Biology & Medicine

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MRI Machines and You

Keywords:

Quantum Mechanics + Radio Waves = Pictures of your Brain

An explanation of how MRI machines take advantage of nuclear spins to image precise slices of a person.

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4 years 27 weeks ago

How big was the aerodynamic force on Felix Baumgartner at 1342 km/h? (Or on Alan Eustace at 1321 km/h?)

Keywords: aerodynamics, drag, felix baumgartner, free fall

Did you watch Felix Baumgartner jump out of a balloon gondola at an altitude of 39 km? Here's a question for your physics students, or even your physics teacher! How big was the drag force on Felix Baumgartner at his maximum speed of 1342 km/h? Pretty enormous, right? Wrong.

Knowing next to nothing about how aerodynamic drag varies as one hits the sound barrier, there is very simple way to assess the aerodynamic drag on a falling object at its maximum speed. Even at 1432 km/h. In fact the maximum aerodynamic drag occurs afterwards when the falling object is slowing down in the denser lower atmosphere. To asses how big the force was on Felix Baumgartner, we create a simple mathematical model of his fall.

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4 years 38 weeks ago

How much do grade 10 students know about our energy consumption?

Keywords:

Do students understand how similar we are to the machines we make?

The human body and the internal combustion engine are quite similar in that they are both heat engines requiring chemical energy to run.
By placing a question related to this notion on a national science contest, we attempted to discover what Grade 10 students think.

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5 years 19 weeks ago

Commuting by car or cycle - which is better?

Keywords: bicycle, Carbon footprint, consumption, cycling, energy, Food, spreadsheets

It's not actually that clear...

We set out to find how much of a change it would make environmentally if one cycled instead of drove to work and then further expanded our findings to include the variables of diet composition and material goods ownership.

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5 years 22 weeks ago

Food, Energy and the Environment

Keywords: energy balance, Food, greenhouse gases

How do we feed nine billion people without destroying our environment?

The primary function of food is to provide our bodies with energy. Most of this energy comes ultimately from oil, with a little sunlight added, and its production is an energy-inefficient process.

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5 years 22 weeks ago

Steam Burns

Keywords: heat, heat of vaporization, phase changed, specific heat, temperature change

Why can steam at 100 degree celsius burn worse than boiling water at 100 degree celsius?

This article explains why steam at 100 degC transfers more thermal energy to your skin than an equivalent mass of boiling water at 100 degC.

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5 years 23 weeks ago

Chaos, Frog Ponds, and Red Tide

Keywords: Chaos, Complexity, Population Biology

Sometimes things are less complicated than they seem...

Under certain circumstances, simple equations can model complicated results. We can make a model of a frog pond that shows this type of behaviour. Sometimes this complex behaviour can lead us to identify incorrect, or not entirely correct, causes for the behaviour.

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5 years 28 weeks ago

Interference and Colour Part III - Mathematics of Thin-Film Interference

Keywords: absorption, colour, diffraction grating, index of refraction, inherent phase difference, interference, light, path length difference, phase, phase difference, phase shift, reflection, thin-film interference, transmission, waves

How can alternating layers in a beetle's shell give the beetle brilliant colour?

This article explains how to derive the conditions for constructive interference for thin-film interference and finds the thicknesses of alternating layers of melanin and protein to give constructive interference at 635 nm.

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5 years 29 weeks ago

Interference and Colour, Part II - Thin Film Interference

Keywords: absorption, colour, diffraction grating, index of refraction, inherent phase difference, interference, light, path length difference, phase, phase difference, phase shift, reflection, thin-film interference, transmission, waves

What does this beetle and a soap bubble have in common?

This article explains how by having a thin-film the waves reflecting off of the boundaries between media can interfere and result in coloration.

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5 years 31 weeks ago

Interference and Colour, Part I - Diffraction Gratings

Keywords: absorption, colour, diffraction grating, index of refraction, inherent phase difference, interference, light, path length difference, phase, phase difference, phase shift, reflection, thin-film interference, transmission, waves

What gives this beetle its rainbow colours?

This article describes how colouration of an object can arise due to interference of the light waves being reflected from the object.
Periodically arranged structures which act as point sources are one means of creating the condition that at certain angles only one specific wavelength will interfere constructively. The wavelengths that interfere constructively determine the colour of the object.
Examples of colouration in beetles by interference due to periodic structures is given.

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5 years 39 weeks ago
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