Q1. Cell survival curves

Suppose you did an experiment to generate a cell survival curve.

a) Describe what steps you would take to do the experiment.

b) What is meant by plating efficiency?

c) In your experiment you irradiate cells using 6 MV photons on a linear accelerator. You collect the data shown in the table below. Plot cell survival as a function of dose and use the linear-quadratic model to fit the data.

d) Determine the alpha/beta ratio from the curve fit. Is this an early responding or late responding cell line?

Two different ant species, Pseudomyrmex and Myrmica, are sometimes found together on the branches of acacia trees. Researchers remove all Pseudomyrmex from one acacia tree. They observe that after removal, the population of Myrmica begins to increase.

From another acacia tree, they remove all Myrmica, and notice that this has apparently no effect on the population of Pseudomyrmex.

Several weeks later, the researchers observe that the tree with no Pseudomyrmex has been grazed to a stump by local tapirs. The tree with no Myrmica and all the acacias with both ant species, remain un-grazed.

In order to test whether there is a mutualistic relationship between acacia trees and Pseudomyrmex, what additional experiment needs to be done?

A

None, the evidence from this observation is enough.

B

A removal experiment in which Pseudomyrmex is placed on a different species of tree

C

A removal experiment in which both species of ant are placed on a different species of tree

D

A laboratory analysis of the chemicals produced by the tree

E

A removal experiment in which tapirs are kept away from the tree

What type of effect might Pseudomyrmex be having on the tapirs?

A

direct positive

B

direct negative

C

indirect positive

D

neutral

1. According to the article, the data was collected through the following means: “For the study, 1,633 participants provided baseline estimates of hand hygiene behaviour and coronavirus infections were identified from nasal swabs…At the start of each season, participants were asked to estimate how many times they had washed their hands the previous day. Frequency of daily hand-washing was subsequently categorized as low, zero to five times daily, moderate, six to 10 times daily, or high, more than 10 times daily.”  

1. Explain why this is an observational study, not an experiment.

2. Identify any potential sources of error in data collection.

3. If scientists were to do this as an experiment, how could they do it? Be specific and address the following concerns.

1. Identify the explanatory variable

2. Identify the response variable

3. Identify how you would choose participants to avoid bias. Consider different types of bias

4. Give a procedure for how the experiment would be run

5. Identify one thing that would be directly controlled

6. Identify an extraneous variable being controlled by random assignment.

7. Would there be a placebo in this experiment? Why or why not?

(I WILL GIVE HIGH RATING I PROMISE)

6. There are 40 books on a bookshelf. Exactly 10 of them have a red cover. The remaining books have a white cover. You intend to choose a random sample of nine books, but you haven't decided whether to choose with replacement or without replacement?

a) If you choose books with our placement, would this procedure lead to independent trials or dependent trials?

b)if you choose books with replacement, would this procedure be consistent with a binomial experiment or not?

c) what is the size of the population? show your work

d) what is the size of the sample? show your work

e) if you ultimately conduct a binomial experiment, find the probability that the 5th book you select, happens to have a red cover? please show your work

f) if you ultimately conduct a binomial experiment, find the probability that you choose two or more red-covered books? please show your work

Finally, for a binomial experiment, please determine: show your work

1. average number of red books, per sample of nine books?
2. the variance of the number of red books, per sample of nine books?

18. One factor that affects the rate of diffusion is_________________________ this factor is

DIRECTLY/ INDERCETLY/ (Circle one) proportional to the rate of diffusion.

19. Listed below are data from osmosis experiment, similar to the one toy conducted in lab a few weeks ago…. Different concentrations were tested and the percent weigh change was measured. Unfortunately, your partner forgot to label the sucrose beakers!

   Percent weight change Data (Mixed up!) +5.3% ; -27.8 ; -7% ; +11.2% ; and -17.5 %

A. Based on what you know about osmosis, match each percent Wt. change with the appropriate / correct OAS concentration.

       Concentration                                    % Wt. change

       .5 M               _________________              

.4 M               _________________               

.3 M               _________________             

.2 M               _________________             

.1 M               _________________                

O M               _________________          

B) Which concentration(s) was/were hypertonic to the potatoes cells?

Experimental design & the scientific method

20. You and your lab partner have decided to address the following question: what is the effect of a high protein diet on the growth of Guinea pigs?

A) What would be an appropriate hypothesis to address the following question?

B) You have decided to do an experiment in which you give four groups of guinea pigs of different amounts of proteins in their diet for four week-period.

What is your independent variable for this experiment? ________________________________

What is your dependent variable for this experiment?   _________________________________

Write an appropriate prediction if your hypothesis is to be supported by the data

21. You carry an experiment in which different batches of seeds are soaked in 5 different salt solutions of decreasing concentration and the percent germination is determined for each batch after 14 days.

Test Your Understanding

Create a JAVA package by name ClassEx2 and in the main() method of
the class, assign your name to a String object and your father name to a
different String object and do the following;

Concatenate your name and your father name.

Get the length of your full name.

Find the index of any character in your full name.

Replace the occurrence of any lower case character in your full
name to capital character.

Compare your first name with your father name , display message
indicating which name is first lexicographically.

A transformer is a device that takes advantage of Faraday’s Law to change an AC voltage. It consists of a primary coil and a secondary coil. When a transformer is used to raise the voltage, it is called step-up transformer and when used to lower the voltage, it is called a step-down transformer. As in the case of nested coils discussed in the Pre-Lab Notes, the secondary coil has a varying magnetic field in its center due to the varying electric current (i.e., AC current) in the primary coil. The induced current and electric potential may be different in the secondary coil than in the primary coil. For N_P loops in the primary coil, N_S turns of the wire in the secondary, and a voltage supplied by the power source of V_P, the induced voltage in the secondary is given by

         (1) V S = N S N P V P

The induced current is

         (2) I S = N P N S I P

The second challenge is to find the ratio of the turns of the outer coil to the inner coil in the nested coil set. The constraint here is that you must use electromagnetic induction in your technique. Another minor limitation is that you don’t have access to the lab equipment. Two data sets are provided for you, You need to analyze them and come to conclusions.

The first data set is for a pair of nested coils, with the inner being the primary with an applied AC voltage at 60 Hz and the outer being the secondary. For the second data set, the primary and secondary roles are reversed.

Copy each of these data sets into Excel, graph them. And find the best fit. Upload the worksheet here.

Dichotomous key for common skin bacteria:
I. Cells arranged in tetrads, glucose not fermented (Micrococcus)
A. Colonies have yellow pigment M. luteus
B. Colonies have red or pink pigment M. roseus

II. Cells arranged in clusters, glucose is fermented (Staphylococcus)
A. Acid produced from mannitol
1. Coagulase-positive S. aureus
2. Coagulase-negative
a. Acid produced from trehalose S. saprophyticus
b. No acid from trehalose S. capitis

B. Acid not produced from mannitol
1. Acid produced from trehalose S. saprophyticus
2. No acid from trehalose S. epidermidis

Elsa completes the in-class lab experiment on skin bacteria by inoculating a phenol red glucose tube and a mannitol salt agar plate with her skin sample. After 24 hours of incubation at 37°C, she performs a Gram stain and phenol red trehalose test on a colony of bacteria from her MSA plate. (Note: the PR trehalose test is similar to the PR glucose test, only the carbohydrate is trehalose instead of glucose).

Elsa’s lab partner, Anna, completes a similar experiment, but with slightly different results. Her initial results point her to a different direction, so instead of completing the PR trehalose test, she completes the coagulase slide test

• Use the dichotomous key on page 41 again to interpret Anna’s results. What is the name of the organism growing on her skin?

4. Is it possible that one or both students have MRSA on their skin? Explain.

An agronomist is conducting a field experiment to identify the best management practice for minimizing spread of a certain plant disease in corn. He compares four different management strategies designed so that they would reduce the spread of the disease. He has set up a field study with a total of 25 experimental plots planted with corn and with 5 treatments (4 disease prevention treatments and a control treatment). Each treatment has been assigned to 5 randomly selected plots. Plant biomass was then measured from each plot at the end of the experiment. The ANOVA table and the treatment means are shown below.

ANOVA:

a)(10 points) Conduct all pairwise comparisons between the treatment means using LSD, (=0.05). Present the results using letters assigned to treatment means (Use letters in the column Letters for part a) in the below table)

b)(10 points) Conduct all pairwise comparisons between the treatment means using Tukey’s HSD (=0.05). Present the results using letters assigned to treatment means. (Use the column Letters for part b) in the below table)

                                                NAME:____________________________

c)(10 points) Did you expect to see differences in conclusions obtained using the two methods (LSD and Tukey’s)? Which method would you use for this analysis? For full credit, provide an explanationof your choice.

Step by step procedure by hand, possibly shortest way to go about this problem would be ideal. thank you in advance