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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Modeling the Effect of Magnetic Induction on Single Neurons

In this paper, the authors suggest a potential mechanism for magnetoreception in birds: as the Earth's magnetic field (taken to be homogeneous over sufficiently small spatial scales) passes through ...
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2 answers
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Why don't we overheat just by existing? What is the theoretical model? [closed]

Our bodies constantly generate heat, but we don't overheat just by sitting in room temperature! Why? Something about the shape of our bodies at standard-temperature-pressure is at equilibrium with the ...
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2 answers
201 views

Do photosynthesis and respiration violate the law of conservation of energy?

I don't know, if it's a physics question, biology or chemistry question but anyways here it is: I have been taught that for making one molecule of glucose in photosynthesis 18 ATP molecules are used ...
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How does an electrode (e.g., an ECG lead) measure biopotential changes?

In many medical procedures, electrodes are used to measure various physiologic biopotentials. The most common example is that of an ECG procedure, in which electrodes attempt to sense changes in ...
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How can you get the isotropic Young's modulus and Poisson's ratio from rheology data?

I wanted to ask on how to get the Young's modulus and Poisson's ratio for a viscoelastic biomaterial. I have rheological data from the characterization of the biomaterial, the G' and G'' (storage and ...
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Analytic solution to geometric swinging problem

I came across this problem in the context of developing a game about a brachiating gibbon, swinging from handhold to handhold. (for context.) I was looking for a way to calculate what the gibbon's ...
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Transmural pressure versus Perfusion Pressure (driving pressure)

I learnt about 2 types of pressure gradients that needs to be considered in the cardio-vasculature. Transmural pressure (which refers to a pressure gradient felt across the vascular wall, at one ...
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Iridescent duck and photonics in nature. Why duck's head is only green?

We all know and adore pure beauty of mallard male: I know that such iridescent colours are usually a result of feathers forming a photonic crystal with layers of air sandwiched between layers of ...
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What are some good resources to study Biophysics for an undergraduate level?

I am studying Biophysics as a part of my Biotechnology bachelor program. I want to study the subject as best as I could, from a beginner level to graduate level. Please, recommend textbooks, online ...
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What does it mean for sunlight to be of low entropy?

I once listened to a lecture by Sir Roger Penrose on life and also read the second answer to this question. If I understood correctly, then the reason why life still exists on earth inspite of the ...
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Can nanotechnology build a virus? [closed]

I heard that nanotechnology can arrange atoms the way one wishes. The atomic force microscope can control the arrangement. As the composition of the viruses is known, can by nanoprinting a virus be ...
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Production of Nitrogen Vacancy Centers

A Nitrogen Vacancy Center is a diamond defect in which a carbon atom is replaced by a Nitrogen and the adjacent carbon atom is replaced by a "vacancy", hence the term Nitrogen Vacancy (NV). ...
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How far can the human eye see? [duplicate]

This question has already been asked but the answers are old and the links no longer work. I'm interested in the answer but even more in research papers that have shown the answer.
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1 answer
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How do migratory birds fly in geodesics? [closed]

Recent studies point to cytochrome molecules in the eyes of migratory birds as a key component for birds to use when flying across the globe. It is thought they help the birds navigate using the earth’...
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2 answers
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Is the human singing voice different from a linear, time-invariant (LTI) system?

Typically the human voice is modelled by a linear, time-invariant (LTI) system. An LTI system cannot add any frequency components to an input signal. This is obvious from the input-output relation in ...
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1 answer
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Formal definition of Wall Shear Stress (WSS)

I am looking for the formal definition of the scalar wall shear stress for an arbitrary fluid in 3D. Here, I hope to find a definition that allows both positive and negative scalar values. My ...
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1 answer
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Free energy landscape and probability distributions

I couldn't understand the concept of free energy landscape. Usually free energy is defined in the following way. $$F=-k_{B}T\ln Z=-k_{B}T\ln\sum e^{-\beta \epsilon}$$ where $\epsilon=\sum\frac{p_{i}^{...
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Why do Blue Morpho butterflies appear blue?

Blue Morpho butterflies are said to display structural coloration, but how do their scales cause light to diffract in such a way that they appear blue? I just don't understand how it's blue light that ...
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14 votes
6 answers
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Are neurons more energy efficient than transistors?

In terms of order of magnitude, how does a the energy consumption of a typical mammalian neuron (in the brain) compare with the state of the art MOSFET?
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Current flow because of a point source

Do I understand this sketch correctly, that the technical direction of flow is drawn here? In case of a cathodic pulse from the point source, the physical direction of the current would point away ...
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1 answer
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Can deterministic and stochastic models be used to models different parts of the same phenomenon?

A biological phenomenon including two different causally dependent phenomenon occurs in the cell. (Phenomenon2 initiates as a result of phenomenon1). Phenomenon1 and phenomenon2 are linked with ...
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2 votes
4 answers
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Why do we get a shock from electric wire instantly? [duplicate]

As we know the drift velocity of electrons in conductors is very low and it is about a few millimetres per second. Now suppose I hold one end(naked) of a wire which is not connected to any source. ...
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1 vote
1 answer
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Why Does this Expression for a Probability Have Units?

In this paper titled "Measurement of Photon Statistics with Live Photoreceptor Cells" the equation 3 which expresses a relation for the probability of a given photocurrent given a certain ...
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Influence of the current polarity in the Hodgkin-Huxley model

Suppose I place a monopolar electrode at a certain distance from a target neuron, which can be described by an electrical circuit according to the HH model (see picture). Why is there such a ...
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-1 votes
1 answer
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Question about potential additives to a very relative Covid 19 m R N A patent (i.e. radio active Ions: Iodine 125 or 131, Strontium 89, cesium, etc.) [closed]

I am a genuinely concerned citizen with barely any scientific background concerning radioactive isotopes. However, I have a question about items listed in an mRNA 1273 patent on Moderna's website. ...
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2 votes
1 answer
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Is it okay to sleep with the wifi router next to me?

Where I sleep I have my wifi router right above me. I don't know if this is safe for my health since it emits radiation. Some people say that it should be safe since the radiation emitted is non-...
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3 votes
1 answer
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For weighted pull ups, how does positioning the weight below the hips (eg a dip belt) make the motion harder than when placed on the back (eg a bag)?)

I have been doing pull-ups for a while and decided to recently transition into weighted pull-ups for more growth. When gathering advice, I discovered that placing a weight between the legs, with the ...
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9 votes
3 answers
2k views

Local decrease of entropy, does it require life?

Universal entropy can decrease only locally at the expense of bigger increase elsewhere. Can this occur in a lifeless environment or does it necessarily require living organisms to do it? Can this ...
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2 answers
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Is the human body more than perfectly efficient? [closed]

The average person weighs about $700\,\text N$. If they run $5,000\,\text m$, the formula for work says they do $700\,\text N \cdot 5,000\,\text m = 3.5\,\text{MJ}$ of work, or $836.5\,\text{kCal}$ of ...
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What frequency if radiated during neuronal depolarization?

In accordance to the Larmor formula in electrodynamics, any change in the velocity in a electric charge will result in the emission on electromagnetic radiation. What frequencyis radiated while a ...
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0 votes
1 answer
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What laws of physics suggest life and evolution will occur? [closed]

Do any laws of physics tell us why life and evolution occurs? From my understanding the laws of physics is about reduction/materialism and with that we can explain everything else. To that end, which ...
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11 answers
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Why does running spend more energy than walking?

The study energy expenditure of walking and running concludes that running spends more energy than walking. My understanding is that although running makes one feel more tired, that only indicates ...
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0 answers
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Book recommendation for hydrodynamics of bubbles, drops, and particles

I am wondering if someone could please recommend to me some references on the topic of hydrodynamics of bubbles, drops, and particles, preferably in the context of complex and bio fluids. I am ...
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Efficiency formula in Environment-assisted quantum transport (ENAQT)

I'm currently studying the book quantum effects in biology, in particular, I'm interested in the phenomena of Environment-assisted quantum transport (ENAQT) in photosynthesis. In ENAQT, they discuss ...
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3 answers
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How come light in the Violet spectrum looks like a mixture of Red and Blue, even though they are of different wavelength? [duplicate]

How come pure monocromatic light in the violet spectrum is perceived by us as light that is a superposition of 2 other, different wavelength light. is there some scattering process in the eye that ...
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1 answer
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Does brain activity generate anything outside our bodies? [closed]

I have been reading recently about the Law of Attraction and while I don't believe in its 'scientifical' basis it did make me think about whether our brain produces any kind of activity strictly ...
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1 answer
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Why was RGB chosen as the basis / primary color set for pixels?

Human eyes have retinal cells that are sensitive to red, green, and blue light. Pixels on electronic screens use the same three colors to produce many apparent colors. But a little thought (and ...
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How to derive the Potts model as well as the gauge transformation *directly* from the principle of maximum entropy?

$ \newcommand{\delim}[3]{\left#1#3\right#2} \newcommand{\delimzero}[3]{#1#3#2} \newcommand{\delimone}[3]{\bigl#1#3\bigr#2} \newcommand{\delimtwo}[3]{\Bigl#1#3\Bigr#2} \newcommand{\delimthree}[3]{\...
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2 answers
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Atom or Cell? Which is the basic unit of life? [closed]

As it is said that everything in this universe is made up of atoms and molecules and atoms are called the building blocks of matter. But then why the cell is called the basic unit of life, why not ...
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0 votes
2 answers
54 views

What scientific evidence is there for the definable real world quality of redness independent our perception? [closed]

With light poise and counter-poise, Nature oscillates within prescribed limits. Yet thus all arise the varieties and conditions of the phenomena which are present to us in space and time. - Goethe ...
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Photosynthesis relation to work function and photoionization

When photosynthetic organism’s use pigments such as chlorophyll, the metal ion in the center emits an electron after absorbing a specific wavelength of light, at 400-700 nm This does not make sense to ...
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1 vote
1 answer
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Are there physical reasons for breaking this symmetry in biological systems?

For some reasons, it seems that particular "handedness" are chosen by nature, because we have the prevalence of some enantiomer, that have different optical properties respect to ...
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2 answers
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Did we adapt to Earth or Earth to us? [closed]

I often hear that Earth is a unique planet because it has life and it has its own inhabitance. We also see a proper balance between plants and humans and other animals. Why life is not possible on ...
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2 votes
1 answer
57 views

Can a Cochlear implant impart superhuman hearing? [closed]

The bandwidth of human hearing determined by empirical data is $20 \; Hz$ to $20 \; kHz$. A cochlear implant stimulates the auditory or acoustic or Cochlear nerve directly so that the hearing can be ...
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What are the technological limitations of DNA computing? [closed]

IBM and Microsoft are studying the application of DNA computing, but I was wondering what are the technological limitations that prevent it from being used in the same way as a conventional digital ...
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Does physics allow for many competing biologies or only one biology? [closed]

Does physics allow for many competing biologies or only one biology? I read sci-books about life based on silicon and I've read an article that said that other structure than DNA can encode genetic ...
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38 votes
12 answers
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Does physics explain why the laws and behaviors observed in biology are as they are?

Does physics explain why the laws and behaviors observed in biology are as they are? I feel like biology and physics are completely separate and although physics determine what's possible in biology, ...
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-1 votes
4 answers
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Calculating work done or energy expended difference in two biomechanics examples [duplicate]

I have a biomechanics question regarding how much work is done (or energy consumed) by a person moving at a constant speed from point $A$ to $B$. In the first scenario, $A$ to $B$ is $100 \; \text{m}$...
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2 votes
1 answer
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Upconversion Particles in Biological Tissues

So I was learning about upconversion particles in biological tissues and understand mainly how they work. UV-Vis light are scattered and absorbed by tissues, so we instead send near-infrared light to ...
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Discriminate closed-chain from open-chain

I have two classes of chains: closed-chains where a random path ends near where it starts (ie. loop), and open-chains without this restriction (ie. random walk). These chains are a directed graph ...
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