PCS 125 Physics: Waves and Fields

Transcription

1 PCS 125 Physics: Waves and Fields Catherine Beauchemin Fall URL: cbeau

2 A few words about your instructor REMEMBER: Your instructor s name is Catherine Beauchemin Upon my arrival at Ryerson University, I founded my research group: Phymbie, for Physical Modelling in Biology, Immunology, and Ecology. My group will do research in the area of computational/mathematical modelling of self-organizing systems, with a particular interest in modelling dynamics of infectious diseases within a host and host/immune interactions.

3 Influenza modeling project Project Develop a set of tools for influenza research: an accurate agent-based model for an influenza infection in vitro a suite of experimental assays performed on human lung cell monolayers infected with influenza providing the data needed to calibrate the agent-based model Short Term Goals Use these tools synergetically to study how the spatial spread of influenza on a human lung cell monolayer is affected by: Interferon, a chemical substance secreted by infected cells which prevents viral entry into uninfected cells. Human lung cell receptor diversity. Different cell types (e.g. ciliated, secretory) have different infection and viral production rates. Anti-influenza drug and the emergence of drug resistance. Long Term Goal Use these refined tools to rapidly predict the virulence of a newly isolated influenza strain

4 Influenza modelling: The experimental model Done by Frederick Koster (Lovelace Respiratory Inst.). Monolayers of 1.2 million human lung epithelial cells are inoculated with influenza virions. The information collected: number of virions; proportions of cells infected; binary autocorrelation of infected/uninfected cells.

5 Influenza modelling: The agent-based model A 2-D hexagonal grid where: Each site is an epithelial cell which can either be uninfected (white), dead (black), or infected (red or green). Infected cells secrete virus (magenta) which infect new cells.

6 I also really like ants! Ants are a great example of self-organizing systems where the interactions between the simple agents of the collective systems gives rise to intelligent behaviours: decision making, learning, and memory.

7 What about you? Many of you may be new to Ryerson, and probably don t know anyone here. Please take a minute to get to know the person sitting to your right and to your left. Perhaps exchange that will be helpful later in the semester!

8 Your first class! Welcome to your first university physics class. Here are a few thing you really need to remember: REMEMBER: Your instructor s name is Catherine Beauchemin Know when to be where, e.g. PCS PCS125 is the code name for your course 16 is your section number (either 15, 16, 17, or 18) 1 is the course component (1=class, 2=lab, 3=tutorial) Take responsability: you are not in high school anymore. Your success is entirely dependent on YOU! Seek help as soon as you see your marks dropping. You should be spending at least 8 h/wk on this class: 3 h/wk on lectures 1.5 h/wk on labs (2h lab + 1h report per 2 wk) 0.5 h/wk on tutorial/quiz (1h per 2 wk) 3 h/wk reading textbook and doing the problems

9 Your lab and tutorial schedule

10 Your resources Closely examine your Course Management Form and keep it safe. It is a binding agreement that both you and your instructor have entered. Your Course Outline details all the subjects you are expected to know. You absolutely MUST activate and regularly check your Ryerson Matrix account. I will be sending you important information by and you are responsible for checking it. If you miss something because you did not check your , it will be your responsability. I will be holding fixed office hours. During office hours, you can come in at any time, unannounced and get help. My office hours are: Tuesdays, 3pm - 5pm Wednesdays, 2pm - 4pm If you absolutely must see me outside office hours, you must set up an appointment by (cbeau@ryerson.ca). If you come unannounced outside of office hours, I might not help you. Questions on assignments, marks, documents used in class, and perhaps notes will all be available to you through Blackboard at (log in with Matrix ID and Pwd).

11 Blackboard: my.ryerson.ca From online courses tab select PCS 125. From the left-hand side menu select Instructor-specific content, select Catherine Beauchemin. There you will find my contact info, link to the discussion forum for our class, and any documents discussed in class.

12 O.K., let s start!

13 Chapter 1: Physics and Measurements Pages 1 18 in your textbook. The concept of units is probably more central to physics than to any other science. Units give physical meaning to a number and allow you to verify that your equation makes physical sense. Le Système International d Unités (SI) is the international committee which establishes the standards for the fundamental quantities of science such as length, mass, time, etc. These standard units are refered to as SI units. One example of the importance of agreed units is the failure of the NASA Mars Climate Orbiter, which was accidentally destroyed on a mission to the planet Mars in September 1999 instead of entering orbit, due to miscommunications about the value of forces: different computer programs used different units of measurement (newton versus pound force). Enormous amounts of effort, time, and money were wasted. A measurement without units has no value and use of units needs to follow standards!

14 Chapter 1: Physics and Measurements Section 1.1: Standards of Length, Mass, and Time Length: meters (m) the distance traveled by light in vacuum during a time of 1/299, 792, 458 s. Mass: kilogram (kg) the mass of a specific platinum-iridium alloy cylinder kept at the International Bureau of Weights and Measures at Sèvres, France. Time: second (s) atomic clock: 9,192,631,770 times the period of vibration of radiation from the cesium-133 atom. Temperature: kelvin (K) precisely 1/ parts the difference between absolute zero and the triple point of specifically defined water. One kelvin has precisely the same magnitude as a one-degree increment on the Celsius scale and the difference between the two scales null points is precisely K (0 K = C and K = 0.01 C).

15 Chapter 1: Physics and Measurements Section 1.1: Standards of Length, Mass, and Time Scientific notation: Physics is probably the field which studies phenomenon over the vastest range of sizes. When dealing with the extremely small (electrons) and the extremely large (solar systems), certain numbers are simply not practical to write out. The age of the universe is 500, 000, 000, 000, 000, 000 s. Using scientific notation, this is simply s. The exponent simply gives you the number of digits after the.. Here, we have 17 zeros after the period. A few quick examples: = = = 68 Scientific notation is also used in order to clearly identify the number of figures (digits) we actually know. These digits are called significant figures or digits and you will hear a lot about them in your labs.

16 Chapter 1: Physics and Measurements Table 1.4: Unit prefixes (p.6) Although I do not encourage you to use them (the use of scientific notation is prefered), there are also standard unit prefixes you will encounter in the literature and in your everyday life. Here are some of the common ones: Prefix Symbol Spoken Numeric Scientific peta P quadrillionth tera T trillion giga G billion mega M million kilo k thousand deci d tenth centi c hundredth milli m thousandth micro µ millionth pico p billionth femto f trillionth atto a quadrillionth

17 Chapter 1: Physics and Measurements Section 1.3: Dimensional analysis The word dimension has a special meaning in physics: it denotes the physical nature of the quantity. A distance can have various units (meter, feet, etc.), but it will always have dimensions of length. The units meter, feet, are all units of length: seeing them means that you are dealing with a length. This is why I said that units inform you on the physical nature of the number it follows. Doing a dimensional analysis is a great way to verify if you ve made any mistakes in your equation. Let s work through an example: Analysis of a power law: Find the value of m and n in a = kr n v m which gives the acceleration a of a particle moving with uniform speed v in a circle of radius r, where k is a dimensionless proportionality constant.

18 Chapter 1: Physics and Measurements Section 1.4 & 1.6: Conversion of Units and Significant Figures By keeping track of your units, conversion from one set of unit to another is much simpler and is more reliable. When adding/subtracting quantities, the number of decimal places in the results should equal that of the term with the smallest number of decimal places. (e.g = ). When multiplying/dividing quantities, the number of significant figures in the results should equal that of the term with the smallest number of significant figures. (e.g = ). For proper precision, you should only ever round-off your calculation when stating your answer: Do not round-off in the intermediate steps. As a general rule: You should never say more than you know (this probably should apply to more aspects of your life than just physics!) A summarizing example: If I know that you are 18 years old and I want to quote your age in seconds, how would I do this?