My lecture professor listed purifying selection under positive frequency-dependent selection. She gave the example of wing color in Heliconius as an example. Diversifying selection was listed under negative frequency-dependent selection and the example of the human influenza virus was given as an example.
My question is, is this correct? Because when asking us to analyze a paper on Ebola, she said to find the difference between positive and purifying selection and she put diversifying selection in parentheses after positive selection, not negative selection. So now I'm confused.
I would ask her this myself but she does not respond to email.
I'm trying to get a handle on the difference between multiple niche polymorphism and negative frequency dependent selection. In Brisson and Dykhuizen 2004, the authors clearly differentiate the two as separate forces. NFDS resulting in rare strains of the Lyme pathogen having an advantage, but all alleles having equal probability in all host types. In MNP, strains are partitioned by host type.
That all seemed to make sense to me, but then I read this webpage stating that MNP is just a type of NFDS. I can't seem to find much other info on MNP, so I'm a bit confused. It seems like NFDS would promote genetic diversity in a mixing population while MNP would result in fixed differences between host types and a divergence in populations. Am I incorrect? Is MNP just a subset of NFDS?
I'm looking to create a method where I can generate a sample of events. Each event has an associated energy, with higher energy events being less frequent. If I consider a single narrow bin of energy, there would be an average of N events of this energy bin in one unit of time, with the likelihood of each event occurring being independent of any other event. So, for this one energy bin, I could generate a sample of events based on the Poisson distribution. However, I want a sample of events across a range of energies. There is a linear relation between the log of the event frequency and the log of the event energies (with a decrease in energy related to a decrease in frequency). I would like to be able to generate a sample of events for a given time interval over a specific energy range (say, for the range of energies from 10^0 to 10^10). For my practical use case, splitting that range of energies into bins, then sampling for each bin based on the Poisson distribution would probably be sufficient. However, I'm certain there must be a more direct/analytical solution. As I can make these sampling bins arbitrarily small, when taken to the limit, I think this should become some form of integration problem. However, it's not clear to me how to use this to build a method that can generate a sample of events. Any suggestions on how to proceed? Thank you much!
I read somewhere that AM is bad because it is prone to interference from wide variety of things, switches, electric motors, bulbs, etc.
I'm trying to build an EM shielded enclosure with 1mm hole size aluminum mesh, earlier prototype I built was able to get cell phone signals and FM radio inside the enclosure, but I didn't check AM at that time, do you think even an enclosure with few disconnections here and there and few holes larger than 1mm be able to attenuate AM at any frequency? Not just commercial AM radio but amplitude modulated signal at any frequency.
https://forms.gle/Q894yTG3xnZNh4VH8
This survey is for our graduation project where we are developing a recipe-sharing and collaboration application. We want to determine which features of the application are more important. The survey is mostly multiple-choice and all questions are optional to answer. If you have any questions or ideas about the project please feel free to contact me :)
Thanks in advance!
I am curious, and have been for some time, how devices like radio receivers seem to pick out one specific frequency at a very narrow bandwidth and attenuate all others. Of course there is filtering, and I have done a little work designing a band pass filter, but I find that for sufficient performance like I am seeing in very small electronics I would need a very large order filter to attenuate as quickly as I expect these devices do. And from my limited design experience I find that designing high order band pass filters is time consuming, requires a lot of board real estate, and is prone to errors with passive tolerances.
So my question is, how do cheap radio receivers, do such a fine job selecting a single frequency, while maintaining a small package. I’m also wondering how some devices can select different frequencies (like a walkie-talkies) are they using different filtering circuits or is there some overlap?
Energy for all waves I can think of depend on the square of amplitude but with photons it only depends on frequency. Is it because every photon has the same amplitude and 'adding aptitude' is akin to superimposing multiple photons onto of each other?
