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Questions tagged [biophysics]

The use of methods from the physical sciences to aid in the study of biological systems. Note that biophysics questions are only allowed if they are mainly about physics.

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Tendon excursion method application/alternative for joint represented by quaternion in biomechanics

I am building a biomechanical model that consists of spherical joints. I wanted to represent these spherical joints by quaternions. I am struggling to derive how the muscles contribute to the ...
blenderman's user avatar
3 votes
2 answers
39 views

How do I compute the voltage accross a cell membrane given microstate of neuron (distribution of charged ions)?

I am not a physicist, and I'm not sure what keywords to use to search for this. I'm trying to understand how I could in theory quantitatively know, what the voltage across a cell membrane in a Neuron ...
user56834's user avatar
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15 votes
2 answers
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Eye Floaters Optics

Eye floaters are these annoying objects floating in someones eye, usually seen by someone experiencing them as squiggly lines and dots buzzing around, either dark or partially transparent (I ...
TomY's user avatar
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5 votes
3 answers
371 views

Why do most fish wiggle their tails side to side, and not up-down?

Is moving a vertical fin side to side more efficient than moving a horizontal fin up and down in water for fish locomotion? The answer might lie in how fish propel themselves using vortices, but I don'...
AlphaLife's user avatar
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1 vote
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Resources on Phase Ordering Dynamics and Non-Linear System

I am doing a course on Non-Equilibrium Physics. Prof. was initially following Strogatz but has now started teaching Phase ordering dynamics, Cahn-Hillard equation and all? I can't seem to find a good ...
4 votes
2 answers
106 views

What does life (photosynthesis) change for entropy? A thought experiment

The relationship between entropy and life is complex and has even "philosophical" ramifications. The following thought experiment seems simple enough to bring a clear answer, but I'm unsure ...
YAG's user avatar
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-3 votes
1 answer
110 views

Does quantum tunnelling have anything to with perception of light?

There have been studies suggesting that the sense of smell has something to do with quantum tunnelling but I'm afraid I don't know the exact details. Do we possess internal mechanisms that simply &...
DanielFBest's user avatar
3 votes
1 answer
94 views

Bicycle Uphill vs. Walking Uphill

When bicycling uphill, I have noticed it takes a enormous amount of effort compared to just walking uphill. However, when on level ground, bicycling seems to take considerably less effort than walking....
dtz's user avatar
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1 answer
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Calculating jumping distance?

I'm trying to figure out how to calculate the jumping distance of a person or animal based on body weight and initial speed, but I can't seem to find any relevant information online about this. Is ...
Papa Solen'ya's user avatar
2 votes
1 answer
54 views

Is it possible to calculate the weight distribution on each foot from the centre of mass of a human body?

I want to know if it’s at all possible to calculate the weight distribution (i.e the relative load supported by each foot) using just the location of the human body’s centre of mass and the distance ...
Reiho's user avatar
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Average resultant length $L$ of an active string initially of length $L_\mathrm{0}$ after a single point mutation

I stumbled upon this research article, where they define a digital organism as an abstract minimal model of an evolving predator-prey system as follows: An organism is defined via its genome of fixed ...
lahamirad's user avatar
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Effects of chromatic aberration in the human eye

Due to metamerism, many different light spectra can be used to show a white colour. If I understand it correctly, it is even possible to make white light by combining only two monochromatic light ...
user13062187's user avatar
2 votes
1 answer
81 views

Could a geomagnetic storm disrupt the functioning of nerves?

It is known that geomagnetic storms can cause power grid outages. Can they also disrupt the functioning of nerves/the nervous system?
Malcom's user avatar
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1 vote
0 answers
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What was Grant Holloways top speed in his 12.81s 110m hurdle run using kinematics? [closed]

I am a currently a introductory biophysics student and I am attempting to analyze Grant Holloway's 12.81s 110m hurdle run. I thought the best approach would be to break the run into stages due to the ...
Dalyn Coffey's user avatar
3 votes
2 answers
250 views

If we have a beam of photons and a beam of protons with the same energy, which one will get further inside the human body?

If we have a beam of photons (high energy X-ray) and a beam of protons both with the same energy, which one will get further inside the human body and why? Can this be explaind due to LET (Linear ...
Reza Mullaj's user avatar
2 votes
2 answers
89 views

Why does Near Infrared (NIR) light allow deeper imaging in biological tissue in Multiphoton Microscopy?

I have been reading this paper on multiphoton microscopy (https://www.nature.com/articles/nphoton.an.2010.2) and I am very confused about something. Here is a quote from the paper: "The NIR ...
Sigma123's user avatar
1 vote
0 answers
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Question regarding notation

In the paper Inverse statistical problems: from the inverse Ising problem to data science for equation (51), the authors state, "This yields equations which determine the values $m^{MF}_i$ of the ...
Pugs's user avatar
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2 votes
1 answer
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Understanding the transfer matrix for a 1D Ising Model

I apologize in advanced for how trivial this question will come to many of you. I am in fact not a Mathematician nor physicist, just a math friendly Biologist who needs to understand the transfer ...
Nick's user avatar
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0 answers
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What is the relation between the torque generated by the flagellar motor and the torque acted on the flagellar and cell body?

I was reading a lecture slide on modeling the motion of E. Coli and came into this set of equations. The equations are given assuming the bacterium is in constant straight motion so no net force and ...
Winniebear's user avatar
1 vote
2 answers
155 views

Mean squared displacement of a particle on a biased random walk [closed]

Given a particle on a 1-D random walk with some drift velocity $\nu_d = \frac{\Delta x_d}{\Delta t}$, the position in at some time step j is given by $$x_j=x_{j-1}+k_j L + \Delta x_d$$ where $L$ is ...
mertvy's user avatar
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3 votes
2 answers
129 views

Why are systems operating far from equilibrium more efficient?

In many (biological and living systems) physics courses I encountered the notion that systems operating far from equilibrium are related with more efficiency with regard to their specific tasks. One ...
YoussefMabrouk's user avatar
8 votes
2 answers
187 views

Back-of-the-envelope estimate of thermodynamic cost of food absorbtion from first principles

Just out of curiosity, I'm trying to get a sense of the order-of-magnitude theoretical thermodynamic cost of food absorbtion. I'm thinking of food absorption as "move nutrients in newly consumed ...
user56834's user avatar
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0 votes
1 answer
39 views

Do vibrational frequencies produced from sound pass through your entire body? from one side to another? [closed]

when there is a noise by me, i feel the vibration on my skin from the direction it’s coming, it moves into my body. a wall of what sound would feel like passing through me. i perceive it as container ...
na.arah's user avatar
3 votes
3 answers
653 views

How can infrared light interact with nerve cells given the wavelength is so much longer than the cell's size?

I obviously do not understand how a wavelength greater in length than a cell can be detected by a cell. As I understand it, infrared ranges from 300GHz to hundreds of THz. As an example, if an ...
Gary La's user avatar
  • 31
1 vote
0 answers
74 views

Biophysics intro resource recommendation for a math stat PhD

(Question has been edited for specificity based on feedback. I followed the guidelines StackExchange recommended to me: Are resource recommendations allowed?) Within biophysics, I'm looking to build ...
16 votes
9 answers
5k views

Why does an MRI machine or other EMP generating machine not damage humans, but it will fry computers?

A sufficiently strong electromagnetic pulse can/will destroy smartphones and computers. I know somebody who went into MRI machine and forgot a Visa credit card in his pocket. The card was toast and he ...
ShoulO's user avatar
  • 289
1 vote
1 answer
1k views

What takes more energy? Walking up stairs or ramp over the same height?

Often when we go hiking, we encounter two kinds of paths whenever we have to cover elevation. We either go up via stairs or via walking up a ramp. Sometimes both are available side to side. And it's ...
Paagalpan's user avatar
  • 111
1 vote
0 answers
37 views

Functionalizing iron oxide nanoparticles for antimicrobial activity [closed]

I'm working on my thesis which is about synthesis of iron oxide nanoparticles from a plant leaf extract and testing the particles activity on bacteria to measure their toxicity towards it. The thing ...
just asking's user avatar
1 vote
1 answer
369 views

Why is water bright in a T2 weighted image?

I am new to study MRI. Please understand if some terminologies I use are wrong. This might be a silly question, but I wonder why water is bright in a T2 weighted image. T2 relaxation is also called ...
Andy Junghyun Kim's user avatar
3 votes
1 answer
55 views

Why does vitrification cause less damage to biological tissue than freezing does?

Long-duration cryopreservation of biological tissue (most often semen, egg cells, or fertilized embryos) is typically done at 77 K, since the samples can be easily kept at that temperature by ...
tparker's user avatar
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0 votes
1 answer
68 views

How does safe fall distance scale with the size of an animal?

An animal has a maximum safe fall distance, the distance it can fall without getting hurt. If you take an animal and a similar animal twice as large, what would we expect to hold about the maximum ...
causative's user avatar
  • 820
0 votes
1 answer
272 views

Why does a centrifuge cause blood to be pushed downwards in the human body?

Good evening all, I recently watched this YouTube video about a centrifuge by Tom Scott (https://www.youtube.com/watch?v=DMKcO-T5Y4o). Around the 2:30 mark, it is said that blood will be 'pushed ...
Thomas's user avatar
  • 81
2 votes
2 answers
2k views

Why does UV light feel warm on my skin? Whereas infrared light heats up space around me plus my skin?

Noticed something weird today. I have an infrared space heater that is pretty good at heating up my desk at work (as well as my skin obviously). I also have a UV flashlight. I noticed the UV ...
user3807846's user avatar
-2 votes
1 answer
226 views

What would a hypothetical lifeform in a universe with no electromagnetism look like? [closed]

I was watching an amazing Arvin Ash video in which he explained the purpose of light and speculated that life could possibly exist if the universe did not have the electromagnetic force but just ...
Max's user avatar
  • 1
5 votes
2 answers
320 views

Quantitatively, how much would radiation levels increase without the geomagnetic field?

Many, many popular science articles claim that if the Earth didn't have a magnetic field, then the much higher concentration of cosmic rays that reached the surface would cause health damage to humans....
tparker's user avatar
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4 votes
1 answer
305 views

What causes blood flow to become turbulent after a constriction?

If a blood vessel is narrowed from the middle, the blood flow turns turbulent (see image below). Why does this happen? Does it have to do with Reynolds number becoming high because velocity has ...
Cosmic Dust's user avatar
1 vote
0 answers
27 views

What Continued Upwards Momentum Has to Do with Vortex in Bee Wings?

In this answer to how bumblebees fly, it says that The wing motion has a sort of double lift feature. By twisting her wings over at the end of each down stroke, the upward momentum is never lost. ...
MeltedStatementRecognizing's user avatar
3 votes
1 answer
385 views

Under what conditions is mean square displacement $\text{MSD}(t)=4Dt+v^2t^2$ a valid asymmetric random walk model?

I am reading the paper Actin dynamics drive microvillar motility and clustering during brush border assembly by Meenderink et al. (2019). In this paper, the authors fit the mean square displacement (...
BioPhysicist's user avatar
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0 votes
0 answers
43 views

Why is it important to release energy as quickly as possible to perform a vertical jump?

Let's assume that we create this mechanism, where we must decide if the actuating cylinders are double-acting hydraulic or pneumatic with a spring inside. the goal is for the mechanism to suddenly ...
Matias Nicolas Rodriguez's user avatar
1 vote
0 answers
32 views

Choice and Energy [closed]

Does the action of making a choice expend energy? If any conscious choice is predetermined, it must always be taken towards a greater entropy state, which means it must somehow "know" ahead ...
Lex Podgorny's user avatar
10 votes
2 answers
2k views

Where do beta particles go after being emitted from the nucleus?

What high-school taught me: In beta radiation, beta particles are lone electrons that are emitted from the nucleus at high speeds after a neutron decays into a proton and an electron. Beta radiation ...
user avatar
0 votes
1 answer
30 views

Can you perfectly control electric currents' behavior in anisotropic media?

I'm an undergrad who is learning recently about anisotropy w.r.t. E&M. I understand that in anisotropic media the behavior of electric currents and other E&M aspects can be very unpredictable ...
φρέᾱρ's user avatar
1 vote
1 answer
70 views

Electronic tunneling between two states

I am reading Steering Electrons on Moving Pathways (Beratan et al. 2009) which is about electron tunneling in biomolecules, and specifically the processes via which an electron can move from an ...
slithy_tove's user avatar
3 votes
0 answers
62 views

How often does a molecular machine run in reverse?

I was reading the Wikipedia article on Stochastic thermodynamics, and came across this statement in the overview: When a microscopic machine (e.g. a MEM) performs useful work it generates heat and ...
nullspace's user avatar
1 vote
1 answer
90 views

What is the hydrodynamic interaction (Oseen kernel)?

I am reading through the paper "Dynamics of Membranes Driven by Actin Polymerization" by Nir S. Gov and Ajay Gopinathan. In this paper, the authors develop a PDE model to explore the ...
BioPhysicist's user avatar
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2 votes
0 answers
60 views

Is a worm-like-chain purely entropic?

I consider a worm-like chain with the Hamiltonian given by: \begin{equation} H(L)=\frac{\kappa}{2}\int_{0}^{L}ds\left(\frac{\partial\vec{t}}{\partial s}\right)^2 \end{equation} where $\kappa$ is the ...
Paweł Korzeb's user avatar
1 vote
0 answers
32 views

Elucidation needed in protein dynamics

I'm reading some papers about protein dynamic, stability and energy landscape. Switching from paper to paper I'm encountering different term used for talking about protein movements, for example: α- ...
2 votes
1 answer
200 views

In an open quantum system, what is the justification for using a harmonic oscillator bath to represent the molecular environment in a solvent?

The Caldeira-leggett (CL) model is sometimes used to describe quantum mechanical effects in a system (like a biomolecule) immersed in a solvent. The Hamiltonian of the CL model consists of an ...
Prem's user avatar
  • 2,326
1 vote
1 answer
161 views

How to understand radiation dose and dose-area-product?

I am learning about radiation protection measures and am confused about the idea behind certain measures and practices, and I hope somebody can help me. Dose definition and Gy The absorbed dose is ...
BrknKybrd's user avatar
1 vote
0 answers
88 views

Radical pair mechanism in photosynthesis

I am aware that in Photosystem II of the chloroplast, there sometimes forms a spin-correlated radical pair of electrons whose spins precess around the effective magnetic field for several nanoseconds (...
slithy_tove's user avatar

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