In continuum mechanics, stress is a physical quantity that expresses the internal forces that neighbouring particles of a continuous material exert on each other, while strain is the measure of the deformation of the material.

For example, when a solid vertical bar is supporting an overhead weight, each particle in the bar pushes on the particles immediately below it. When a liquid is in a closed container under pressure, each particle gets pushed against by all the surrounding particles.
The container walls and the pressure-inducing surface (such as a piston) push against them in (Newtonian) reaction.
These macroscopic forces are actually the net result of a very large number of intermolecular forces and collisions between the particles in those molecules. Stress is frequently represented by a lowercase Greek letter sigma (σ).
Residual stresses inside a plastic protractor are revealed by the polarized light.
Strain inside a material may arise by various mechanisms, such as stress as applied by external forces to the bulk material (like gravity) or to its surface (like contact forces, external pressure, or friction).
Any strain (deformation) of a solid material generates an internal elastic stress, analogous to the reaction force of a spring, that tends to restore the material to its original non-deformed state.
In liquids and gases, only deformations that change the volume generate persistent elastic stress.
However, if the deformation changes gradually with time, even in fluids there will usually be some viscous stress, opposing that change. Elastic and viscous stresses are usually combined under the name mechanical stress.
Significant stress may exist even when deformation is negligible or non-existent (a common assumption when modeling the flow of water). Stress may exist in the absence of external forces; such built-in stress is important, for example, in prestressed concrete and tempered glass.
Stress may also be imposed on a material without the application of net forces, for example by changes in temperature or chemical composition, or by external electromagnetic fields (as in piezoelectric and magnetostrictive materials).
Virial stress 🧐 is a measure of mechanical stress on an atomic scale for homogeneous systems.

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Pott found an association between exposure to soot and a high incidence of scrotal skin cancer in chimney sweeps. This cancer is now known as Pott's or chimney sweep cancer.

Coal contains trace amounts of naturally-occurring radioactive elements. The process of burning coal at coal-fired power plants, called combustion, creates wastes that contain small amounts of naturally-occurring radioactive material (NORM).

Fly ash particles (a major component of coal ash) can become lodged in the deepest part of your lungs, where they trigger asthma, inflammation and immunological reactions.
Localized Surface Plasmon Resonance - an overview | ScienceDirect Topics

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In some cases, almost 100% of the light energy can be converted to the second harmonic frequency. These cases typically involve intense pulsed laser beams passing through large crystals, and careful alignment to obtain phase matching.

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The entire discussion around Facebook’s disclosures of what happened in 2016 is very frustrating. No exec stopped any investigations, but there were a lot of heated discussions about what to publish and when.


In the spring and summer of 2016, as reported by the Times, activity we traced to GRU was reported to the FBI. This was the standard model of interaction companies used for nation-state attacks against likely US targeted.

In the Spring of 2017, after a deep dive into the Fake News phenomena, the security team wanted to publish an update that covered what we had learned. At this point, we didn’t have any advertising content or the big IRA cluster, but we did know about the GRU model.

This report when through dozens of edits as different equities were represented. I did not have any meetings with Sheryl on the paper, but I can’t speak to whether she was in the loop with my higher-ups.

In the end, the difficult question of attribution was settled by us pointing to the DNI report instead of saying Russia or GRU directly. In my pre-briefs with members of Congress, I made it clear that we believed this action was GRU.
Next.js has taken the web dev world by storm

It’s the @reactjs framework devs rave about praising its power, flexibility, and dev experience

Don't feel like you're missing out!

Here's everything you need to know in 10 tweets

Let’s dive in 🧵


Next.js is a @reactjs framework from @vercel

It couples a great dev experience with an opinionated feature set to make it easy to spin up new performant, dynamic web apps

It's used by many high-profile teams like @hulu, @apple, @Nike, & more

https://t.co/whCdm5ytuk


@vercel @hulu @Apple @Nike The team at @vercel, formerly Zeit, originally and launched v1 of the framework on Oct 26, 2016 in the pursuit of universal JavaScript apps

Since then, the team & community has grown expotentially, including contributions from giants like @Google

https://t.co/xPPTOtHoKW


@vercel @hulu @Apple @Nike @Google In the #jamstack world, Next.js pulled a hefty 58.6% share of framework adoption in 2020

Compared to other popular @reactjs frameworks like Gatsby, which pulled in 12%

*The Next.js stats likely include some SSR, arguably not Jamstack

https://t.co/acNawfcM4z


@vercel @hulu @Apple @Nike @Google The easiest way to get started with a new Next.js app is with Create Next App

Simply run:

yarn create next-app

or

npx create-next-app

You can even start from a git-based template with the -e flag

yarn create next-app -e https://t.co/JMQ87gi1ue

https://t.co/rwKhp7zlys

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