#SCPH06 I Botany

What is true of the fossil record of mammalian origins?