Structure of Starch by pioyi 6 Updated +Created
Starch is packed into semicrystalline granules (containing crystalline and non-crystalline section) called starch granules. These granules are either contained in plant leaves or stored for long term usage in the plant's seeds/roots/fruit. In the leaves, the starch granules are smaller and are located inside chloroplasts. This starch is termed transitory starch and is accessed during the night to provide the plant with energy. The granules contained in the plant's other organs hold starch referred to as storage starch which is reserved for long-term usage. These granules are stored inside special double-envelopped organelles called amyloplasts. Potato tubers contain this type of starch and are used as the potato plant's "battery" when the shoot of the plant has died and thus can not provide the plant with any energy (glucose) via photosynthesis.
The structure of starch granules has been debated and it's not yet clear. Nevertheless, scientists have identified some components. As the two polymers that make up starch are just repeated glucose molecules, starch consists only of glucose. Amylose is polymerized into a coiled chain of glucose molecules (no branching), while amylopectin shows a linear but branched structure. The granules consist of 10-30% amylose (percentage varies depending on source) and 70-90% amylopectin. The branched chains of amylopectin interact together and form double helices while the linear part of amylopectin that is not surrounded by its branches resides together with amylose chains. These amylose chains form the amorphous (non-crystalline) part of the granules while the packed double helices form the crystalline one.
Starch by pioyi 6 Updated +Created
Starch is an organic structure (carbohydrate) composed of two distinct polymers, amylose and amylopectin that are all made up of repeated glucose molecules. It is used as a reserve of energy, providing plants with glucose molecules (and consequently energy) when photosynthesis can not occur (at night or in winter). In humans it's a source of glucose necessary for energy production. Starch is also used in papermaking, glue and laundry.
Earth's magnetic field by Ciro Santilli 35 Updated +Created
Water compass by Ciro Santilli 35 Updated +Created
We define a "water compass" as a compass made by placing a magnet floating on a water surface to reduce friction and allow it to align with the Earth's magnetic field. This is a common children's scientific experiment.
Video 1.
Bar magnet aligns with Earth's magnetic axis by KClassScienceChannel
. Source.
Compass by Ciro Santilli 35 Updated +Created
Torque by Ciro Santilli 35 Updated +Created
Social justice YouTube channel by Ciro Santilli 35 Updated +Created
Social justice by Ciro Santilli 35 Updated +Created
Bavaria by Ciro Santilli 35 Updated +Created
State of Germany by Ciro Santilli 35 Updated +Created
Falun mine by Ciro Santilli 35 Updated +Created
A hugely important copper mine in Sweden.
Selenium was initially discovered from ore from this mine.
Video 1.
Mining Area of the Great Copper Mountain in Falun, Sweden by World Heritage Journeys
. Source.
Video 2.
Falun mine tour by Focus by Sohaib
. Source. Not English, but we can see the tour images at least.
Sweden by Ciro Santilli 35 Updated +Created
Czech Republic by Ciro Santilli 35 Updated +Created

Pinned article: ourbigbook/introduction-to-the-ourbigbook-project

Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 5. . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact