Tuesday, September 09, 2014

Why supporting wine bottles by the neck for long-term aging is a bad idea

A relatively recent trend in short-term wine storage are cute holders that use the neck of the bottle as the holding point and counter-balance themselves against the weight of the lower portion of the bottle.  Some hobbyists have even taken to crafting racks like this themselves (not unlike riddling racks).  One well-built example (borrowed from Reddit user “ILovePooch”) is shown here:

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This is a nice design, very attractive, with a wide base that should prevent any tipping of the rack, and good points on the top that can be wall-anchored.  However, there are concerns about using this for long-term bottle aging.

The short explanation: This is a bad idea for long-term storage. The fundamental reason for this are inherent flaws in the glass that may propagate in high-stress regions (i.e. in the neck and shoulder, in this case) when exposed to wine.

The long explanation: The fracture mechanics of glass are dominated by largest flaw in a stressed region...this is why scoring and breaking works on glass and ceramics, but not on metals. In materials science, we quantify this by calculating a Weibull modulus by testing many hundreds of test specimens. In general, a single pore or surface scratch will not be enough to allow a relatively thick bottle to fracture under a constant minor load. Hence, this design is OK for the short term.

Over time, though, a small (read: tens of microns/< 0.001 inches) crack exposed to an aqueous environment - especially an acidic environment - will grow. The mechanism for this is still debated, but it is usually thought that the atoms at a sharp crack tip in a ceramic tend to react quickly with the water. This makes sense to some extent; the atoms at the crack tip are in a state of triaxial tension when the crack is under a tensile load, meaning they are "higher energy" and more likely to react. Over months, large starting cracks could propagate quickly and cause failure of the bottle. Over years, even small flaws could react with the aqueous environment.

The worst part is that this is not a sure thing. It is a purely statistical process. It may happen to thin-walled bottles, thick-walled bottles, expensive bottles, or bottles of two-buck-chuck. It may never happen if one happens to buy bottles without significant flaws facing the wine (as external (air-facing) and internal cracks in a ceramic are very unlikely to grow under a constant applied stress). For long-term cellaring, it really will be playing the odds.

Freely available further reading: Cicotti, M., “Stress-corrosion mechanisms in silicate glasses,” http://arxiv.org/abs/0901.2809

Thursday, March 20, 2014

Zinc phosphate “arrowheads” in the SEM

Imaging some zinc that had been soaked in a phosphate buffered saline-based solution last week, I ran across lots of little zinc phosphate crystals.  Two really stood out, and are shaped almost exactly like arrowheads.  Far out!

Zinc phosphate arrowhead (1)

Zinc phosphate arrowhead (2)

The instrument used was Michigan Tech’s Hitachi S-4700 FE-SEM.  Both of these images were captured in “low magnification” mode because the salt crystals are so darn big.  They measure a little less than 0.1 mm, and so they are a little smaller than you can see with the naked eye.

Thursday, March 13, 2014

ResearchGate introduces new “open review” feature

ResearchGate, a peer networking site for research professionals, is introducing an "open review" feature that allows users to comment on published studies and characterize them as "reproducible" or "non-reproducible," among other things. This could evolve into a very important tool for disseminating post-publication validation studies, and would be a welcome alternative to the current expensive, centralized validation efforts.

image

The statement that “peer review isn’t working” might be a little harsh, but there is at least anecdotal evidence to back it up. 

They seem to zero in on the current controversy surrounding the article “Stiumuls-triggered fate conversion of somatic cells into pluripotency,” using that as an example publication.  It is marked “non-reproducible” on the announcement page:

image

There are still some questions to be answered here. 

Could there be opportunity for abuse of this systems?  

Will it be an issue for novice ResearchGate users, who might tend to clutter the "reviews" area with unrelated questions and criticisms? 

The latter seems more likely, as ResearchGate does not easily allow for anonymity, and the “questions” feature is already cluttered with easily answered questions from undergraduate and graduate students.  Hopefully the helpful “open reviews” on ResearchGate will not be in the minority, as is currently the case with the questions feature.

Monday, June 17, 2013

Degradable zinc stent research featured in the June 2013 MRS Bulletin

Exciting news!  Our research on bioabsorbable zinc stents has been featured in the June 2013 edition of the Materials Research Society (MRS) Bulletin.  The article discusses our recent article in Advanced Materials titled “Zinc Exhibits Ideal Physiological Corrosion Behavior for Bioabsorbable Stents” (read it on Scribd).  They interview my advisor, Prof. Drelich, about our research program and discovery.

Bio Focus: Is zinc the perfect material for bioabsorbable stents?

I believe this article is free-to-read, but I could be wrong about that.  Feel free to contact me if you would like a copy!

Monday, April 29, 2013

New results in the Journal of the American Ceramic Society on rehydroxylation ceramic dating (2/2)

This post, second in a series of two (click for part one), discusses our communication to the Journal of the American Ceramic Society, entitled “Effect of humidity instability on rehydroxylation in fired clay ceramics” by J. Drelich, P. K. Bowen, and T. J. Scarlett, which appeared in vol. 96, issue 4, pages 1047-1050.  The abstract is as follows:

Several samples of the XIX-century Davenport pottery and XX-century structural masonry were reheated at 500°C and then exposed to a humid gas of controlled relative humidity. Changes in the sample masses were recorded in response to both systematic and transient step changes in humidity. In addition, a reheated masonry sample underwent a sequence of soaking and drying and hundreds of hours of interactions with humid air in between these treatments to examine long-term effects of extreme humidity fluctuations. All experimental results indicate that instantaneous humidity and the sample's hygral history have a negligible effect on the long-term kinetics of mass gain. This important finding provides strong experimental support for the newly developed rehydroxylation (RHX) ceramic dating technique by proving that humidity affects physically bonded water in the ceramics, but has a negligible effect on chemically bonded water.

doi: 10.1111/jace.12262
Preprints archived at ResearchGate and Scribd

In plain English: we messed with the humidity during rehydroxylation of fired clay ceramics, and it had no effect on the kinetics of mass gain.  Therefore, there is no long-term effect on the rehydroxylation (RHX) behavior that would skew projected dates.

It was stated in earlier work on RHX dating that humidity did not seem to have any serious effect on the performance of rehydroxylation ceramic dating, but definitive evidence was not provided.  This communication works to fill this void, and provides some definitive results for a certain sample type that shows that the original assertions were correct.  To prove this, the humidity was modulated both transiently (a brief burst of high humidity) and systematically (a change from low to high humidity partway through the test). 

In the first (transient) case, the slope of the time1/4 trendline was shown to be the same before and after the humidity was increased and again decreased, indicating that the rehydroxylation kinetics did not change.  Even when the sample was severely abused by soaking in water (i.e. raining) and being dried near the boiling point (i.e. baked in the sunshine), there were no indications that the long-term behavior experienced any changes (see image below).  This is good news!

Figure 3, 300dpi

The second (systematic) case showed the same thing: no changes in the trend were observed with a single jump in the humidity level.  This shows that a systematic change in humidity, like would be experienced season-to-season (such as winter-to-spring or monsoon-to-dry season), does not have an impact on the rate of water uptake.  (The same cannot be said for temperature, of course!)

Scribd preprint

Effect of Humidity Instability on Rehydroxylation in Fired Clay Ceramics by Patrick Bowen