A General Review of Tetracyclines Antibiotics Chang Liu Instructor: Prof. Jasson Sello Department of Chemistry‚ Brown University Providence 02906‚ RI Tetracyclines are the first broad-spectrum antibiotic to be applied to clinic use. Nevertheless‚ the increasing incidence of bacterial resistance of tetracyclines led to a series of studies on the development of semisynthetic tetracyclines to circumvent the resistant organisms. In order to better design the structures of tetracycline derivatives
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Both prokaryotic cells that create bacteria and eukaryotic cells that make up most other forms of life evolve. Natural selection and genetic variation are simply the way evolution happens. This is why there is an antibiotic resistance. If bacteria are constantly changing then antibiotics must change too. Evolution is an amazing process that explains and justifies change. In New Mexico at the Carlsbad Caverns National Park there is a unique and enlightened discovery. There are many caves in the
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Batteries‚ Resistance and Current “Battery-Resistor”: Check “show battery” and “show cores”‚ watch what happens‚ adjust some variables 1. Why do electrons (blue dots) move? Draw a diagram of the battery‚ label the flow of electrons. The flow of current (+) is opposite; draw this and note if toward or away from + terminal of the battery. The blue dots indicating the electrons move because there is a voltage across the battery in which the electrons flow away from the positive terminal
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scale divisions which can be read to half a division. Determine resolution of meter in volt. [0.25 V] (c) A Wheatstone bridge is balanced with all the four resistances equal to 1kΩ each. The bridge supply voltage is 100V. Now one of the resistances is changed to 1010Ω. The output voltage is measured by a voltmeter of infinite resistance. Calculate the bridge sensitivity. [25V or 0.025 V/Ω] (d)Each of the following numbers has a uncertainty of one in the last figure. Determine the number of significant
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Resistance in a Conductor: The electrical resistance of an electrical conductor is the opposition to the passage of an electric current through that conductor. Electrical resistance shares some conceptual parallels with the mechanical notion of friction. The SI unit of electrical resistance is the ohm (Ω).An object of uniform cross section has a resistance proportional to its resistivity and length and inversely proportional to its cross-sectional area. All materials show some resistance‚ except
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Introduction The resistance of a wire depends on certain factors. Some of these variables are listed below: Length of wire Diameter or thickness of wire Temperature at which wire is kept The material of which wire is made out of. The potential difference or voltage. Humidity Cross sectional area. Voltage across circuit All these factors will have to be kept constant except the diameter of the wire whilst doing the experiment to ensure that the investigation is
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ELECTRICITY HOTS Questions for Practice 1. Name a substance whose resistance almost remains unchanged by increase of temperature. 2. Name two special characteristics of heater coil. 3. A wire of resistance 4 ohms is bent to form a circle. What is the resistance between two diametrically opposite ends? 4. How does the resistance of a conductor change if its temperature is increased? 5. A current of 4A flows in a wire of resistance 60 ohms. Calculate electrical energy consumed in 2 minutes. 6. V-I
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Out of the darkness of the French defeat and capitulation of 1940 rose one of the greatest mass-resistance movements in history. Thousands of French patriots rose up‚ by themselves and in groups‚ and defied Nazi authority. They formed resistance movements that fought the Nazi occupation of France and the collaboration of the Vichy government. The French resistance was detrimental to the success of the Allies during World War II because they played a key role in the D-Day landings and were able to
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Jewish Resistance We must first realize that resistance was in no way a survival strategy. Yet‚ even when it seemed obvious that death was near inevitable‚ why did they not put up a fight? This argument is still puzzling to many holocaust historians‚ yet the arguments of Raul Hilberg and Yehuda Bauer offer insight to possible reasons why they did not fight and that resistance was more widespread than most people think. First of all we will look at Raul Hilberg’s “Two Thousand Years
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The resistance of a wire Planning:- Introduction: To investigate the resistance of a wire at different lengths to see whether or not a longer wire has a larger resistance than a shorter wire. Apparatus: Wire Voltmeter Ammeter Battery 2 crocodile clips Metre rule Variable resistor Diagram: Variables: Length Thickness Resistance Material The material and diameter of the wire needs to be kept constant to keep the test fair as we are investigating resistance. The
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