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January 17, 2017

I Can See Clearly Now

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An abandoned house or factory building is often associated with windows boarded up with plywood. Over time, glass windows can break due to neglect or vandalism, and the plywood boarding helps prevent rain, snow, and debris from entering the building. The appearance of plywood boarding, however, draws attention to the abandoned nature of the building, and can shield illicit activity inside the building from the eyes of neighbors and law enforcement.

Several communities have converted to polycarbonate sheets instead of plywood. Polycarbonate is a transparent plastic that is much tougher than glass, which will help against breakage, yet has the same appearance as glass, effectively improving the curb appeal and inhibiting illegal activities inside the property. The technique of using polycarbonate sheets is called ‘clear boarding,’ and is being mandated by Fannie Mae on its vacant properties. Polycarbonate is used for bullet-resistant glass found in banks and armored cars, as well as windows for airplanes, motorcycles, helicopters, and some screens for electronics. Polycarbonates were first found in the late 1800s, but finally commercialized in the 1950s. 

Two potential downsides to clear boarding are the cost, which can be upwards of 6 times as much as plywood, and challenges with entry by firefighters. The tough nature of polycarbonate requires firefighting personnel to cut through the polycarbonate enclosures with saws, rather than breaking them with axes. Proponents of clear boarding suggest that the reduced chance of property damage and illegal activities will offset the cost and reduce the likelihood of arson or accidental fires.

Posted by CatherineCerasuolo
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January 16, 2017

Evolution of Drug Resistant Bacteria

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Recently there has been increasing concern with antibiotic resistant bacteria.  To a large extent, this increase can be attributed to over-subscription of antibiotics leading to evolved resistance of the bacteria.  At its worst, this heightened use of antibiotics has led to organisms such as Methicillin-resistant Staphylococcus aureus (MRSA), also known as a “super bug”.  The real issue behind this bug is that it can be present in hospitals and healthcare facilities where the most vulnerable population are present.  However, visually demonstrating this acquired resistance is not straightforward and therefore the message of being more judicious with antibiotics (and fully completing the prescribed course) can get lost. 

Researchers at Harvard University released a compelling video that allows one to watch the acquired resistance to antibiotics visually:

The Evolution of Bacteria on a "Mega-Plate" Petri Dish from Harvard Medical School on Vimeo.

Posted by CatherineCerasuolo
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January 4, 2017

Rheology's Role in Dysphagia

Ever have a lump in your throat? You may have dysphagia, a medical condition whereby the patient has difficulty swallowing solids and liquids. There are multiple causes for dysphagia, ranging from gastroesophageal reflux to esophageal cancer. If not treated, pulmonary aspiration could occur when liquids enter the lungs by accident. Treatment of dysphagia depends on the source of the condition, but may be as simple as modifying swallowing behavior and changing diet, or it may require surgery for more complicated conditions. 

Artificial Throat Monitors Flow Behavior of Food

We have often discussed the rheology, or flow behavior, of food products on our web site, and how it relates to taste and consumer perception. Rheology of food can also play a role in dysphagia.  Thicker liquids may be easier to swallow for dysphagia patients. To test this theory, researchers at the University of Cambridge, headed by Professor Malcolm Mackley, constructed an artificial throat to monitor flow behavior of liquids of varying viscosities when ‘swallowed’ by the throat.

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Dialysis tubing was used to model the throat, with rollers and counterweights representing the tongue. Optical access allowed the monitoring of the residence time of a bolus of fluid makes its way past the tongue and epiglottis. 

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Various fluids containing common thickeners used in the food industry (xantham gum, nutilis) were investigated. Shear and extensional rheometry were performed, since both these modes of deformation would be present in the throat, and provided key viscoelastic properties for the fluids.

The authors concluded that the viscoelastic properties of the test fluids played a role in the amount of time it took for the fluid to travel from the epiglottis to the airway, which could affect aspiration and patient comfort. 

Posted by CatherineCerasuolo
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December 28, 2016

Trainable Skin Cells

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Our pets may be difficult to train, but researchers at the University of Toronto have developed a peptide-based hydrogel system that helps encourage skin cells to crawl towards each other, leading to a more rapid closure on chronic wounds commonly found in diabetic patients. 

At left, skin cells without the research team’s peptide-hydrogel treatment. In the middle, cells treated with a low dose. At right, cells treated with a high dose. Skin cells migrate together fastest with a high dose of the peptide-hydrogel material (photo from Radisic Lab)

With their hydrogel system, wounds closed in less than 2 weeks. The peptide-hydrogel system promotes survival of the cells, and gives the cells a substrate to crawl over to help with wound closure.

I wonder if it works on dogs?

Posted by CatherineCerasuolo
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December 20, 2016

Caramel: A Baker’s Excuse for Over-Cooking

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As the holiday baking season approaches, we are naturally thinking about caramel. At CPG, we have tested caramels and other food products in order to determine why some of these products have better ‘mouth-feel’ than others based on rheological assessment, a science sometimes termed ‘psychorheology’.

Chemistry of Caramel

The discussion today, however, has to do with the chemistry of caramel. Caramel is the result of a decomposition reaction of sucrose (also known as table sugar) when it is heated to its decomposition temperature, between 170-186 C. Sucrose is a disaccharide made up of glucose and fructose. When it decomposes, water is released through a condensation reaction, along with glucose initially. Additional polymerization and isomerization then occurs, resulting in multiple high molecular weight compounds, as well as lower molecular weight compounds.

The lower molecular weight compounds are more volatile, and generate the characteristic aroma associated with caramels, including ethyl acetate (fruity/pineapple), furans (almonds), diacetyl (butter flavor), and maltols (toasted bread).

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Sucrose, on the other hand, has a very mild odor, often not detectable due to its low volatility. The distinctive caramel smell is familiar to many polymer analysts who either deliberately or inadvertently decompose polysaccharides, generating many of the same compounds found in caramel.

The chemical reactions that occur at this stage are not really well known, even to this day. It is known that dimerization occurs, whereby two sugars reaction to form a single molecule containing three cyclical structures and a dianhydride. These structures are then believed to undergo hydrolysis reactions that product a compound called caramelan (C12H12O9), caramelen (C36H18O24) and. caramelin (C24H26O13), depending on the amount of water lost. These compounds form particles that have color centers believed to result in the color changes in caramel.

In addition to these reactions, free radicals are produced, which play a role in the tacky nature of caramels due to enhanced van der Waal’s interactions.

So although a great deal is not known about the chemical reactions in caramel, we can all perform our own enthusiastic home study on this wonderful cooking mistake.

Posted by CatherineCerasuolo
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December 12, 2016

FDA Workshop on Refurbishing of Medical Devices

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If you were not able to attend the FDA workshop on "Refurbishing, Reconditioning, Rebuilding, Remarketing, Remanufacturing, and Servicing of Medical Devices Performed by Third-Party Entities and Original Equipment Manufacturers" last October, the video and transcript are available here

CPG President Stephen Spiegelberg speaks during October 28, Part 4.

Posted by CatherineCerasuolo
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December 5, 2016

Nano Diet for Silkworms

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Silk is recognized as an expensive, luxury textile material, having been used for several thousand years for fine fabrics, tapestries, clothing, and runs. Silk is a protein-based fiber produced by the larvae-form of several insects, most notably silkworms, but also by spiders, bees, beetles, and other insects. The mechanical properties of silk can rival synthetic fibers such as Kevlar. CPG co-founder Gareth McKinley, a professor at MIT, is doing research on spider silk in an effort to make military armor lighter and more flexible. CPG researchers McKinley and Braithwaite also have experience developing artificial spider silk.

Researchers from China discovered that feeding silk works carbon nanotubes permitted the natural production of reinforced silk fibers.  A portion of the nanotubes fed to the silkworms was incorporated into the silk fibers, which modified the structural conformation of the silk fibroin, increasing the elongation at break and toughness.

Contact CPG for more information on custom chemical formulations and electrospinning.

Posted by CatherineCerasuolo
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