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Tuesday, 15 November 2016

High spatial dynamics-photoluminescence imaging reveals the metallurgy of the earliest lost-wax cast object

M. Thoury, B. Mille, T. Séverin-Fabiani, L. Robbiola, M. Réfrégiers, J-F Jarrige & L. Bertrand

Photoluminescence spectroscopy is a key method to monitor defects in semiconductors from nanophotonics to solar cell systems. Paradoxically, its great sensitivity to small variations of local environment becomes a handicap for heterogeneous systems, such as are encountered in environmental, medical, ancient materials sciences and engineering. Here we demonstrate that a novel full-field photoluminescence imaging approach allows accessing the spatial distribution of crystal defect fluctuations at the crystallite level across centimetre-wide fields of view. This capacity is illustrated in archaeology and material sciences. The coexistence of two hitherto indistinguishable non-stoichiometric cuprous oxide phases is revealed in a 6,000-year-old amulet from Mehrgarh (Baluchistan, Pakistan), identified as the oldest known artefact made by lost-wax casting and providing a better understanding of this fundamental invention. Low-concentration crystal defect fluctuations are readily mapped within ZnO nanowires. High spatial dynamics-photoluminescence imaging holds great promise for the characterization of bulk heterogeneous systems across multiple disciplines.


Jaydeep said...

Dear Nirjhar,

This is an excellent new finding. I haven't had the time to go through the paper as yet unfortunately. But I was drawn attention to one peculiar aspect of this 'pendant' as the authors call it. It has been argued by one scholar who is a member of a yahoo group that this is an example of a spoked wheel.

We need to look more into it before confirmation. But this is indeed a very good suggestion. Certainly, if by 4000 BC, the Indus people could design such spoked rings, what could possibly have prevented them from designing a spoked wheel ?

Nirjhar007 said...

Welcome :). And yes those amulets are an indirect proof that the Spoked wheels were known . And AFAIK spoked wheels were also absent in symbolism in archaeological cultures prior to that period .

The six spoked wheel is also found as a popular symbolism throughout the civilization .

See for example here-

A scholar friend informs me that :
the famous hymn RV I.164, st.12: pañcapādaṃ pitaraṃ dvādaśākṛtiṃ diva āhuḥ pare ardhe purīṣiṇam |
atheme anya upare vicakṣaṇaṃ saptacakre ṣaḷara āhurarpitam || "They speak of the father [=the Moon] with five feet [=the seasons] and twelve forms [=the months], the overflowing one in the upper half of heaven.
But these others speak of the far-gazing one [=the Sun] in the nearer (half) fixed on (the chariot) with seven wheels [=the Sun, Moon, and visible planets] and six spokes [=the seasons, in a different reckoning]."

the stanza is repeated in AV and Prashan Upanishad (I.11), about which Shankara's commentary says: ṣaḍare ṣaḍṛtumaty, also identiifying the six spokes with the six ṛtu, seasons. And it seems that the symbol of Rituchakra is still known in India..

And out of many other interesting parallelism this late one is also there where we see presence of amulets again :
''The figure holding the broken wheel in plate C is more tentatively thought to be Taranis, the solar or thunder "wheel-god" named by Lucian and represented in a number of Iron Age images; there are also many wheels that seem to have been amulets.''