Gases or liquids can be unevenly distributed between two areas. If one area has a higher concentration than the other then the differance between these two areas is termed the concentration gradient. The equality is then corrected by the movement of the molecules down this so called gradient from the region of high concentration to that of low. This process is passive as the molecules do not have to be forced to do this and it is reffered to as diffusion.

Learn about diffusion, osmosis, and concentration gradients and why these are important to cells. Created by Sal Khan.

This simple demonstration shows the movement of molecules from a higher concentration to a lower concentration across a permeable membrane.

Materials required for this activity are simple and easily obtained.

This course is a three-part series which explains the basis of the electrical, optical, and magnetic properties of materials including semiconductors, metals, organics, and insulators. We will show how devices are built to take advantage of these properties. This is illustrated with a wide range of devices, placing a strong emphasis on new and emerging technologies.
The first part of the course covers electronic materials and devices, including diodes, bipolar junction transistors, MOSFETs, and semiconductor properties. The second part covers optical materials and devices, including photodetectors, solar cells (photovoltaics), displays, light emitting diodes, lasers, optical fibers, optical communications, and photonic devices. The final part of the series covers magnetic materials and devices, including magnetic data storage, motors, transformers, and spintronics.
This course was organized as a three-part series on MITx by MIT’s Department of Materials Science and Engineering and is now archived on the Open Learning Library, which is free to use. You have the option to sign up and enroll in each modules if you want to track your progress, or you can view and use all the materials without enrolling.

Understanding how channel proteins and carrier proteins can facilitate diffusion across a cell membrane (passive transport).

This course covers the fundamental driving forces for transport—chemical gradients, electrical interactions, and fluid flow—as applied to the biology and biophysics of molecules, cells, and tissues.

This course introduces the basic driving forces for electric current, fluid flow, and mass transport, plus their application to a variety of biological systems. Basic mathematical and engineering tools will be introduced, in the context of biology and physiology. Various electrokinetic phenomena are also considered as an example of coupled nature of chemical-electro-mechanical driving forces. Applications include transport in biological tissues and across membranes, manipulation of cells and biomolecules, and microfluidics.

Revised for Human Gas Exchange and simplified somewhat.By the end of this section, you will be able to:Name and describe lung volumes and capacitiesUnderstand how gas pressure influences how gases move into and out of the body

This work consists of original content and adapted OpenStax content. Each image is attributed with the source page in the figure description, in accordance with each respective license. OpenStax content has been remixed into the “Theory and Background,” “Lab Examples,” and “Relations to Health Sciences” sections of this work. OpenStax remixing consists of rearrangement and minor instructional design augmentations. All other sections within this work are originally created content.

Students are challenged to think as biomedical engineers and brainstorm ways to administer medication to a patient who is unable to swallow. They learn about the advantages and disadvantages of current drug delivery methods—oral, injection, topical, inhalation and suppository—and pharmaceutical design considerations, including toxicity, efficacy, size, solubility/bioavailability and drug release duration. They apply their prior knowledge about human anatomy, the circulatory system, polymers, crystals and stoichiometry to real-world biomedical applications. A Microsoft® PowerPoint® presentation and worksheets are provided. This lesson prepares students for the associated activity in which they create and test large-size drug encapsulation prototypes to provide the desired delayed release and duration timing.

Hands-on introduction to NMR presenting background in classical theory and instrumentation. Each lecture is followed by lab experiments to demonstrate ideas presented during the lecture and to familiarize students with state-of-the-art NMR instrumentation. Experiments cover topics ranging from spin dynamics to spectroscopy, and include imaging.

This resource is a video abstract of a research paper created by Research Square on behalf of its authors. It provides a synopsis that's easy to understand, and can be used to introduce the topics it covers to students, researchers, and the general public. The video's transcript is also provided in full, with a portion provided below for preview:

"For more than 5,000 years, metals and alloys have been formed in roughly the same way—propelling civilization from the Bronze Age to the Industrial Revolution and to the Aerospace Age. Now there’s a new technique on the horizon that could help us take another big leap forward. It’s called high-entropy alloying, and the latest Focus issue of the Journal of Materials Research showcases scientists’ and engineers’ latest efforts in understanding high-entropy alloys and their potential applications. Traditional physical metallurgy uses an element with attractive properties as a base, and adds small amounts of other elements to improve those and other properties. Over thousands of years, various elements have been used as the base: first copper, then iron, then one by one across the periodic table, until researchers developed the first titanium alloys in the 1950s. It’s a method that’s proven incredibly effective. But there are signs that the approach may be reaching its natural limit..."

The rest of the transcript, along with a link to the research itself, is available on the resource itself.

By the end of this section, you will be able to:Describe the passage of air from the outside environment to the lungsExplain how the lungs are protected from particulate matter

This course provides an introduction to complex networks and their structure and function, with examples from engineering, applied mathematics, and social sciences. Topics include spectral graph theory, notions of centrality, random graph models, contagion phenomena, cascades and diffusion, and opinion dynamics.

This course introduces three main types of partial differential equations: diffusion, elliptic, and hyperbolic. It includes mathematical tools, real-world examples and applications.

Introduction to Sociology 2e adheres to the scope and sequence of a typical, one-semester introductory sociology course. It offers comprehensive coverage of core concepts, foundational scholars, and emerging theories, which are supported by a wealth of engaging learning materials. The textbook presents detailed section reviews with rich questions, discussions that help students apply their knowledge, and features that draw learners into the discipline in meaningful ways. The second edition retains the book’s conceptual organization, aligning to most courses, and has been significantly updated to reflect the latest research and provide examples most relevant to today’s students. In order to help instructors transition to the revised version, the 2e changes are described within the preface.

Discuss the roles of both high culture and pop culture within societyDifferentiate between subculture and countercultureExplain the role of innovation, invention, and discovery in cultureUnderstand the role of cultural lag and globalization in cultural change

Using ordinary household materials, student “biomedical engineering” teams design prototype models that demonstrate semipermeability under the hypothetical scenario that they are creating a teaching tool for medical students. Working within material constraints, each model consists of two layers of a medium separated by material acting as the membrane. The competing groups must each demonstrate how water (or another substance) passes through the first layer of the medium, through the membrane, and into the second layer of the medium. After a few test/evaluate/redesign cycles, teams present their best prototypes to the rest of the class. Then student teams collaborate as a class to create one optimal design that reflects what they learned from the group design successes and failures. A pre/post-quiz, worksheet and rubric are provided.

This course presents a unified treatment of phenomenological and atomistic kinetic processes in materials. It provides the foundation for the advanced understanding of processing, microstructural evolution, and behavior for a broad spectrum of materials. The course emphasizes analysis and development of rigorous comprehension of fundamentals. Topics include: irreversible thermodynamics; diffusion; nucleation; phase transformations; fluid and heat transport; morphological instabilities; gas-solid, liquid-solid, and solid-solid reactions.