US History Essay Example for Free

US History Essay 4. Describe how prokaryotes carry out photosynthesis and cellular respiration when they lack compartmentalized organelles such as chloroplasts and mitochondria. The area of cellular respiration in prokaryotes is the respiratory membrane. For aerobic prokaryote the infoldings of the plasma membrane are similar to the cristae of mitochondria, whose purpose in eukaryotic cells is cellular respiration. In photosynthetic prokaryotes, the area responsible for cellular respiration is the thylakoid membrane. It functions are similar in manner to chloroplasts in eukaryotic cells. 5. Explain why prokaryotes are unable to grow in very salty or sugary foods, such as cured meats or jam. Prokaryotes have the ability to live harsh environments. Prokaryotes however are unable to live in very salty or sugary foods like cured meats or jams because they lack the essential nutrients that water etc provide. In response to these harsh conditions endospores are formed. In essence, endospores are a touch wall surrounding a set of chromosomes. Eventually as water is removed from the cell its metabolism halts and the rest of the cell disintegrates. In this manner prokaryotes die out in harsh conditions like sugary or salty foods. 6. State the function(s) of each of the following prokaryotic features: a. Capsule i. A capsule is a sticky layer that surrounds the cell wall of some prokaryotes, protecting the cell surface and sometimes helping to glue the cell to surfaces. b. fimbriae ii. A short, hairlike appendage of a prokaryotic cell that helps it adhere to the substrate or to other cells; also known as an attachment pilus. c. sex pilus iii. In bacteria, a structure that links one cell to another at the start of conjugation; also know as a conjugation pilus d. Nucleoid iv. A dense region of DNA in a prokaryotic cell. e. Plasmid v. A small, circular, double stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome. Plasmids are also found in some eukaryotes, such as yeasts. f. Endospores vi. A thick-coated, resistant cell produced by a bacterial cell exposed to harsh conditions. 7. List three factors that give rise to high levels of genetic diversity in prokaryotes. Rapid Reproduction- Rapid reproduction is comparable to a prokaryote reproducing by binary fission repeatedly. After rounds of division most of the offspring cells are identical Mutation- Genetic Recombination- 8. Describe three processes that produce recombinant DNA in prokaryotes.

House on Mango Street Essay -- essays papers

House on Mango Street I never had a choice. They decided it all for me and the next thing you know, we were moved. One night, I come home and my father gives me a big smile and says, we’re out of here. I give him a puzzled look, but after staring into his grinning face, I realize what he means. After thirty nine hard years, he has finally found the home he has always wanted. Since my father was young, he had always dreamed of the house he would one day reside. He would say to his mother, my grandmother, when I get big, I will live in a house as big as New York. When my father began working, he started to save money in the bank, knowing one day it would be spent for his dream home. He would doodle out sketches of how he thought it would look. As he aged, his goal became more realistic. He had a higher paying job, and was able to move out on his own. Knowing he could not just leap into a palace at the ripe age of 19, my father settled down in a run-down apartment complex. He was placed in an old, one bedroom apartment. He would sleep at night, and listen to the other poor families complain and argue into the wee hours. After two years of this, he married my mother and they moved into their first house. This is where I was born and raised. Everything in my life has come from this place. The house was a part of me, and I assumed it would always be there for me. But three days before my sixteenth birthday, everything changes. They have been searching for a new place for months, and my father’s current job gives them the option to look at pretty nice houses. But they claim to have found the greatest bargain of all time. And without my input, they have picked this â€Å"great† house in the middle of nowhere, Wynantskill. So, my father tells me, get ready to say goodbye to your house, we can move to the new place in two weeks. And despite my wishes otherwise, this new place is going to become my home. And when I first see it, it is just as my father has described his house will one day be. He used to sit me down and tell me of the one day when we would move into this gigantic house. He described it as a combination of the White House, a submarine, and a New York City skyscraper. Never worried about how much it would cost, just knowing that one day he would be able to own this residence was all he needed. It’ll make thi... ...up the phone, it rings again. This time it is my father. Hello, son, how are the kids doing? Fine, fine, they are watching TV or something. They’re doing okay. All right, could you put A.J. on the phone? I’d like to ask him something. So I go to get A.J., and I find him bouncing up and down on the couch. I pull him off, and I thrust the phone in his hand. I go back to my room and try to fall asleep when A.J. comes back in, holding the phone outstretched for me. Yeah dad, anything else, I ask. My father tells me that A.J. told him what he and Nick have been doing for the past few hours. So? I say. Well, actually, yes, I was wondering when you are going to get off your lazy butt and actually do something for your family. You’ve been lounging around all day, and the kids still haven’t even eaten lunch yet. I trusted you to watch your brothers to make sure they are okay. But, you can’t take thirty minutes out of your day to play a nice game with them, or even stay awake to make sure they aren’t trying to drink Pine-Sol again. So, you are grounded until I can think of what to do with you. Anything else? Then I hang up the phone and go back to bed

Commercial Brands of Bleaching Solution & a Determination of the Best Buy Essay

Introduction : Sodium chlorate(I) forms the basis of most commercial bleaches. The amount present in bleaching solution can be determined by a volumetric technique. In this experiment, sodium chlorate(I) reacts with excess potassium iodide in the presence of acid to liberate. The iodine is titrated against standard sodium thiosulphate solution. Chemicals : Bleach solution , 0.1 M Na2S2O3 ,1 M H2SO4 , KI , Starch indicator Procedures : 1. Determine the total volume of bleach in the commercial bottles provided. Note the brand name, volume & price of each sample. 2. Pipette 25 cm3 bleach solution into a 250 cm3 volumetric flask. Make up to the mark & mix well. 3. Pipette 25 cm3 of this solution into a conical flask. Add 10 cm3 KI solution & 10 cm3 1 M sulphuric acid. 4. Titrate this mixture against the standard sodium thiosulphate solution provided. Add starch indicator when the solution become pale yellow. 5. Record your results and calculate the molarity of the orginal bleach solution. 6. Determine which bleach has the lowest price per mole of actual bleach. Results : Brand A = ___________KAO_____________ Brand B = _________Best Buy____________ Volume = ___________1.5L______________ Volume = ____________2L_______________ Price = _______$12.9 / Bottle____________ Price = ________$10.9 / Bottle____________ Mole = _________0.753 Mol_____________ Mole = ___________1.152 Mol ___________ $/mole = _______$17.13 / Mol ___________ $/mole = __________$9.46 / Mol__________ Best buy is ________ Best Buy___________ Titration of Brand A against the standard sodium thiosulphate solution Titration 1 2 3 4 Final Burette Reading (ml) 31.70 35.70 27.80 32.20 Initial Burette Reading (ml) 2.90 9.80 4.40 8.30 Volume of titrant (ml) 28.80 25.90 25.40 23.50 Mean volume of titrant (ml) = __(25.90+25.40+23.50)3 = 25.1 ml__ Calculation: The Result Of Brand A Sodium chlorate(I) reacts with excess potassium iodide in the Bleaching solution, which is a acid medium. Iodine solution produced. Following equation: 2H+-(aq) + OCl–(aq) + 2I–(aq) –> Cl–(aq) + I2-(aq) + H2O-(l) Secondly, the iodine solution is titrated with sodium thiosulphate solution Following equation: I2(aq) + 2 S2O32- (aq) –> S4O62- (aq) + 2 I-(aq) The Molarity of Na2S2O3 : = 0.1M Number of mole of S2O3- reacted with I2: : = Molarity X Volume = 0.1 X (25.11000) = 0.00251 mol The Mole ratio of Na2S2O3:: I2= 2:1 Number of moles of I2 reacted with S2O3- = (12) X 0.00251 mol = 0.001255 mol The Mole ratio of NaOCl: I2= 1:1 Number of moles of NaOCl used in the titration = I2 = 0.001255 mol Number of moles of NaOCl in the 250ml volumetic flask = 0.001255 mol X 10 = 0.01255 mol Number of moles in 1.5L bleach solution = 0.01255 mol 25 X 1500 = 0.753 mol Price of OCl- per mole in brand A = $12.9 0.753mol = $17.13 / mol Results : Titration of Brand B against the standard sodium thiosulphate solution Titration 1 2 3 4 Final Burette Reading (ml) 30.90 32.8 31.90 35.20 Initial Burette Reading (ml) 2.10 3.90 3.30 6.90 Volume of titrant (ml) 28.8 28.90 28.60 28.90 Mean volume of titrant (ml) = __(28.90+28.60+28.90)3 = 28.8 ml__ Calculation: The Result Of Brand B Sodium chlorate(I) reacts with excess potassium iodide in the Bleaching solution, which is a acid medium. Iodine solution produced. Following ionic equation: 2H+-(aq) + OCl–(aq) + 2I–(aq) –> Cl–(aq) + I2-(aq) + H2O-(l) Secondly, the iodine solution is titrated with sodium thiosulphate solution Following ionic equation: I2(aq) + 2 S2O32- (aq) –> S4O62- (aq) + 2 I-(aq) The Molarity of Na2S2O3 : = 0.1M Number of mole of S2O3- reacted with I2: : = Molarity X Volume = 0.1 X (28.81000)= 0.00288 mol The Mole ratio of Na2S2O3:: I2= 2:1 Number of moles of I2 reacted with S2O3- = (12) X 0.00288 mol = 0.00144 mol The Mole ratio of NaOCl: I2= 1:1 Number of moles of NaOCl used in the titration = I2 = 0.00144 mol Number of moles of NaOCl in the 250ml volumetic flask = 0.00144 mol X 10 = 0.0144 mol Number of moles in 2L bleach solution = 0.0144 mol 25 X 2000 = 1.152 mol Price of OCl- per mole in brand B = $10.9 1.152 mol = $9.46 / mol Questions : 1. Why must the KI be present in excess ? If less than the specified quantity of KI is added, what effect will this have on the results ? The bleach solution contain sodium chlorate(I),which have ions OCl-.We can prepare the iodine solution by adding the sodium chlorate(I) to potassium iodide in a acidic medium. At first, the sodium chlorate(I) Is the limiting agent. When we add the excess potassium iodide into the bleach solution. Not only it will not effect the result, but also the calculation can be more accurate. All the ions OCl- can be completely reacted. In addition, Iodine solution is only slightly soluble in water but it is very soluble in the solution, which contain I- ions. 2. What is the function of the sulphuric acid ? The function of sulphuric acid is provide a acidic medium containing excess iodide to ionizes the iodine solution to triiodide ions. We must know that the Brown colour of iodine solution is cause for the triiodide ions(I3-).This colour in observation of titration is very important. 3. Bleaching solutions may deteriorate for 2 reasons : (a) react with CO2 in the air according to the equation : 2 OCl- + CO2 –> CO32-+ H2 + Cl2 (b) what is the other reason ? It must be effected by light. It is because the The hypochlorite ions OCl-( will be decompose quickly under light Following equation:2NaOCl –>2NaCl + O2, .While losing some OCl- ions, the result in calculation will not be accurate 4. What should the starch indicator not be added too early ? The starch solution turns the iodine to blue black because of the formation of starch-iodine complex. Also, the complex is not reversible when the concentration of iodine is high. If we add the starch solution early, the attraction of starch molecules and iodine molecules will attract so strongly. Although we have add standard sodium thiosulphate solution, but we can not do completely finish the real result of titration and effecting the calculation. The above-mentioned tell us that the starch solution should be added when only a few of iodine solution left, near the end point of the titration.

Levels and Scales of Measurement in Statistics

Level of measurement refers to the particular way that a variable is measured within scientific research, and  scale of measurement refers to the particular tool that a researcher uses to sort the data in an organized way, depending on the level of measurement that they have selected. Choosing the level and scale of measurement are  important parts of the research design process  because they are necessary for systematized measuring and categorizing of data, and thus for analyzing it and drawing conclusions from it as well that are considered valid. Within science, there are four commonly used levels and scales of measurement: nominal, ordinal, interval, and ratio. These were developed by  psychologist Stanley Smith Stevens, who wrote about them in a 1946 article in  Science, titled On the Theory of Scales of Measurement. Each level of measurement and its corresponding scale is able to measure one or more of the four properties of measurement, which include identity, magnitude, equal intervals, and a minimum value of zero. There is a hierarchy of these different levels of measurement. With the lower levels of measurement (nominal, ordinal), assumptions are typically less restrictive and data analyses are less sensitive. At each level of the hierarchy, the current level includes all the qualities of the one below it in addition to something new. In general, it is desirable to have higher levels of measurement (interval or ratio) rather than a lower one. Let’s examine each level of measurement and its corresponding scale in order from lowest to highest in the hierarchy. The Nominal Level and Scale A nominal scale is used to name the categories within the variables you use in your research. This kind of scale provides no ranking or ordering of values; it simply provides a name for each category within a variable so that you can track them among your data. Which is to say, it satisfies the measurement of identity, and identity alone. Common examples within sociology include the nominal tracking of  sex (male or female),  race  (white, Black, Hispanic, Asian, American Indian, etc.),  and class  (poor, working class, middle class, upper class). Of course, there are many other variables one can measure on a nominal scale. The nominal level of measurement is also known as a categorical measure  and is considered qualitative in nature. When doing statistical research and using this level of measurement, one would use the mode, or the most commonly occurring value, as a  measure of central tendency. The Ordinal Level and Scale Ordinal scales are used when a researcher wants to measure something that is not easily quantified, like feelings or opinions. Within such a scale the different values for a variable are progressively ordered, which is what makes the scale useful and informative. It satisfies both the properties of identity and of magnitude. However, it is important to note that as such a scale is not quantifiable—the precise differences between the variable categories are unknowable. Within sociology, ordinal scales are commonly used to measure peoples views and opinions on social issues,  like racism  and sexism, or how important certain issues are to them in the context of a political election. For example, if a researcher wants to measure the extent to which a population believes that racism is a problem, they could ask a question like How big a problem is racism in our society today? and provide the following response options: its a big problem, it is somewhat a problem, it is a small problem, and racism is not a problem. When using this level and scale of measurement, it is the median which denotes central tendency. The Interval Level and Scale Unlike nominal and ordinal scales, an interval scale is a numeric one that allows for ordering of variables  and provides a precise, quantifiable understanding of the differences between them (the intervals between them). This means that it satisfies the three properties of identity, magnitude,  and  equal intervals. Age is a common variable that sociologists track using an interval scale, like 1, 2, 3, 4, etc. One can also turn non-interval, ordered variable categories into an interval scale to aid  statistical analysis. For example,  it is common to measure income as a range, like $0-$9,999; $10,000-$19,999; $20,000-$29,000, and so on. These ranges can be turned into intervals that reflect the increasing level of income, by using 1 to signal the lowest category, 2 the next, then 3, etc. Interval scales are especially useful because they not only allow for measuring the frequency and percentage of variable categories within our data, they also allow us to calculate the  mean, in addition to the median, mode. Importantly, with the interval level of measurement, one can also calculate  the standard deviation. The Ratio Level and Scale The ratio scale of measurement is nearly the same as the interval scale, however, it differs in that it has an absolute value of zero, and so it is the only scale that satisfies all four properties of measurement. A sociologist would use a ratio scale to measure actual earned income in a given year, not divided into categorical ranges, but ranging from $0 upward. Anything that can be measured from absolute zero can be measured with a ratio scale, like for example the number of children a person has, the  number of elections a person has voted in, or the  number of friends who are of a race different from the respondent. One can run all the statistical operations as can be done with the interval scale, and even more with the ratio scale. In fact, it is so called because one can create ratios and fractions from the data when one uses a ratio level of measurement and scale. Updated  by Nicki Lisa Cole, Ph.D.