Archive for the ‘BIOLOGY’ Category

Nonequilibrium Physics in Biology

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Xiaona Fang, Karsten Kruse, Ting Lu, Jin Wang
Life is characterized by a myriad of complex dynamic processes allowing organisms to grow, reproduce, and evolve. Physical approaches for describing systems out of thermodynamic equilibrium have been increasingly applied to living systems, which often exhibit phenomena unknown from those traditionally studied in physics. Spectacular advances in experimentation during the last decade or two, for example, in microscopy, single cell dynamics, in the reconstruction of sub- and multicellular systems outside of living organisms, or in high throughput data acquisition have yielded an unprecedented wealth of data about cell dynamics, genetic regulation, and organismal development. These data have motivated the development and refinement of concepts and tools to dissect the physical mechanisms underlying biological processes. Notably, the landscape and flux theory as well as active hydrodynamic gel theory have proven very useful in this endeavour. Together with concepts and tools developed in other areas of nonequilibrium physics, significant progresses have been made in unraveling the principles underlying efficient energy transport in photosynthesis, cellular regulatory networks, cellular movements and organization, embryonic development and cancer, neural network dynamics, population dynamics and ecology, as well as ageing, immune responses and evolution. Here, we review recent advances in nonequilibrium physics and survey their application to biological systems. We expect many of these results to be important cornerstones as the field continues to build our understanding of life.

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Written by physicsgg

December 10, 2020 at 12:15 pm

It’s Still Not Too Late To Fight COVID-19 Like A Scientist

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1.) We need a national mask mandate. Sorry to all those with a medical reason why you can’t wear a mask; the fact of the matter is that the risks of both transmitting and acquiring the novel coronavirus skyrocket without a mask. While N95 and surgical masks are (and should be) reserved for hospital settings, both hybrid masks and two-layer cotton masks offer outstanding protection in three vital ways:

  • they efficiently filter large droplets,
  • they efficiently filter aerosols,
  • and they effectively reduce the distance your droplets and aerosols travel, protecting others.

While masks, scarves, bandanas and gaiters all vary in quality and effectiveness, any face covering is significantly better than no face covering.

Face shields, though a popular alternative, offer little-to-no protection to the wearer compared to masks.

Contrariwise, masks with built-in valves or vent protect the wearer, but do not protect others. As a rule of thumb, if you cannot blow out a candle while wearing your covering, it’s likely to be effective. Those who wear masks are not only far less likely to infect others, but their COVID-19 infections are much more statistically likely to be mild, rather than serious or worse.

2.) Remain socially distant, and have it enforced. When you leave your house, or come into contact with anyone who doesn’t directly live with you in your household, you should keep a minimum of 6 feet (~2 meters) away from every other person. What constitutes 6 feet?

  • The width of a passenger car.
  • The length of two typical shopping carts.
  • Or if two people both held their arms out fully extended, leave approximately a full foot (30 cm) gap between your mutual fingertips.

The reason is simple: the virus is spread by airborne particles that are expelled by respiratory activity. This includes breathing, laughing, singing, talking, shouting, playing musical instruments, coughing, and sneezing, among others. With an effective mask, the viral load launched into the air can be greatly reduced, as can the distance that droplets and aerosols travel. Without a mask, they can easily travel up to 26+ feet. A recent meta-study found that not only were 6 foot (2 meter) distances effective in reducing viral transmission, but that every additional 3 feet (1 meter) reduced transmission and susceptibility even further. Speaking up when someone’s standing too close should be normalized, and leaving enough distance between people for safety’s sake should be mandatory.

3.) Do not gather indoors with people who live outside your household. The top determinant in whether someone catching the novel coronavirus SARS-CoV-2 is as straightforward as it gets: exposure. The greater your exposure, the greater your odds of catching COVID-19, and the greater your exposure, the greater the likelihood you’ll have a serious, severe, or even deadly case of it.

When you’re indoors, aerosol particles remain in the air and — if anyone who’s been in that space is infected with SARS-CoV-2 — continue to increase the viral load a person in that space is exposed to. Spaces where eating or drinking occurs (like bars or restaurants), where singing or raised-voice speaking is common (like classrooms or churches), or where strained, heavy breathing occurs (like gyms) only exacerbate this effect.

If we cared about taking public health precautions seriously and reducing infection rates, there would be a moratorium on gathering in-person in spaces such as this until the virus was under control. While the virus isn’t under control right now in the United States, there’s a remarkably simple way to get there.

4.) Enforce a 4-to-6 week “stay at home” plan. This is the enormous step that could lead us to victory over the virus, but that requires national coordination and enormous levels of societal compliance to be successful. The reason the virus has continued to spread throughout the population over the past six months — and will continue to do so as long as the current conditions do not change substantially — is that far too many of us are engaging in non-essential contacts far too frequently.

We can combat that by having a nationwide shelter-in-place order. We can prepare for this by:

  • setting up infrastructure to provide essentials (like food and medicine) delivered or picked-up without person-to-person contact,
  • paying all Americans to stay home and not (need to) work during that time,
  • and to enforce fines and other punishments for those who violate the order.

The few essential contacts that cannot be eliminated (mostly for healthcare reasons) will ensure that some amount of virus will remain in our population, but shelter-in-place (i.e., stay-at-home) orders are one of the most successful public health interventions a society can take to combat a pandemic such as COVID-19.

5.) Reopen according to science-based guidelines. Even though we’ve been combating the novel coronavirus in the United States for 6 months, we still aren’t following the recommendations of scientists. We don’t have universal contact tracing. We don’t have rapid, widespread, mass testing. Because we don’t know who’s positive and who’s been exposed, we aren’t isolating or quarantining appropriately. That means that asymptomatic carriers, presymptomatic carriers, and people who have active, symptomatic infections are all out in public, with the potential to infect each and every one of us.

If we cared about stopping this pandemic and preventing hundreds of thousands of further deaths, we would engage in all three of these interventions:

  • universal contact tracing,
  • widespread, rapid, mass testing,
  • and science-based isolation and quarantine practices for the infected and exposed.

Where infections start to rise, a local stay-at-home order could squash an outbreak with this information before it spreads to other communities.

A network epidemiology map of the connections between a set of households if only essential connections are allowed to occur. Note both the large number of isolated households that do not have connections with any other households, and the relatively small size of the largest connected network. GOODREAU SM ET AL., ON BEHALF OF THE STATNET DEVELOPMENT TEAM (2020)

These five interventions, taken together, could in principle take us from tens of thousands of new cases per day to merely hundreds in just a few weeks. Just as many countries with large populations and widely varying population densities have already safely reopened by taking exactly these steps, recovering from catastrophically large initial infection rates, the United States (and the United Kingdom, and other countries with similar circumstances) could completely turn the tide in the fight against COVID-19. It simply requires following the best scientific advice that the experts have to offer.

Without it, the disease will continue to ravage individuals, families, communities and the nation as a whole. The economic impacts will be severe and drawn-out, and our best hope of defeating it will come from a vaccine. Even then, we have to be scientifically responsible on that front, too: vaccines need to be proven safe and effective, and realistically not a single one is close to the finish line yet. A rushed vaccine not only might not work — giving people false hopes of protection — it could have unacceptably dangerous side effects.

The best part about this science-based solution is that it’s always available to us: we can choose to adopt it at any time. The social and economic impacts of the pandemic continue to be disastrous, but they can be remedied by making the conditions safe for everyone: workers, customers, teachers, and students. By enforcing mask mandates, distancing requirements, moratoriums on risky activities and businesses, a 4-to-6 week coordinated shelter-in-place order, and only reopen with science-based guidelines in place (that include contact tracing, widespread testing, and isolation/quarantines for the infected and exposed), we can beat the virus as a society.

Many of us, understandably, are beyond fatigued at the impact that the novel coronavirus has had on our lives. The idea of having to isolate ourselves further is truly frightening, but it’s an action that can have a greater impact on stopping this virus in its tracks than anything we’ve done to date. Until a safe and effective vaccine is widely available, this is the scientific path to a safely reopened America. We can choose it at any time. The sooner we do, the more lives we’ll have saved.

Written by physicsgg

September 10, 2020 at 8:18 am

Posted in BIOLOGY

Effects of exoplanetary gravity on human locomotor ability

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Nikola Poljak, Dora Klindzic, Mateo Kruljac
At some point in the future, if mankind hopes to settle planets outside the Solar System, it will be crucial to determine the range of planetary conditions under which human beings could survive and function. In this article, we apply physical considerations to future exoplanetary biology to determine the limitations which gravity imposes on several systems governing the human body. Initially, we examine the ultimate limits at which the human skeleton breaks and muscles become unable to lift the body from the ground. We also produce a new model for the energetic expenditure of walking, by modelling the leg as an inverted pendulum. Both approaches conclude that, with rigorous training, humans could perform normal locomotion at gravity no higher than 4 gEarth.

Written by physicsgg

August 23, 2018 at 5:36 pm


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Toward a Neurobiological Basis for Understanding Learning in University Modeling Instruction Physics Courses

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Written by physicsgg

May 29, 2018 at 1:42 pm


The laws of life

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Perhaps the questions were too speculative for his time, but Charles Darwin never considered whether another evolutionary experiment exists in the universe or what such an experiment might look like. Once life emerged on Earth, it proliferated across the planet, assumed remarkable forms, and wrought the extraordinary changes that have now inextricably linked the biosphere and geosphere. The oxygen that you and I breathe originated as the result of photosynthetic activity so pervasive and so productive that it eventually reached levels sufficient to drive a complex multicellular biosphere…

Written by physicsgg

March 4, 2017 at 9:13 am

Posted in BIOLOGY

How Does Life Come From Randomness?

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Written by physicsgg

July 1, 2016 at 7:09 pm

Posted in BIOLOGY, Thermodynamics

A Penny For Your Thoughts

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How much is your time really worth? Student paper evaluates the economics of thought

Big thinkers may wish to re-evaluate their rates, according to a student study at the University of Leicester, which tested the popular idiom ‘A penny for your thoughts’ by working out how much of a person’s thought could theoretically be purchased with a single penny.

The study suggests that a penny could, in theory, purchase 3 hours, 7 minutes and 30 seconds of thought according to Natural Sciences student Osarenkhoe Uwuigbe from the University of Leicester’s Centre for Interdisciplinary Science.
In a paper published in the Journal of Interdisciplinary Science Topics, a peer-reviewed student journal run by the University of Leicester’s Centre for Interdisciplinary Science, the student first investigated how much power is needed to produce thought.
For simplicity, the study examined the power necessary for the brain – which consumes roughly 20 per cent of the body’s energy – to run as being the power necessary for the production of thought.
Given that the average power consumption of a typical adult is approximately 100 watts, the student calculated that the power necessary to run a human brain and produce thought is roughly 20 per cent of this – or 20 watts.
To apply monetary value to thought, the price per kilowatt hour (kWh) charged by UK energy companies was calculated, settling on 16 pence per kWh, which is within the range of prices typically charged by UK energy companies.
Assuming that it requires 20 W or 1/50 kW to produce thought, charging 16p per kWh means that one penny can purchase 1/16th of a kWh. Therefore the length of time (in hours) a penny can purchase thought for is (1/16)÷(1/50)=3.125.
Assuming that it is possible to think as fast as you can speak, the student suggests that 3 hours, 7 minutes and 30 seconds of thought and speech can be bought with a penny.
Student Osarenkhoe Uwuigbe said: “This model is likely to be an underestimate as power required for the brain to operate does not necessarily translate to power used in thought. The brain has several autonomic functions it carries out during thought processing and as a result thought processing could not take 100% of the power consumption of the brain.
“Furthermore, it is unlikely that it is possible to think as fast as you speak due to delay caused by biological constrains such as conduction velocity of nerves carrying the signal from the brain to the mouth, the release of Ca2+ ions during muscle contraction of the tongue and lips and so on.”
Dr Cheryl Hurkett from the University of Leicester’s Centre for Interdisciplinary Science said: “An important part of being a professional scientist (as well as many other professions) is the ability to make connections between the vast quantity of information students have at their command, and being able to utilise the knowledge and techniques they have previously mastered in a new or novel context.
“The Interdisciplinary Research Journal module models this process, and gives students an opportunity to practise this way of thinking. The intention of this module is to allow students to experience what it’s like to be at the cutting edge of scientific research.
“The course is engaging to students and the publishing process provides them with an invaluable insight into academic publishing. It also helps students feel more confident when submitting future papers. I find it a very rewarding module to teach and I am always pleased to see my students engaging so enthusiastically with the subject. I encourage them to be as creative as possible with their subject choices as long as they can back it up with hard scientific facts, theories and calculations!”

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Written by physicsgg

August 16, 2015 at 12:38 pm

Whole-central nervous system functional imaging in larval Drosophila

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Written by physicsgg

August 12, 2015 at 6:49 pm

Posted in BIOLOGY