Non-destructive X-ray scanning of archeological finds

Dating archeological finds has long required taking a bit of the artifact to find out how many years ago it lived or was made, and where it originated. But now, by adapting an off-the-shelf portable X-ray lab tool that analyzes the composition of chemicals, Prof. Yuval Goren of Tel Aviv University’s department of archeology and ancient Near Eastern civilizations can reveal hidden information about a tablet’s composition without damaging the precious ancient artifact.

The X-rays also reveal the soil and clay composition of a tablet or artifact, to help determine its precise origin. Based on X-ray fluorescence (XRF) spectrometry, Goren’s device can go much further. Over the years, he has collected extensive data through physical “destructive” sampling of artifacts. By comparing this data to readouts produced by the XRF device, he’s built a table of results so that he can now scan a tablet – touching the surface of it gently with the machine – and immediately assess its clay type and the geographical origin of its minerals. He says the tool can also be applied to coins, ancient plasters and glass, and can be used on site or in a lab, and plans to make this information widely available to other researchers.

Goren’s field intersects the worlds of geology, mineralogy and ancient technology as he tries to understand where ancient tablets and pots were made, based on the crystals and minerals found in these artifacts. “It’s become a big ethical question,” says Goren. “Many museums will not allow any more physical sampling of artifacts, and it’s especially problematic for small tablet fragments and stamps that cannot be broken in the process. I had to find another way to know what these artifacts were made of.”

In a recent study published in the Israel Exploration Journal, Goren and colleagues investigated a Late Bronze Age letter written in the Akkadian language, and found among the Ophel excavations in Jerusalem. Its style suggests that it is a rough contemporary tablet of the Amarna letters – written from officials throughout the Middle East to the Pharaohs in Egypt around 3,500 years ago.

Using his device, the TAU scientists were able to determine that the letter is made from raw materials typical to the Terra Rossa soils of the central hill country around Jerusalem. This determination helped confirm both the origin of the letter and possibly its sender.

“We believe this is a local product written by Jerusalem scribes, made with locally available soil. Found close to an acropolis, it is also likely that the letter fragment does in fact come from a king of Jerusalem,” the researchers reported, adding that it may well be an archival copy of a letter from King Abdi-Heba (a Jebusite king in Jerusalem) to the Pharaoh.

MARILYN AND THE NEURON

Marilyn Monroe, dead nearly four decades, is helping to conduct research on brain cell “firing rates.” Twelve patients involved in the study, recently published in the journal Nature, suffered from severe, treatment-resistant epilepsy and were awaiting neurosurgery at the UCLA Ronald Reagan Medical Center in Los Angeles to remove the brain tissue responsible for initiating seizures. The research, headed by Prof. Moran Cerf from the California Institute of Technology in Pasadena and including Tel Aviv Sourasky Medical Center neurosurgeon Prof. Itzhak Fried, demonstrates how our brains – which are constantly bombarded with images, noises and smells – can consciously select which stimuli to notice and which to ignore.

Fried said that to identify the precise region responsible for this, he implanted an array of 64 tiny electrodes around an area called the medial temporal lobe (MTL) and recorded from them constantly until a spontaneous seizure happened. This area, which includes the hippocampus and is associated with memory, is a frequent source of epileptic seizures. The volunteers, whose brains were wired up to a computer, enhanced one of two competing images of famous people or objects by changing firing rates in individual brain cells. In the experiment, the scientists flashed a series of 110 familiar images such as pictures of Marilyn Monroe or Michael Jackson in front of each of the patients and identified individual neurons that uniquely and reliably responded to one of the images; they selected four images for which they had found responsive neurons in different parts of a subject’s MTL. Then they showed the subject two images superimposed on each other. Each was 50 percent faded out.

The subjects were told to think about one of the images and enhance it. They were given 10 seconds, during which time the scientists ran the firing of the relevant neurons through a decoder. They fed the decoded information back into the superimposed images, fading the image whose neuron was firing more slowly and enhancing the image whose neuron was firing more quickly. Watching this on-line feedback, the subjects were able to make their targeted image completely visible and entirely eliminate the distracting image – in more than two-thirds of trials – and they learned to do so very quickly. Afterward, they reported that they had used different cognitive strategies.

Some tried to enhance the target image, while others tried to fade the distracting images.

Both had worked, but feedback on the computer screens was vital. When this “brainmachine interface” wasn’t provided, their success rates plummeted below one-third.

The research is very exciting, says neuroengineer John Donoghue of Brown University, “because it shows how we can now peer into the process of thinking at a level we have not been able to get at before.” Donoghue was responsible for the first successful transplantation of a chip into the motor cortex of a tetraplegic man, enabling him to move a computer cursor and manipulate a robotic arm with his mind.

The experiment shows how humans can use thinking to alter perception of competing visual images, says Cerf. “The environment offers some reality,” he says, “but your own brain can shape it and override it with its internal deliberations.”

In the future, he adds, this type of brain-machine interface may be exploited to read some thoughts of “locked-in” patients – people who are awake but cannot communicate because they are paralyzed – by monitoring the firing of neurons which respond to concepts such as “water” or “mother” – yet that’s still science fiction, he cautions.

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