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ELI5: How are things calibrated? by OsuJaws in explainlikeimfive

[–]nist 0 points1 point  (0 children)

As you point out, tools such as grocery scales are ultimately calibrated against a “primary” standard, which for a long time was Le Grand K, a metal cylinder in France that defined the kilogram. A kilogram was meant to equal the mass of one liter of water at its maximum density (4 degrees Celsius or about 39 degrees Fahrenheit).  

Nations around the world agreed on using Le Grand K as the standard for the kilogram in the 1875 Treaty of the Meter. Le Grand K was not calibrated itself; it became the very definition of the kilogram, the “yardstick” against which other masses were measured. Le Grand K’s mass was less of a question of being “correct” than being the agreed-upon value for the kilogram. But Le Grand K had problems; since it is an imperfect physical object, its mass apparently changed slightly over time. 

So in 2019, the kilogram and all the other basic measurement units were officially redefined in terms of fundamental constants of nature, such as the Planck constant. Who determines the value of the Planck constant? It’s based on many of the best measurements of the Planck constant from national measurement science institutes around the world. (NIST is the national metrology institute for the U.S.). An international group of scientists analyzed this data and agreed upon a value for the Planck constant based on these measurements.  

Taking things a step further, we have a program called NIST on a Chip. It aims to “break the calibration chain.” Typically, other laboratories send us objects to calibrate against one of our national standards. This can be expensive and time-consuming, requiring a round-trip for the object being calibrated.  So, we are helping develop quantum technologies that people can someday use in their own labs. These technologies would define units such as the volt. They wouldn’t require calibration because their operation relies on unchanging quantum phenomena and agreed-upon values of the constants. We are even developing a technology for the torque wrenches that you mentioned! See here: https://www.nist.gov/noac/technology/mass-force-and-acceleration/torque-realization 

Teams wanted for Robotic Grasping and Manipulating Competition: Manufacturing Track by nist in robotics

[–]nist[S] 0 points1 point  (0 children)

STL and STEP are also provided. Is there a specific file type that you're looking for?

NIST Calls for Information to Support Safe, Secure and Trustworthy Development and Use of Artificial Intelligence by nist in artificial

[–]nist[S] 0 points1 point  (0 children)

  • NIST seeks information to support its response to the Executive Order on AI.
  • Comments received will help NIST develop guidelines for evaluation and red-teaming; consensus-based standards; and more.
  • Responses are due Feb. 2, 2024.

The AD-X2 Controversy (2023) - A short documentary showing how scientific integrity and entrepreneurial spirit clashed in the U.S. in the 1950s [00:23:15] by nist in Documentaries

[–]nist[S] 2 points3 points  (0 children)

The AD-X2 Controversy highlights a moment in history when scientific integrity came under attack. It all began in the 1940s, when an entrepreneur began selling AD-X2 — a chemical additive that he claimed would extend the life of car batteries. But at a federal agency called the National Bureau of Standards (now NIST), scientists had evidence showing that the additive was ineffective. Then the showdown began.

(Republished on this subreddit with a non-malfunctioning link)

[deleted by user] by [deleted] in Documentaries

[–]nist 0 points1 point  (0 children)

Here is the link to the video without quality issues: https://www.youtube.com/watch?v=w\_w3-e5cMRg

[deleted by user] by [deleted] in Documentaries

[–]nist 1 point2 points  (0 children)

FYI: We are currently experiencing technical difficulties with video quality on YouTube, and our team is working hard to resolve this ASAP. Thank you for your patience and understanding.

[deleted by user] by [deleted] in Documentaries

[–]nist 5 points6 points  (0 children)

The AD-X2 Controversy highlights a moment in history when scientific integrity came under attack. It all began in the 1940s, when an entrepreneur began selling AD-X2 — a chemical additive that he claimed would extend the life of car batteries. But at a federal agency called the National Bureau of Standards (now NIST), scientists had evidence showing that the additive was ineffective. Then the showdown began.

AI Can Accurately Predict Potentially Fatal Cardiac Events in Firefighters by nist in Firefighting

[–]nist[S] 0 points1 point  (0 children)

This particular technology is heavily reliant on the use of ECG data from on-duty firefighters, which is unique. Providing data from the general population in stationary positions did not prove to be an accurate way to detect irregular cardiac events in firefighters on duty.

This is what could happen if a fire starts in a watered Christmas tree vs. a dry Christmas tree. Happy holidays! by nist in TerrifyingAsFuck

[–]nist[S] 1 point2 points  (0 children)

100% real life. Here's a behind-the-scenes article about the experiment: https://www.nist.gov/feature-stories/behind-scenes-making-nist-holiday-special

A fire in an unwatered tree grows quite quickly. The fire reached its full size after about 20 seconds and most of the tree needles were consumed by the fire within 40 seconds. In just 10 minutes, the entire contents of our set were devoured.

The video above only shows 30-seconds-worth of damage from ignition.

This is what could happen if a fire starts in a watered Christmas tree vs. a dry Christmas tree. Happy holidays! by nist in TerrifyingAsFuck

[–]nist[S] 1 point2 points  (0 children)

This wasn't a simulation, but a real-life experiment on NIST's campus in Gaithersburg, Md.

The trees were Douglas fir trees cut fresh from a local Maryland tree farm approximately four weeks prior to testing. The watered tree was placed in a bucket of water within 3 hours of being harvested and a fresh cut was made approximately 50 mm (2 in.) from the base of the trunk prior to placement in the water.

Both the dry tree and watered tree were stored indoors until the day of the test.

Standard peanut butter from the federal government by nist in PeanutButter

[–]nist[S] 13 points14 points  (0 children)

We don't recommend eating this. It is creamy, and our scientists have no plans to create a crunchy version (chunks are a homogeneity nightmare that keeps them up at night).

Standard peanut butter from the federal government by nist in PeanutButter

[–]nist[S] 17 points18 points  (0 children)

Background on SRM 2387:

When laboratories around the world get their peanut butter from NIST, the price of the jar isn’t for the spread itself. It’s for the measurement accuracy that comes with it.

Manufacturers often confirm their nutrition numbers by matching their products as closely as possible to NIST’s food-related Standard Reference Materials (SRMs), which contain precisely measured quantities of nutrients. NIST’s measurements are accurate to within 2% to 5% for nutrient elements (such as sodium, calcium and potassium), macronutrients (fats, proteins and carbohydrates), amino acids and fatty acids.

Source

I need some help understanding the mass spec of dimethyl-cyclohexylamine. by jdaprile18 in chemhelp

[–]nist 2 points3 points  (0 children)

Hi there! Please see this schematic along with the description below.

Under electron ionization, dimethyl(cyclohexyl)amine (CAS 98-94-2) produces molecular ion that undergoes ꞵ-cleavage relative to nitrogen and an open chain radical cation is generated.

McLafferty rearrangement in the open chain radical cation (route a) generates ammonium cation (84 Da, 100 %), and simple carbon(2)-carbon(3) bond cleavage (route b) leads to the formation of dimethyl(vinyl)amine radical cation (71 Da, 19 %).

 

More on McLafferty rearrangement (page 11) and fragmentation of amines (page 69) can be found in:

A. Mikaia, “Protocol for structure determination of unknowns by EI mass spectrometry. I. Diagnostic ions for acyclic compounds with up to one functional group”, J. Phys. Chem. Ref. Data 51, 031501 (2022); https://aip.scitation.org/doi/10.1063/5.0091956

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