Brief Updates

If you follow Cath @CathonSci on twitter, and I think she had also mentioned this several posts ago, we have travelled to a “new” “country” and have taken some time in the past two months to settle in to our new home, and for both of us: a new  job. Thank you again for staying with us during this period of infrequent updates.

Since both of us are on contract with a known end date, we still consider ourselves Canadian Bloggers blogging from abroad.

“Country” — as we all know that Hong Kong is not a country by itself but rather a special administrative region.

“New” — because in no way is Hong Kong new to us, but neither of us have been back in a while. Not to mention spending time here on holiday and living & working here is a big difference. A lot of things are new to us this time around, the trends have change, the atmosphere have change, and the culture have change.

Introducing a new Blog in our family

Cath has started a new blog “Thoughts at 3:15” to document our new adventure.

“This blog is meant to be a place to share my experience of living in Hong Kong, a collection of photos and random thoughts about the city”

Don’t worry though, Cath will remain as the main contributor here at (BS) Clarified.

Some Plans for the Future

I would also like to share some plans I have been thinking about (for a while) regarding this blog. So far, we’ve have quite enjoyed the simplicity of WordPress.com. It has offered us easy to set up themes and layouts.

I am considering moving to a hosted wordpress site to gain a bit more flexibility with the design, layout, and eventually contents as well. However, transferring content is easy but transferring readership may not be easy. So what I would like to know is how many of you, our dear readers, will follow us at the hypothetical new site?

Secondly,  self hosting does come with a cost. It is not terribly expensive, but the little bits can accumulate over the years.

So I’ve come to the dilemma I’ve seen over and over again on other blogs: Should I monetize the blog somehow to help offset the hosting/domain cost. Please bear in mind that the purpose of (BS) Clarified will always be to educate the public about the newest advances in science. We are not aiming to make a fortune; all we are aiming for is to make enough to cover hosting/domain cost and maybe the very occasional beer, coffee, tea, or sweets as fuel and encouragement.

Bearing that in mind, here’s the poll:

Please let us know what you think. You can also let us know what you think in the comment below.

Thank you again for staying with us, and remember please subscribe and tell your friends.

P.S. of course Cath’s new blog Thoughts at 3:15 will also be moved together if I do decide to go for a self hosted wordpress site.

To see this year’s Science as Art winning photos check out the following link.

Winning images from past Science as Art competitions can be found here.

The scanning electron microscope produces black and white images of materials photographed. But sometimes when you stare at theses photo long enough they can start to resemble other things. I think this is a large motivation for this annual competition. Attendees of the MRS annual meeting are invited to submit their photos for the competition. The photo submissions range in the level of editing, from simple false-colouring to complex photo edits involving drawn in objects.

To me the most impressive images are the ones that retain the integrity of the original photo so that the features of material are still recognizable, yet have been transformed into another object or scenery.

For example, this year’s first place photo from Singapore University of Technology and Design’s Yang Hui Ying is of organic nanowires coated with inorganic nanoparticles. With what appears to be minor edits involving cropping and blurring of the background, this photo has been transformed to resemble frost covered pine needles.

Science and art are often separated into unrelated fields, where those in one field often don’t care about those in the other field. But science and art are connected.  Ira Flatow host of Science Friday, quoted Albert Einstein on this connection in his broadcast: “The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science. So the unknown, the mysterious, is where art and science meet.”

Source: The Imaginary Foundation

I think this quote is very true, and the MRS competition does a good job of connecting science and arts based on this idea of mystery. Our understanding of the structure and properties of materials are pieced together from images taken from microscopes, and there’s often a lot that is unknown–even with the images in hand.

So I’m all in favour for more events that bring together these two fields, just like the Beakerhead festival scheduled for this September in Calgary, Canada. Beakerhead is an annual event that that brings together the arts, science and engineering sectors through interactive workshops, performances, installations, and concerts.

Images of our kitchen ceiling light socket where the LED bulb popped out from, the burnt epoxy resin in the discoloured LED bulb, the hole in the LED packaging from the overheating/short circuiting of the LED bulb.

Theoretically, LED light bulbs can last for as long as one hundred thousand hours (~11 years) under perfect conditions (Zhaohui et al. 2011). But just like other light bulbs (e.g. incandescent and CFL), material degradation and damage to the packaging from electrical, thermal, chemical or mechanical stress can lead to its early failure. LED failure usually means the light dims over time or burns out completely. Electric or structural damage can cause the suddenly failure of the LED, like ours which burned out.

The main component of LED light bulbs is the LED-chip, which is a semiconductor that generates light. The chip consists of P-type and N-type semiconductors with a transition layer in between these two types of semiconductors.

But without putting our burned out LED in an electron microscope, it’s hard to say exactly what caused it to fail. A couple of research studies (Lu et al. 2009, Shailesh et al. 2012) looking at ways LEDs can fail, report that thermal or electrical stress are two causes of failure. Thermal stress failure is caused by cyclical heat in the LED where the internal temperature is over its maximum rating.

Two common causes of failure are electrical overstress (EOS) damage and Electrostatic Discharge Breakdown (ESD) (Lu 2009). EOS occurs when a voltage or current level exceeds the rating for periods exceeding 100 to 1000 nanoseconds while the LED is in use (Lu 2009). EOS can be caused by voltage or lightning strikes or temporary and unexpected connection to power or ground according to the study’s authors. EOS can damage the wires inside the LED package or the LED chip itself (Lu 2009). This is a key issue during manufacturing and handling according to Lu (2009).

The transition layer between the P-type and N-type semiconductors of the LED chip is known as a PN junction. In ESD, the junction can breakdown when excessive current flow increases the local temperature (Lu 2009). The heat can destroy the junction, resulting leakage or short-circuit (Lu 2009).

LED packaging serves as the electrical connection between the LED chip and external circuit. The packaging protects the LED chip from damage such as ESD. A GaN-based chip is typically packaged with other materials including an epoxy lens, silicone glue, phosphor coating.
As these materials degrade they can lead to failure of the LED package. For example, interface delamination between layers that make up the LED chip can cause open circuit or heat dispersion problems (Fan et al. 2011).

Researchers are continuously studying to understand the failure mechanisms of LED light bulbs to come up with ways of improving their reliability. One area they are focusing on is improving the heat dissipation of the LED packaging structure. Good heat dissipation will prevent heat from accumulating and raising the temperature of the LED chip.

Additionally, ESD protection circuits have been used to protect against ESD failures by getting the current caused by an electrostatic discharge to bypass the LED and flow through the protection circuit instead. Even though LED bulbs will eventual fail they are currently still reliable alternatives to incandescent bulbs, and the reliability of LED bulbs will likely improve over time.

—
Chen, Z., Zhang, Q., Wang, K., Luo, X., & Liu, S. (2011). Reliability test and failure analysis of high power LED packages Journal of Semiconductors, 32 (1) DOI: 10.1088/1674-4926/32/1/014007

Fan, J., Yung, K., & Pecht, M. (2011). Physics-of-Failure-Based Prognostics and Health Management for High-Power White Light-Emitting Diode Lighting IEEE Transactions on Device and Materials Reliability, 11 (3), 407-416 DOI: 10.1109/TDMR.2011.2157695

Lu, G., Yang, S., Huang, Y. (2009). Analysis on Failure Modes and Mechanisms of LED IEEE DOI: 10.1109/ICRMS.2009.5270043

Shailesh, K.R., Kurian, C.P., Kini, S. G.  (2012). Solid State Lighting Reliability from Failure Mechanisms Perspective: A Review of Related Literature. International Electrical Engineering Journal, 3 (2), 764-768

But aside from residential lighting, retail lighting makes up a significant huge portion of lighting sources. Even in a suburban area like the Tseung Kwan O district in New Territories, Hong Kong, retails signs for grocery stores and shopping malls are brightly lit. The signage lights combined with other artificial lighting sources like street lamps, contribute to Hong Kong’s “light pollution”.

Photo of Tseung Kwan O Olympic Stadium (Photo credit: Wikipedia user Anthony Leung-Mercutiostwin)

Light pollution

“Light pollution” refers to excessive artificial outdoor lightning which includes everything from street lights to neon signs and billboards. This light can have negative effects on humans and wildlife, whether affecting sleeping patterns or disorienting nocturnally migrating birds. The additional light brightens the night sky and making it tough for astronomers and astronomy enthusiasts to see stars and other cosmic objects.

Recently, researchers from Hong Kong Night Sky Brightness Monitoring Network (NSN) reported that the night sky between 8:30 to 11:00 pm over the Hong Kong Space Museum in Tsim Sha Tsui was on average 1000 times brighter than the international standard of dark sky (i.e. the night sky brightness level when not influenced by human made light pollution). The large number of billboards and floodlights nearby contribute to the extreme brightness of the area. Surprisingly even the Wetland Park in the remote area of Yuen Long is over 100 times brighter than the standard dark sky.

Also, the NSN team found that the 12 urban stations were on average about 10 times brighter than the other 6 rural sites. “This conclusively shows that manmade outdoor lightings is the dominant factor in determining the extent of light pollution,” said NSN’s principle investigator Dr Jason Chun Shing Pun in a recent media release.

As you can see Hong Kong has one of the world’s most brightly lit night skies. The map was put together by researchers from the Kitamoto Asanobu/National Institute of Infomatics and represents light pollution data collected from 2010. Take a look at this interactive map to get an idea of light pollution worldwide:

Currently Hong Kong does not have any legislation to address light pollution, according to the WSJ. But the NSN believes that the light pollution data they have collected can serve as a database for HK authorities to use when assessing the need for new rules and regulations to control outdoor lighting. “In addition  to  regulations, we as a society have to make a commitment  to  stop  abusing  the  use  of  outdoor lightings, and to limit its adverse effects to the environment,” said Pun.

Canadian connection to Hong Kong’s light pollution research

The NSN uses portable Sky Quality Meters (SQM)that are imported from Canada to measure the night sky brightness. This instrument is only about the size of a deck of playing cards and can give sky brightness values instantly. The Network uses 17 SQMs at the 18 observations sites, collecting data every minute. The stations are fully automated and real time data is sent back to HKU over the city’s mobile phone network.

Canadian imported Sky Quality Meters (SQM) used by the NSN (Photo credit: HKU)

Public awareness of light pollution

There’s is increasing public awareness for the need to reduce light pollution resulting from the growing number of campaigns and outreach events. Coinciding with WWF’s Earth Hour on Saturday, The University of Hong Kong  (HKU) is hosting a Light Pollution Science Roadshow in the Avenue of Stars in Tsim Sha Tsui, on Saturday. Participants will be able to use Real-time sky brightness measurement equipment to have first hand look at Hong Kong’s light pollution. So if you happen to be in the area tomorrow, be sure to check out this event!

First, a disclaimer: I am not writing this to endorse or discredit any products or companies I have mentioned in this blog post.  I am simply curious what I can find on the internet that is freely available for the average Joe.  And if you haven’t guess this by now, YES this is just a filler piece of random factoids, and does not necessarily have any scientific significance and may not be of interest to anyone.

The story begin when I decided to have a can of coke the other day and noticed that one of the ingredient is phosphoric acid. Phosphoric acids is something I used quite often in my research for electro-polishing copper.In fact, my friends and I have even successfully electro-polish copper with cola (a task usually done with phosphoric acid) albeit it leave a sticky sugary residue on the copper. Of course, cola is not as efficient as lab grade phosphoric acid. The concentration of cola is certainly much much much much lower so that it is safe for human consumption without making us sick.  We had even used it successfully as a paint stripper, but that’s another story.

This is not the first time that I noticed phosphoric acid is an ingredient in most cola drinks, but it reminded me that cola drinks consist of this chemical (amongst other) and it is a chemical itself by definition. From our mandatory safety training, all chemicals should have a Material Safety Data Sheet (MSDS) available, usually provided by the manufacturers or retailers of chemicals, that lists all the properties, warnings, hazards, health & safety information,etc. So combining these thoughts, I started googling whether something like Coca-Cola would have a MSDS readily available.

From my “research” by means of Google, I have found that the MSDS is not necessarily required for food items destined to be on the retailer’s shelf directly (there are exceptions). Which means the MSDS for food items can be hard to find. But Google have led me to the MSDS database of Gordon Food Service (a major food service provider in North America). Lo and behold there are a huge list of pops including Coca-Cola. While the MSDS were largely uninteresting, most listing the chemical (read: products) as non-hazardous, non-corrosive to skin, not an irritant to eyes and skin, etc. (why would it be listed otherwise if it is safe to consume) this has spark me to wonder what other MSDS of food products I can find from various retailers’ or manufacturers’  websites.
The first thing I thought of was coffee. I couldn’t find anything for coffee, but I did find the MSDS for pure caffeine from quite a few chemical retailers (e.g. Sciencelab, Sigma-Aldrich, Alfa Aesar). Turns out pure caffeine is an eye and skin irritant, and it’s hazardous to ingest or inhale. The MSDS also contain this statement “The substance may be toxic to heart, gastrointestinal tract, central nervous system (CNS).”  The lowest dose for the effect of toxicity to become apparent is listed as 192-400 mg/kg for adults.

Health Canada list that an average cup of coffee may contain anywhere from 76 – 179 mg of caffeine in coffee. Whereas, Walpol et al. have published in the journal BMC Public Health that the global average body mass is 62 kg (unfortunately this data is from 2005, although the paper was published in 2012). Which means that Coffee would become toxic to the average human if one drinks more than 138-156 cups of coffee in a short period of time (assuming you drink faster than your body can process the caffeine).

As a side note: the average north american body mass is 80.7 kg (~34% of the weight of the entire world populations), whereas the average asian has a body mass of 57.7 kg.

What about other caffeinated drinks?  Health Canada list that a can of cola drink contains 36 – 46 mg of caffeine, so that’d come out to 330 – 539 cans in a really short period of time for caffeine toxicity to kick in for the average human.

From the looks of it, we probably get what’s known as water poisoning before caffeine in normal drinks have toxic effects. Speaking of which, there’s a MSDS for water sometimes listed as dihydrogen oxide. In fact, the MSDS for water is usually the example they give during safety training. Of course, water is non-toxic, non-hazardous, etc. However one of the MSDS list something interesting points, it says that in case of eye contact and skin contact, rinse with water (great way of getting rid of water by rinsing with more water). In any case, it list the LD50 to be 90 mL/kg. LD50 is a measure of toxicity, it is the dose that leads to 50% of the test subjects (usually human analogues like lab rats or mice) to die from toxic effects. From this, we can approximate that if we drink 5580 mL (~22 cups) of water quicker than we can pass it out of our body, it would likely be lethal (we’ll probably be sick way before this point anyways).

Other interesting MSDS that I have come across during my search:

Olive Oil – apparently a minor irritant to skin and eye contact, and slightly hazardous in case of ingestion or inhalation; reactive with oxidizing agents & acids.

Cocoa Butter – not toxic or hazardous, *phew* chocolate is still safe to eat. But chocolate also contains caffeine, and  Health Canada list that 28 g of milk chocolate has about 7 mg of caffeine. To reach the lowest toxic limit of caffeine, it would take 47 -99 kg of chocolate in a time period faster than you can process the caffeine.

French’s Yellow Mustard – Conditions to avoid: heat, freezing, sunlight, moisture although it didn’t state the reasons why. The latter two obviously is to keep it from spoiling, but the former two makes me wonder.

What did I learn from all of this?  I’ve learned that Google (and other search engines) and the internet itself provide us with a vast amount of information, and a great way to kill some time on boring evenings.

As I mentioned in the very beginning, this post is more about the random factoids I have found on the internet then trying to convey the newest science news or interest scientific facts. As such, probably not very fitted for this blog.

Most of the information bears absolutely no significance to our daily life (considering how many of the assumptions are impossible in real life), but this has been a great adventure in searching for information relating to my random thoughts and has been a great time waster for me and hopefully for you too.

Fireflies are bioluminescent and chemically produce their own light from the abdomen’s“latern” organ. When researchers examined the structure of firefly laterns under a scanning electron microscope (SEM) they saw the abdomen cuticle consists of scales arranged in a jagged pattern. This misfit between scales produces a sharp edge that contributes to light scattering (i.e. overall light extraction) .

(a) Firefly Photuris sp. that was inspiration for this research (b) jagged scales viewed under the SEM (Bay et al 2013a)

“We refer to the edge structures as having a factory roof shape,” said Annick Bay, the paper’s lead author and a Ph.D. student at the University of Namur in Belgium, in a public release. “The tips of the scales protrude and have a tilted slope, like a factory roof.”

Light travels more slowly in the firefly cuticle than through air. This mismatch means some of the light produced from the firefly is reflected back into the lantern making the firefly less bright than they could be. But the researchers found the surface pattern the fireflies’ cuticles can help minimize internal reflections, allowing more light to escape (i.e. brighter fireflies).

Low light extraction efficiency occurs when there’s total internal reflection. The structure of the surface can be modified to increase light extraction efficiencies. The surface of GaN LEDs is typically modified by adding roughness or nanostructures to form a graded refractive index on the surface.

The new LED consists of a layer of light-sensitive material on top of a standard GaN LED. Sections of the light-sensitive layer are then exposed to a laser, creating the factory-roof structure. Since light travels even slower in the standard GaN LEDs than the firefly, the dimensions of the protrusions on the LED surface were optimized (height and width of 5 micrometers) to improve the amount of light that can be extracted from the LED. Researchers were surprised the micrometer sized protrusions were so effective in improving light extraction efficiency because convention optimization methods are based on protrusions in the submicron scale.

The researchers performed a series of experiments with coated (light-sensitive layer) and patterned (factory-roof like protrusions) and found:

1. A coated pattered LED was 54% more efficient than a bare LED
2. A coated patterned LED was 33% more efficient than a coated LED
3. A coated LED was 16% more efficient than a bare LED

While the patterned surface definitely improves the light extraction from LEDs, researchers believe the light-sensitive coating alone already gives a slight improvement because of the gradual transition in how quickly light travels from the LED to the air, minimizing the total internal reflection.

The technique is promising according to the researchers because of its simplicity and scalability, allowing any protrusion size to be made on a precise area of a large surface.
–
Bay, A., André, N., Sarrazin, M., Belarouci, A., Aimez, V., Francis, L., & Vigneron, J. (2013). Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes Optics Express, 21 (S1) DOI: 10.1364/OE.21.00A179

Bay, A., Cloetens, P., Suhonen, H., & Vigneron, J. (2013). Improved light extraction in the bioluminescent lantern of a Photuris firefly (Lampyridae) Optics Express, 21 (1) DOI: 10.1364/OE.21.000764\

Featured image source: Animal Planet

Researchers from Seoul National University and Kyung Hee University in Korea have developed a QR-code made from a polymer device that can be used for preventing drug counterfeiting. They describe their device in a recent issue of Advanced Materials.

Information or data like drug ingredients and expiration dates can be stored on QR-coded devices. Such on-dose authentication (ODA) technology is useful for drug identification, monitoring, and preventing drug counterfeiting. More importantly, these devices can be used to prevent wrong or expired ingredients from being used when drugs are delivered to repackaging companies or distributors in either raw or bulk forms. A typical smartphone with a QR Code reader application can be used to scan the code and authenticate the drug by determining its formulation.

Current anti-counterfeiting measures include printed marks or radio frequency optical tags but these can be imitated, and are insufficient to authenticate ingredients. The researchers describe their QR-coded device as a microtaggant, is microscopic and traceable particle that’s added to the drug for authentication. The microtaggant is included inside an individual tablet/capsule the during drug formation process (more about its biocompatibility later). Its small micrometer size means it cannot be easily copied or replaced with fake ones according to researchers.

The researchers encoded polymer microtaggant is made using an optofluidic maskless lithography system, consisting of a microfluidic device and an optical lithography system. A patterned UV light is projected onto the microfluidic channel which contains a photocurable polymer solution (poly(ethylene glycol) dimethacrylate). A fluorescent acrylic monomer (methacryloxyethyl thiocarbamoyl rhodamine B) was also added to the polymer solution so that the QR Code pattern has a vivid red colour (stands out from the background when a digital detector is used).

The researchers report that up to 7089 characters can be encoded in a single QR Code. The types of data that can be stored include: binary, numeric only, alphanumeric, multiple languages. To test their microtaggant, the researchers placed 10 microtaggants inside a single drug capsule. They broke open capsule dissolved the drug power in water, washing the microtaggants. The microtaggants were placed under a fluorescence microscope and decoded by reading the microscope image with a smartphone (the process is shown in the image below). The name of the researches’ lab, along with the lot number, production and expiration dates were all identified from the image of the QR Code.

Source: Han et al. 2012

As for biocompatibility (since the microtaggant is meant to be swallowed with the capsule): the polymer solution itself has been reported to be biocompatible. If anything, it seems the fluorescent dye is the more important concern. The researchers assume that if a single capsule contains 10 microtaggants, and a person takes 3 capsules daily then he/she will ingest about 220 micrograms of fluorescent dye in a year. This is considerably lower than the LD50 (887 milligram per kilogram in mouse), according to the team.

From this paper it sounds like the QR-coded microtaggant is good approach for preventing drug counterfeiting. Assuming that manufacturers and distributors will all have access to the fluorescent microscopes needed to verify the code, the decoding process seems quick and straight forward enough to be feasible. But to me it seems like a big and potentially challenging step would be to ensure/convince consumers that drugs containing such microtaggants can be safety ingested and safer to than current anti-counterfeiting alternatives.

—
Han, S., Bae, H., Kim, J., Shin, S., Choi, S., Lee, S., Kwon, S., & Park, W. (2012). Lithographically Encoded Polymer Microtaggant Using High-Capacity and Error-Correctable QR Code for Anti-Counterfeiting of Drugs Advanced Materials, 24 (44), 5924-5929 DOI: 10.1002/adma.201201486

Source: http://www.123rf.com

As you get ready to celebrate the New Year, you’ve likely come across articles about different food ‘cures’ that can prevent or reduce alcohol hangovers. Aside from anecdotic ‘evidence’ that greasy foods or burn toast are remedies for hangover symptoms, is there scientific evidence that certain foods to effectively prevent or treat hangovers?

Different media outlets have recently picked up a press release about a 2009 study (open access) evaluating the effectiveness of asparagus on easing of alcohol hangovers. What I found interesting about this story wasn’t just the findings (spoiler alert—asparagus is a potential candidate for treating hangovers).

After a little searching through some journal databases, I learned that our knowledge on the pathology of alcohol hangover is incomplete according to Penning et al. (2011). Lee et al. (2012), Vesster (2008) both point out that numerous hangover ‘cures’ are available yet few have been scientifically studied and none are significant in preventing or relieving hangovers.

In fact it seems to me a lot of ‘cures’ just treat specific symptoms rather than the cause of hangovers. We know that excessive alcohol consumption can lead to feeling tired, headaches, weakness, nausea, thirst, concentration problems, and people experience a variety of symptoms and severity. So foods like bacon, eggs, and toast replenish blood sugar and/or electrolytes to rehydrate the body (Anderson et al. 2010).

So what did we learn from the asparagus study by Kim et al. (2009)? The researchers evaluated the effects of extracts from asparagus shoots and leaves on the physiological functions in human liver cells. They also evaluated if the extracts affect the concentration of the ADH and ALDH enzymes (key enzymes for alcohol metabolism) in rat liver cells.

It turns out the presence of the asparagus extracts does promote higher ADH and ALDH activities. The researchers conclude that asparagus extracts have strong antioxidant activity and is effective in stimulating the enzymes needed to metabolize ethanol. So asparagus is a potential candidate for protecting the liver since rapid and efficient removal of ethanol is important for detoxification (and easing hangover symptoms).

As far I can tell, there have not been any follow up studies with actual people to evaluate the effectiveness of consuming asparagus for preventing or treating alcohol hangovers. But Kim et al. (2009) also showed in their study that asparagus is a good nutritional source of inorganic minerals like calcium and potassium, and other organic nutrients like protein. And even more interestingly they found asparagus leaves contain several times the nutrients as the asparagus shoots does.

While I’m not suggesting you should drink until you get a hangover but if you end up with one, maybe it’s worth giving asparagus a shot? At the very least it’s a nutritious vegetable to start your new year with.

—
Anderson, K. (2010). Hangover, How to Change Your Drinking: A Harm Reduction Guide to Alcohol (pp.180-191).

Kim, B.-Y., Cui, Z.-G. Lee, S.-R. Kim, S.-J., Kang, H.-K., Lee, Y.-K. & Park, D.-B. (2009). Effects of Asparagus officinalis Extracts on Liver Cell Toxicity and Ethanol Metabolism Journal of Food Science: 10.1111/j.1750-3841.2009.01263.x

Lee, H., Isse, T., Kawamoto, T., Woo, H., Kim, A., Park, J., & Yang, M. (2012). Effects and Action Mechanisms of Korean Pear ( ) on Alcohol Detoxification Phytotherapy Research, 26 (11), 1753-1758 DOI: 10.1002/ptr.4630

Verster, J. (2008). The alcohol hangover-a puzzling phenomenon Alcohol and Alcoholism, 43 (2), 124-126 DOI: 10.1093/alcalc/agm163

Penning, R. (2011). Caffeinated Drinks, Alcohol Consumption, and Hangover Severity The Open Neuropsychopharmacology Journal, 4 (1), 36-39 DOI: 10.2174/1876523801104010036

B.-Y. KIM, Z.-G. CUI, S.-R. LEE, S.-J. KIM, H.-K. KANG, Y.-K. LEE, & D.-B. PARK (2009). Effects of Asparagus officinalis Extracts on Liver Cell Toxicity and Ethanol Metabolism JOURNAL OF FOOD SCIENCE : 10.1111/j.1750-3841.2009.01263.x

An image of the polymer composite and a schematic it the composite being stretched and its photoluminescence properties. (X. Jin et al. 2012)

You can usually tell when a material is about to fail, you might see sagging, cracks, dents, holes, etc. But sometimes materials can fail suddenly—without warning— this known as catastrophic failures.

Researchers in Germany report for the first time in a recent issue of Advanced Materials, a method of detecting the amount of deformation a material undergoes based on its colour intensity (light emission). The researchers made a polymer composite material containing micrometer sized zinc oxide particles that shows photoluminescence properties when shone with ultraviolet light.

Photoluminescence occurs when an external energy source (i.e. electromagnetic radiation like ultraviolet in this case) is absorbed for an atom/molecule and produces photon emissions (i.e. light). This is a composite material is made of a polymer known as poly(dimethylsiloxane) that’s dispersed with the zinc oxide particles. The zinc oxide particles are filler materials but have the added bonus of strengthening the polymer. They were also chosen to be the filler material because they often show blue-green light emissions at room temperature.

The polymer composite was pulled at constant speed until it broke, and UV light was continuous shone at the centre of composite during the pulling. The amount of light emitted by the composite was recorded relative to the amount of UV light emitted. The researchers report that the amount of light emission from the composite relative to UV emission (input energy source) decreases as the material is stretched. They explain that the volume of material being excited by the UV light is reduced as the material stretched, increasing the amount of UV radiation reaching the surface.

They mention that the light emission of zinc oxide is related to the amount of surface defects. But don’t go into further details about the actual density of surface defects and/or how the defect density in the sample changes as the composite is stretched (although the defect density typically increases).

According to the results, the composite material has a maximum tensile strength of about 1.3 MPa. But the researchers also report some of the fillers were partially separated from polymer matrix, broken into individual whiskers, suggesting that delamination influenced the material strength.

Regardless of the strength of the composite material, the researchers believe that this material has potential to be used in future engineering applications because the internal damage can be detected by photoluminescence. While sensing the stress of a material is a novel concept, the tensile strength of the polymer composite is only about 1.3 MPa—
which is pretty low considering cellophane film ranges from 50-120 MPa [2]. So I think the material’s strength needs to be addressed before engineering applications can truly be considered.

—

[1] Jin, X., Götz, M., Wille, S., Mishra, Y., Adelung, R., & Zollfrank, C. (2012). A Novel Concept for Self-Reporting Materials: Stress Sensitive Photoluminescence in ZnO Tetrapod Filled Elastomers Advanced Materials DOI: 10.1002/adma.201203849

[2] “Polymer Chemistry” 21 July, 2000. Retrieved from http://faculty.uscupstate.edu/llever/Polymer%20Resources/Mechanical.htm

This is where researchers like the University of Windsor’s Dr. Sreekanta Das can help. Dr. Das and his research team have been developing a model based on the Paris Equation to estimate how long a cracked pipeline can be used  in service without causing any dangers of leaking or bursting.

In the school context, the Paris Equation represents a very simple situation—you’re given various values and constants and it’s simply just “plug-and-play”. The only challenge to getting the correct fatigue life estimate is making sure all of the numbers are entered in the same units of measurement.

But using this equation correctly to predict real-life situations (like the fatigue life of an oil/gas pipeline) is more complicated that you may think. “[The Paris Equation] has lots of parameters that will depend on specific applications, materials, load history, and crack shape,” says Das. “It’s your job to figure the parameters to fit into the equation.”

Here’s a link to my latest article in EPCM World where I spoke to Dr. Das about his model on assessing the fatigue life of pipelines.

A photo of  the Trans-Alaska Pipeline system. (Source: Wikipedia)