Dear Gabriele,I should give you more context. About 20 years ago, archaeologists began finding remnants of starchy foods on ancient food processing tools. At first nobody thought it was a real result, but then more and more people began finding starch on stone tools and pottery in many different countries and environments. Having such direct evidence of the foods used in the past, including foods such as root crops that do not have easily preserved hard parts, has been a very important advance for understanding the transition from hunting and gathering to agriculture. Starch has been found on tools up to 200,000 years in age. It is incredibly stable, but it is often hard to identify the species because it is variable within species, and has not many obvious distinguishing features, and is also often in a partly degraded condition. If your laser ablation approach could somehow generate a species-specific signature for identifying starch, it would be revolutionary for archaeology, because until now, identification is the key problem limiting the interpretation of ancient starch remains.To find and see the starch, is very simple: we can use a micropipette and water to remove the starch from cracks and holes in the surfaces of stone tools, and from residues stuck on the insides of pots. If 80 ul is removed from a particular point on a tool, 8 ul can be used for one slide, filling the space under a cover slip, and within that 8 ul there might be anything from 0 to 100s of starch granules (if clumps of starch are present), as well as fragments of plant tissue, and a lot of dirt particles. Removing a coverslip to transfer individual starch granules to another place for analysis would be very tricky. With light microscopy and cross-polarised light, we can recognise starch by the laminated internal structure of the granule, shape, and a characteristic birefringence - which produces a so-called Maltese cross effect. Sometimes we can identify the species, but often not. There is a real need for specialists in other fields to look at ancient starch, as it is an almost completely unexplored subject from physical and natural science perspectives. I am interested in the historical implications of the material, but of course the challenge of analysing this newly-discovered phenomenon could have many unexpected outcomes for the natural and physical sciences, for methods, and for related subject fields (e.g. for understanding the ultimate fate of photosynthetic carbon in the physical environment).Best regards, P.
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
Nanoparticle project via Pulsed Laser Ablation in Liquid
Research Cooperative
@chief-admin
14 years ago
226 posts
Gabriele Cristoforetti
@gabriele-cristoforetti
14 years ago
4 posts
Dear Peter, you want to fix starches particles of a few nanometers dimensions on a grid and then cover them with a glass ?
Research Cooperative
@chief-admin
14 years ago
226 posts
Dear Gabriele,I have seen that confocal microscopy can be done as an adjunct to normal light microscopy for material under a glass cover slip. This is convenient for ancient starch research because there are typically just a few individual starch granules on a single slide. These have to be located manually and then given a grid reference so that they can be located again for confocal laser microscopy. Are your techniques compatible with a glass cover slip (or cover of some other kind of optically transparent material?)Thanks again, P.
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
Gabriele Cristoforetti
@gabriele-cristoforetti
14 years ago
4 posts
If you are interested in measuring chemical contaminants (silica, metals, ecc.), we can look at the spectroscopic signal of the laser-induced plasma. For understanding the structure is much more complex; maybe we could try by vaporizing the material at low laser fluences and observing the eroded surface via confocal microscopy (which we have in our laboratory). It is not necessary to work in a liquid enviroenment; we can ablate in air.Gabriele
Research Cooperative
@chief-admin
14 years ago
226 posts
Dear Gabriele,Thanks for the explanation. Your interest is in what is released and produced when a target object is ablated in a liquid. My question is whether the laser can be used to degrade in a controlled manner the surface of the object (a starch granule for example) in order to reveal characteristics of the object. These might be revealed by looking at the eroded surface (e.g. by confocal laser microscopy), and also by looking at the products formed in the surrounding solution. Starch is primarily composed of long and more-or-less branched polysaccharide chains, but also contains fats and proteins, and in archaeological contexts may be partially-mineralised with silica and other soil components. Playing with controlled, experimental combinations of silica, starch and starch-silica mixtures might be an interesting starting point. I work in an anthropology museum, so can only speculate about these materials and methods.Cheers, P.
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
Gabriele Cristoforetti
@gabriele-cristoforetti
14 years ago
4 posts
Dear Peter,I have not well understood the problem you propose. The method that I described allows to produce nanoparticles by focusing a laser pulse on the surface of a target submerged in a liquid. The energy of the pulse results in the ablation of the target, forms a plasma which cools in the liquid environment producing the nanoparticles. I have not understand what you suggested with the starch granule. For what concerns the gel, I suppose that a part of the laser is absorbed in the gel itself. Nanoparticles would probably be formed by chemical elements composing the target and the polymers (carbon, nitrogen, oxygen..).What you think ?
Research Cooperative
@chief-admin
14 years ago
226 posts
I wonder what happens when the liquid is a gel composed of hydrated polymers? I'm thinking of carbohydrates.....Could the method be used to highlight the internal structure of semi-crystalloid substance like starch, in a starch granule? This could be useful for archaeologists wishing to identify individual starch granules with diameters of 10 to 50 nm.P.
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
--
Peter J. Matthews, Chief Admin.,
The Research Cooperative,
Auckland & Kyoto.
Contact: researchcooperative [at] gmail [dot] com
Gabriele Cristoforetti
@gabriele-cristoforetti
14 years ago
4 posts
Dear all,
I began working in the production of nanoparticles via Pulsed Laser Ablation in liquid environment. The method seems very interesting because NPs are "pure", devoid of surfactant agents and chemical precursors. I am interested in joining projects related to such a matter.
Gabriele
updated by @gabriele-cristoforetti: 21/06/17 01:16:09PM
I began working in the production of nanoparticles via Pulsed Laser Ablation in liquid environment. The method seems very interesting because NPs are "pure", devoid of surfactant agents and chemical precursors. I am interested in joining projects related to such a matter.
Gabriele
updated by @gabriele-cristoforetti: 21/06/17 01:16:09PM