Particle Sizers


What is a particle sizer and how does it work?


A particle sizer provides scientists with information on the whole range of particles that may be in a sample. The sample could be, for example, a dry industrial powder, a soil sample, or particles within a water sample collected from a river or lake. Often particle size is required to help understand a chemical reaction, or the settling or transport of particles and their associated pollution within a natural (e.g. river) or engineered (e.g. sewer) system. There are many different types of particle sizers. The most common particle sizers use particle settling velocity, lasers, microscopes or electrical resistance to measure the size range of particles in a sample. Generally the output from a particle sizer will be called a “sediment or particle size distribution”.

- Ian Droppo



Cardiac Pacemakers


Hello, can you please tell me how I can create a fake cardiac pacemaker so that it acts like a real cardiac pacemaker? Thank you.


In response to your question we received a solution that should be manageable for a 10 year old.

What your son needs to build this model are 3 D cell batteries lined up end to end (positive-negative-positive-negative-positive-negative) probably taped together to ensure they stay in contact. Then connect one end with copper wire to a lead on a push button (he’d have to buy this, probably at The Source or Radio Shack?). A second piece of copper wire has to be wound around a nail and then you need to connect one end of the wire to the batteries and the other end to the push button. Next to the head of the nail is a washer, on a flexible rod and base. As the student presses the button, a magnetic field would be created around the nail and will attract the washer. Essentially, the student is acting like the circuit board on the pace maker and detecting an irregular or absent cardiac rhythm. By pushing the button, the “computer” (student) is sending an electrical output to the heart (the washer on the rod) and resetting the rhythm.

Alternatively, he could attach the copper wires to a small light bulb and the bulb will light up each time the student “shocks” the heart.

- Eilean McKenzie





For education purposes, I want to simulate an ultrasound and an x-ray (individually) passing through material such as a weld. I have been looking at ray tracing. Where would you suggest I begin? Also is there any funding available for such a start-up?


According to our experts in the field it is difficult to obtain this type of simulated assessments using low cost simulations. This question might be related to critical studies on safe encapsulation of nuclear waste and if so the approach needs a high level of accuracy, repeatability and be accredited by related decision makers and agencies. Additionally, aging of weld, bond and material can get very difficult to predict.

In short, it is possible to use simulation (could use ray tracing or method of moment) of an ultrasound and an x-ray (individually) passing through material such as a weld to predict the degree of usability of such techniques to detect defects. But, depending on the level of accuracy, it appears to be difficult to do so thus far and will require substantial experimentation to perfect and calibrate using real material and instruments (ultrasound and x-ray (individually) passing through material). Currently there are many instruments that can measure accurately such defects so a good approach could be to combine simulation capabilities with real trials with appropriate instruments.

Please consider the following references: NDT | NRC | K Labs

If there is funding for a start-up, National Research Council Canada would be in a better position to provide you with details.

- Paul Labbé



Laser compression


Can compression of laser materials be one solution of increasing Laser efficiency based on the fact that compression makes energy states closer to each other, consequently decrease the energy required for electrons to transfer from one energy state to another?


Great question! Of course, the answer is, "it depends". To understand it, let's look at what a laser is. 'LASER' is an acronym that stands for Light Amplification by the Stimulated Emission of Radiation. All lasers are composed of a gain medium, an excitation source, and an optical feedback cavity. Laser action, or lasing, occurs in the gain medium of the laser. You can always determine what the gain medium is by the name of the laser. For example, a mixture of helium and neon gas is the gain medium of a HeNe laser, and atoms of semiconducting elements are the gain medium in a diode laser, such as those found in laser pointers. The excitation source excites the electrons in the gain medium to a higher energy level. When a photon of light passes through the excited gain medium, it stimulates emission of light radiation as the electrons relax to a lower energy level. Therefore, the wavelength of a laser is dictated by the energy difference between the lower and higher energy levels in the lasing process.

The efficiency of a laser is the ratio of excitation source power to emitted power, and depends on the complex interplay of both amplification processes and losses within the optical feedback cavity. Gain comes exclusively from the gain medium, and depends on things like the concentration of the gain medium, the fraction of excited states that decay through emission of radiation, and the efficiency of exciting the gain medium electrons to the higher energy level of the lasing process. Losses can come from many places, including the scattering of light, reflective losses from each optical surface, non-radiative decay processes from the higher energy level in the lasing process, absorption of emitted light by the gain medium, and spontaneous emission of light into directions different than the laser beam. Typical laser efficiencies range from less than 1% to at most around 30%. Different types of lasers have different intrinsic efficiencies.

Soooo... The short answer is that bringing energy levels closer together changes the wavelength of the laser and usually increases the non-radiative processes more efficiently than the radiative decay of the higher energy level in the lasing process. Therefore, these effects would decrease lasing efficiency. However compression may also increase the concentration of the lasing medium, increasing the lasing efficiency. The net effect will depend on the balance between these two factors. Some lasers, like the ion lasers, use magnets to compress the gaseous ions resulting in higher lasing efficiencies because of a higher gain medium concentration. The compression isn't so drastic that it changes the energy levels significantly.

- Glen Loppnow





How does Fixed broadband work? How does mobile broadband work?


Broadband is a technical term that refers to the ability of a transmission medium to transport multiple signals and traffic types simultaneously.  For instance, being able to share a wireless modem connection with many people in your house.   A very nice description of the different ways that the term is used is on the wikipedia page for broadband under the heading In Telecommuncation (  The mobile phone industry tends to use the term broadband to refer to internet access, although technically this is not correct as narrowband, voice band, or dial-up connectivity to the internet is still possible.

Mobile broadband is a marketing term for accessing the internet through some portable (mobile) device.  This is generally done through the use of cell towers for transmission of data to and from an internet gateway, and requires devices and infrastructure with the technology to support this (e.g. some 2G, 3G or 4G technology).  The terms "mobile broadband" and "cellular broadband" tend to be used somewhat interchangeably. 

Fixed broadband refers to the use of transmission towers (ground stations) to transmit data to and from the internet gateway and the client's computer, in a similar way that cell phone towers fulfill a similar purpose for mobile broadband.  Equipment for fixed broadband access includes a transceiver for communicating with the ground stations.  This consists of some type of antenna (e.g. dish-style) and a radio transmitter.  This type of equipment is used only for communication with ground stations (fixed stations) and cannot be used for satellite-based internet access.   Limitations include the necessity of line of sight access between the dish and the ground station; and in fact the quality of service can be negatively affected by atmospheric conditions such as rain or fog.  In addition, roaming can't be supported, since the service is tied to one physical access point (ground station).

Wireless broadband is used to provide both fixed and mobile internet access; that is, the basic underlying idea allowing data transmission over radio waves for both mobile broadband and fixed broadband is the same.  The client (either the dish and transmitter or your cell phone) and the towers (either a cell phone tower or a ground station) send packets of digital information back and forth to each other via radio waves, and between them they use some network rules, or protocols, to ensure that the packages, or messages, aren't lost.   Standards and protocols for mobile broadband have to allow for movement from one cell tower to another, while fixed broadband protocols don't have to deal with this.    In both cases the protocols must cover exactly how the radio waves are used to transmit your digital data and how the frequencies will be shared, and how the underlying network connecting your computer to the internet operates.  There are many many different protocols for each of these different layers of operation, but to ensure that there is a base level of quality and that different networks can communicate with each other the Institute of Electrical and Electronics Engineers (IEEE) provides a set of standards that the industry is expected to adhere to when developing new protocols and new technologies to work with the protocols.

For details on the different technologies I would recommend this 2005 paper:, or this website (date not given) also provides a nice overview of both mobile broadband (they call it cellular broadband or mobile wireless) and fixed wireless:

-Jackie Rice



Transporting Crude Oil


After watching Exploring Oil Sands Science, I'd like to know if transporting crude oil, by whatever means, is dangerous. It seems to me that transporting gasoline, diesel and plastic is less dangerous. Why is crude oil not transformed on-site in Alberta in petrochemical plants like those found in Montréal? How is plastic transported and in what form?


This is a good question. First, transporting crude oils (by pipeline, tanker trucks, or railways) is no more dangerous than transporting gasoline, jet fuel, diesel or any other petroleum liquid product by using the same means. Essentially, crude oils, gasoline, jet fuel and diesel and other petroleum liquid products have similar properties in terms of safety. Plastic is different because it is a solid with a very low risk of explosion, spills, combustion etc.

Second, transforming crude oils into gasoline, diesel and other petroleum products (including plastic, rubber, fiber etc.) requires refineries and petrochemical plants, which need huge capital investment and other required infrastructure (water, power, natural gas, etc.) to build and operate. In addition, these plants will have to be operated at relatively large scale to be economically profitable. Some oil fields may not be able to produce enough crude oil feedstocks. Furthermore, even refineries are built in places close to oil fields, the refined products (gasoline and diesel) will have to be transported and distributed through pipelines, trucks and railways, which pose similar public safety and environmental risks as transporting crude oils. Therefore these refineries and plants are normally built in populated areas (close to big cities) where the products are needed most and easily distributed. Pipeline systems provide refineries more flexibility to get the crude oil feedstocks they need so they do not have to rely on the crude oil from a particular region/oil fields (otherwise the refinery will have to be shut down if there is a major problem at a nearby oil field).

Third, companies always want to make the most economic benefits. They do various economic analyses to determine where these refineries and plants should be built. Environmental regulations and other local limitations (labor market, available resources etc.) are also important factors to consider.

- Jinwen Chen

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