a dilute disinfection kils 90 %of a bacterial inoculum in 10 min.
Which of the following is the shortest amount of time in min reguered to reduce an inoculum 10^9 bacteria to lss than 10
a 10
b 50
c100
d 140
e 180
please help me calculate it
drjvenkatesh - 07/27/10 19:11
its saying 90% of bact. reduced in 10 mins ..
total bact = 10^9 then after 10 mins - 90% killed and 10 % remaining - so then 10^9 * 10% = 10^8
then after 20 mins 10^7, 30 mins 10^6, 40 mins 10^5, 50 mins 10^4, 60 mins 10^3, 70 mins 10^2, 80 mins 10^1, 90 mins 1, 100 mins 0.1 .....
so min time to reduce 10^9 bact to lesss than ten is 100 !!!!
http://www.usmleforum.com/showthread.php?tid=521626 (ans for below qs)
18. A randomized, double-blind, controlled trial is conducted to assess the efficacy of a drug to prevent osteoporotic fractures in women older than 65 years. Sixty women are enrolled; 30 subjects receive the new drug (group X), and 30 subjects receive a placebo (group Y). Two years later, seven subjects from group X have had fractures, and 15 subjects from group Y have had fractures (p=0.06). The investigators conclude that there is not a significant difference between the treatments, and the new agent is not recommended. Which of the following raises the most concern about the validity of this conclusion?
A ) Inappropriate study population
B ) Low external validity
C ) Low power
D ) Use of blinding
E ) Use of a placebo
Q-12) The graph shows serum penicillin G concentrations after patients X and Y are given penicillin G, 250 mg orally. Patient X is an otherwise healthy 30 year old man. Which of the following best explains the findings for the patient Y?
A) Achlorhydria
B) Concomitant use of cimetidine
C) Decreased protein binding
D) Intestinal malabsorption
E) Renal insufficiency