model
dr. dolittle | June 24, 2017 Photo of zebrafish housed at a research institute. By Karol Głąb CC BY-SA 3.0. via Wikimedia Commons
Who would have thought tiny fish could lead to big advances in medicine? Zebrafish (Danio rerio) and mammals have similar anatomy and physiology of the brain, eyes, gut, and cardiovascular systems. Some of the reasons why these fish are good models to understand cardiovascular physiology were recently explored in a new article published in Physiological Reviews.
Animal models are used in research that seeks to understand both normal physiological mechanisms as well as mechanisms related to…
dr. dolittle | October 20, 2015 Image of Drosophila from Wikipedia.
A new study published in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology describes how Drosophila melanogaster develop similar heart complications as humans when they become obese. Rather than feeding them a high fat diet to induce obesity, researchers selected flies that were resistant to starvation over 65 generations. The so-called starvation resistant Drosophila had dilated hearts that had an impaired ability to contract. Interestingly, the problem was caused by fat deposits literally shifting the position of…
dr. dolittle | October 10, 2014 Image from the American Physiological Society's website.http://www.the-aps.org/mm/Conferences/APS-Conferences/2014-Conferences/…
Wednesday was the last day of the meeting that culminated in a closing banquet with an awards session to honor students who had exceptional presentations. What an impressive group of young comparative physiologists! The plenary lecture was given by Dr. Steven Chown (Monash Univ, Australia). He spoke about climate change forecasts and continuing environmental changes and how important it is to understand how animals adapt to changing conditions in order to make…
drorzel | August 31, 2010Back in July, I did a post looking at how the fountain in our ornamental backyard pond shoots higher when the level of the pond drops. I set up a simple model of the process, which worked surprisingly well, but I said at the time that I really needed more data to say whether that agreement was real or accidental. Well, yesterday, I got some extreme data:
The leak in the pond has gotten worse, I think, and the water was barely covering the top of the pump box at all. A very rough calibration of this image, using the fact that the brick is 2in high, gives a height of the spray of about 62in,…
rallain | August 24, 2010I might as well make a new tag called "basketball throws" because I can't stop with the analysis of these crazy basketball shots. Watch - in the end someone is going to post a video about how all these were faked (and I have said there is no clear evidence they are fake). Oh, if you want to see some shots that I am talking about - just search for Dude Perfect on youtube.
Physically, these crazy shots are possible. Time of flight in the video is comparable to a numerical model. But, the question is: how difficult are these shots? Are these one in a million? Are they easy? Are they…
rallain | July 8, 2010In my last zombie post, I looked at a human moving in a circle to avoid a zombie (if they are stuck in a room). What if I build a zombie evading robot that always moves perpendicular to the path of the zombie? Would this work?
This shouldn't be too difficult to model. I can use my existing model for the zombie (where there is a force towards the human and a drag force). For the right-turning-robot, I will also have a drag force and a "driving" force. How do I find the direction of the driving force for the robot? Here is a diagram.
This Fdrive force will really be the frictional force…
rallain | July 1, 2010Title: Chased by zombies
When I heard word about the ScienceBlogs Zombie Day, I knew I wanted to participate with a post - but I had no idea what to do. My first thought was to somehow talk about living off the electric grid in the case of a zombipocolypse - you know, like how big of a solar panel would you need?
But you know what? Physics is difficult - but modeling is easy. How about I model something? How about a model for the motion of a zombie horde? This will be great.
Zombie motion model
What do I want in my model? What are the constraints? What real-life situations can I use to…
rallain | June 9, 2010Here is another question from Ask a ScienceBlogger. Reader Uday Panta asks:
How does water evaporate in the seas? Doesn't water evaporate at 100 C?
There were some very good responses in the comments where the question was, but I am going to answer it with some more details.
Small Particle Model
This is where we need to start - the small particle model of liquids and gases. This model treats the liquid as being made up of a lot of particles (well, obviously). If there is a gas (or liquid) at a certain temperature, then there are particles moving around at different speeds. Often it is…
rallain | May 31, 2010So suppose you saw something that looked like this:
This is a ball shot out of a shooter device. Well, it is a vypthon animation of a ball. What would you do if you came to see this video? If I had not made it, I would say it is an unrealistic video. It does not agree with my basic model of how things move after being thrown or shot or whatever. Interestingly (but unrelated) there was a set of physics questions that showed different possible paths of a thrown ball. The path representing the motion above was a common choice.
Like I said, I made that animation. Here is another one. In…
rallain | May 24, 2010While I am still fresh on the Space Jump topic, let me take it to the extreme. Star Trek extreme.
SPOILER ALERT
But really, is this a spoiler alert if it is from the trailer of a movie that has been out forever? Of course, I talking about the latest Star Trek movie where three guys jump out of a shuttle and into the atmosphere.
So, in light of the Red Bull Stratos jump, how would this jump compare? First, my assumptions:
This Star Trek jump is on the planet Vulcan. I am going to assume this is just like Earth in terms of gravity and density of air.
The jumpers in Star Trek have on stuff…
rallain | April 26, 2010I meant to mention this earlier since it happened a little while ago. There is this "mini-conference" with three schools: Southeastern Louisiana University, Southern Mississippi University, and the University of South Alabama. The purpose is to give students (and some faculty) a chance to present their work at a smaller conference. I really enjoy this, mostly because it is small and I get to see lots of undergrad talks. There are two talks that stuck in my head.
Dr. Jiu Ding "Dynamical Geometry: From Order to Chaos and Sierpinski Pedal Triangles"
Jiu Ding is a mathematics professor at…
rallain | December 15, 2009Maybe you have noticed how much material there was (for me at least) in last week's MythBusters. One of the myths they looked at was the bus jumping over a gap in the road from the movie Speed. I am not looking at that myth, it has been discussed many times in many places. Rather, I am going to talk about scaling the motion. As typical with the MythBusters, they like to make a scaled down version of the event. It's cheaper that way. In this case, they made a 1/12th scale model of the bus and the road. The question was: how fast should the model go?
The first question to ask is: what do…
rallain | December 10, 2009This picture has been all over the blogs.
I don't want to talk about this picture too much - that has been done (a good summary discussion can be found at Bad Astronomy). Apparently, this is some type of rocket mistake or something.
Although the picture is cool, it is not as cool as this simulation that someone made.
Here is the best shot from the video:
Maybe that picture didn't turn out so well. The point is that someone made a simulation (I assume it is a simulation, and not just an animation). How do you know if a simulation is any good? You look and see how well it compares with…
rallain | December 9, 2009This is a requested post. Clearly, I do requests. The idea here is that I am going to give all the details needed to determine the equation of motion (and then model it) for a basic pendulum. Warning: this post is a little more advanced than my normal posts. There are some prerequisites. You need to understand derivatives. I will assume that you do. Here is a pendulum. (and this time I will stick to my variables)
Like I said before, this is a tricky problem unless I use some tricks. The problem is that the tension the string exerts on the mass changes. Here is my trick: think about a…
rallain | November 13, 2009Not really. Here are the details (and some data) for the Millikan Oil Drop Experiment without the oil drop that I talked about previously (originally from The Physics Teacher - lucky you, it was a featured article so it should still be available (pdf)).
The basic idea that Lowell McCann and Earl Blodgett from U of Wisconsin propose is to do an experiment similar to the oil drop experiment, but not so squinty (if you have done the oil drop experiment, you know what I mean). Instead of dropping charged oil in an electric field, they drop containers with metal nuts in water. The goal is to…
rallain | November 4, 2009I already attacked the 2008 Punkin Chunkin Show. So, now I going to give the chunkers some tips. In case you aren't familiar, the Punkin Chunkin contest has teams create devices to launch a pumpkin. They have different categories, but I am going to focus on the air-powered devices. The basic idea is to make an over sized pneumatic potato gun. Here are the things I was inspired to think about.
It seems all the canons were aimed at about the same angle. Did they guess at the angle? Or is this trial and error? What would be the best angle for a pumpkin launch?
Does the optimal angle of…
rallain | September 4, 2009I love this story. It is a story of how ideas changed about the nature of the atom. These are the notes (and diagrams) I use when I teach the atomic nature of matter to non-science majors. The best thing about this story is that it is a great example of science. Science (or scientists) build a model. If new evidence comes along, the model gets changed. There are several other websites that describe all of this stuff, I will list a couple at the end of this post.
Typical textbook model of an atom
Look in an intro, non-science majors textbook and you will probably see a picture like this…
rallain | August 17, 2009I have been reflecting on my recent failure to realize that the Giant Water Slide Jump was fake (more analysis here). I think the guys that made this video did a really good job on several levels. First, the motion appears to do two important things:
shows constant acceleration in the vertical direction
shows constant velocity in the horizontal direction
That seems like such a simple thing, but it is surprising how often fake videos don't have those two elements. Maybe they were not close, but with the error associated with the panning and zooming camera, it seemed close enough. Also, to…
rallain | August 3, 2009Every introductory astronomy text and most intro physics texts talk about tides. The usual explanation is something along the lines of:
The moon exerts a gravitational force on the Earth and all the stuff on the Earth.
This force decreases with distance (1/r2).
Thus the moon pulls greater on one side of the Earth than the other
This doesn't matter except for oceans which can move.
BOOM. Two tides a day due to a bulge on the side close to the moon and the opposite side.
Oh, the Earth is slowing down.
Really, that is what almost all intro texts say. Go check for yourselves.
Yes, the tides…
rallain | May 19, 2009Some of the other blog sites have talked about physics vs. chemistry. It seems this started with The experimental Error blog. Tom at Swans on Tea added a very excellent point to the discussion and the discussion continues at Uncertain Principles.
So, here is my take on the subject. Physics essentially deals with the fundamental stuff. You know, Maxwell's equations, the four forces, the particles, quantum mechanics. Chemistry is the study of substances and their interactions. First, let me attack chemistry. Here are some things I don't like:
Photo electron. What is a photo electron?…