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Posts Tagged ‘Physics’

Archeology,Physics

A match made in Megiddo

How the chemistry between archaeology and physics researchers led to groundbreaking discoveries about biblical history

Sometimes when you’ve stopped looking for a solution is exactly when it pops up. Israel Finkelstein, Jacob M. Alkow Professor of the Archaeology of Israel in the Bronze and Iron Ages, Sonia and Marco Nadler Institute of Archaeology, discovered a very interesting finding in 1998, at the archaeological excavation of Megiddo. He noticed a dig participant who did not quite fit the profile of a typical university undergraduate. 

“I sniffed around and learned that this particular student was actually a TAU professor flying under the radar. He turned out to be a very important ‘find,’” smiles Finkelstein. That student, incumbent of the Wolfson Chair in Experimental Physics Eli Piasetzky, Raymond and Beverly Sackler Faculty of Exact Sciences, was pursuing a degree in archaeology. Prof. Finkelstein pulled him aside to talk, and so began a research partnership that is still active two decades later.  

When were early Biblical texts written?

The archaeological issue of the day was mapping the chronology of the Iron Age in ancient Israel. Finkelstein challenged Piasetzky to improve the dating of remains from biblical times by using the radiocarbon method. The findings, published in professional and lay publications worldwide, rendered a new timeline of ancient Israel with lasting ramifications for biblical studies.

“Until then, the dating of texts was based on Biblical considerations,” explains Prof. Finkelstein, adding, “You can say that Biblical history was the path of the researchers, and archeology was used as a tool to prove the Bible stories were true.” He said. His article caused an uproar among researchers around the world, and he realized that he needed a more accurate dating tool and a talented mathematician to help him. Prof. Finkelstein presented his friend with a challenge – to accurately date the findings discovered in the excavations and to prove his claims.

Using the radiocarbon dating method on hundreds of items collected and tested, Prof. Piasetzky and Prof. Finkelstein presented a new and more accurate timeline in the history of ancient Israel, which was published in the New York Times, and had long-term implications for the study of the Biblical period since then.

 

The excavation site at Tel Megiddo, where it all began

Algorithms for reading ancient inscriptions

Prof. Piasetzky and Prof. Finkelstein continue their quest to reconstruct ancient history. As reported by The New York Times, they are conducting analyses to help better decipher ink inscriptions on potsherds, known as ostraca that were unearthed at an ancient fortress in the deep desert of Arad in southern Israel.

“The citadel of Arad stands like a time capsule: Active about 2,600 years ago, it was a relatively short-lived, godforsaken outpost, a five-day journey from Jerusalem, populated by maybe 30 soldiers,” describes Finkelstein. “Who inscribed the potsherds found there? Who read them? The ostraca teach us about government and about literacy in ancient Judah. If we determine when writing became a tool used by a wide swathe of society, we can shed light on when early Biblical texts were written.”

A shopping list from thousands of years ago

Prof. Piasetzky and Prof. Finkelstein have put together a team of archaeologists, historians, physicists, mathematicians, and computer scientists to analyze handwriting and determine just how many hands penned the Arad ostraca.

To do so, they employ physics techniques of multispectral imaging to reveal inscriptions and improve readability. Next, they compare handwriting by using algorithms specially developed by the team. What they found there was surprising: the new lines discovered were a letter requesting the issuance of wine and food from the warehouses of the Tel Arad fortress to one of the military units in the area. The recipient of the letter was the warehouse clerk, while the address was an officer from Beersheba.

Beyond the information about what people used to eat and drink during that time, the researchers revealed that even quartermasters knew how to read and write, and also learned a few new words that don’t appear in the Bible. “From the content of the letters we learn that literacy permeated even the low ranks of the military administration of the kingdom. If we extrapolate this data to other areas of Judea, and assume that this was the case in the civil administration and among the clergy, the level of literacy is considerable. This level of literacy is a reasonable background for the composition of Biblical texts,” explains Prof. Finkelstein.

Facing the future

After studying the past, Prof. Finkelstein and Prof. Piasetzky explain what can be done with these special technologies in the 2000s. “One may ask why a student of mathematics would be interested in developing tools for handwriting analysis of ancient inscriptions,” Prof. Piasetzky says. “But this type of analysis is also acutely needed today by, say, lawyers, banks, and the police. Furthermore, we’re finding solutions for the challenges of deciphering ink inscriptions found on uneven clay surfaces with faded markings and missing pieces. If our algorithms can analyze decayed inscriptions, think what they can do with modern-day handwriting on flat clean paper surfaces.”

Prof. Finkelstein adds: “With handwriting we face a problem of subjectivity. Scholars – all of us – come with preconceptions. We can convince ourselves that we see this or that particular letter. The computer does not have preconceptions. It measures length of strokes and angles, making numerical comparisons. Our next step is to integrate multispectral imaging at digs. This could dramatically improve excavation methodologies by determining on site if a potsherd is treasure or junk. One inscription can change the way we understand history.”

Featured image: Prof. Eli Piasetzky and Prof. Israel Finkelstein talk about how it all started

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Astronomy,Chemistry,Physics

Conversations in the Clean Room

At the shared laboratories of the Center for Nanoscience and Nanotechnology, casual conversations between scientists can lead to breakthroughs

A chemist and a physicist walk into a clean room. No, this is not the one about how many people it takes to change a light bulb. Nor is it the one about two Israelis and three opinions. This is a true story about how two doctoral students from different fields got talking and realized that they may be able to use chemistry to solve a nagging problem in physics. “These students were the best kind – curious and open to new ideas and different ways of approaching a problem,” says Prof. Gil Markovich of the Raymond and Beverly Sackler School of Chemistry. Prof. Yoram Dagan, Raymond and Beverly Sackler School of Physics and Astronomy, nods in agreement.

Markovich and Dagan were the students’ respective PhD advisors and quickly saw the benefit of collaborating. In their research, they sought a solution to prevent damage to the surface of semiconductors – small components that control electrical current in devices such as computers and mobile phones, which damage the functioning of the devices.

For this kind of research, a particularly sterile laboratory is required. The special conditions in the “clean room” include a constant temperature of 20 degrees, 50 percent humidity, and a very powerful filter that prevents the entry of dust particles into the laboratory space and is responsible for creating a sterile work environment. These conditions are essential for the production of certain materials, especially electronic chips, which can be disrupted by something as tiny as a grain of dust.

From cell phones to thermal cameras  

The scientists are using a chemical rather than physical process to create an electrical insulating thin film the thickness of a single atom. According to Dagan, “Unlike in physics, where non-organic materials are used, we used organic compounds to get the components that create the atom-thick layer.” In the process carried out by the scientists, they heated organic compounds to the point of dissolution. Once they touch the surface, they receive additional energy and break down until the process stops on its own. “This creates only a single layer of the insulating material, because there is not enough energy to form another layer,” Dagan explains. “In a cheap and rapid chemical process, we were able to offer an alternative to complicated and costly processes, and even to achieve a better result.”

Their invention could improve microelectronics in all the devices we carry in our pockets and have in our homes by making them faster, more efficient and more compact. “This is a long-term project – an idea that may be implementable twenty years down the line. Yet exploring this basic physics problem using nano-chemistry led us to an application that can be realized today,” says Dagan.

Markovich and Dagan have teamed up with industry experts for guidance in applying their technology to improve resolution in infrared cameras used for defense and security installations. The Israel Innovation Authority (formerly the Office of the Chief Scientist) has invested in the project with a grant reserved solely for projects that have a good chance to be commercialized in Israel. “It all begins, though, with basic science. Basic science is the foundation of knowledge. When we discover new possibilities and new materials, applications can grow,” stresses Dagan.

Collaboration opens new possibilities

Markovich and Dagan share a passion for unlocking the secrets of the universe: “We are both interested in origins,” says Dagan. “Gil researches the interaction of minerals with amino acids and DNA – the original building blocks of life.  I am interested in the fundamental properties of matter and materials. I would not think up chemical approaches to physical problems by myself. Our collaboration is opening up new possibilities.” says Dagan.

“This has been a fun ride,” adds Markovich. “First, Yoram is a nice person. And I never worked on these kinds of problems before. We have ideas for cooperation on chemical ways to create new materials for quantum computing. The future is wide open.” 

Featured iage:Prof. Gil Markovich and Prof. Yoram Dagan (Photo: Yoram Reshef)

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Honours & Awards,Physics

Congratulations to Itamar Cohen who was chosen for the first cohort of the Jabotinsky Fellowship in the field of applied science

Itamar is a doctoral student at the School of Physics and Astronomy, in the direct Ph.D. program

Mr. Itamar Cohen was chosen for the first cohort of the Jabotinsky Fellowship in the field of applied science, awarded by the ministry of science to students in the direct-PhD track.

In his research, Itamar investigates how intense laser pulses can accelerate electrons to high energies.

For decades, these high energy electrons could only be generated at large accelerator facilities. Itamar’s work, however, is conducted at a university-scale laboratory located at our basement at the School of Physics. His experiments are conducted using a high-intensity laser with peak power of 20,000,000,000,00 Watts (20 TeraWatts). The technology which enabled minimizing the size and cost of this intense laser is called “Chirped Pulse Amplification” and its inventors were awarded the Nobel Prize in Physics this year.

Itamar’s research aims to generate high-energy electrons in a cheep and compact manner, and to employ them in a range of areas such as medicine, manufacturing, security, and even fundamental studies of our universe.

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Physics

A new revelation about neutron stars

Multidisciplinary study finds that a small fraction of protons in neutron-dense objects can significantly impact their properties

Neutron stars are the smallest, densest stars in the universe, born out of the gravitational collapse of extremely massive stars. True to their name, neutron stars are composed almost entirely of neutrons — neutral subatomic particles that have been compressed into a small, incredibly dense celestial package.

A new study in Nature suggests that some properties of neutron stars may be influenced not only by their multitude of densely packed neutrons, but also by a substantially smaller fraction of protons — positively charged particles that make up just 5 percent of a neutron star. Because protons may carry substantially more energy than previously thought, they may contribute to properties of a neutron star such as its stiffness, its ratio of mass to size and its process of cooling.

The research was led by Prof. Eli Piasetzky of Tel Aviv University‘s School of Physics, Prof. Or Hen of the Massachusetts Institute of Technology (MIT), and Prof. Larry Weinstein of Old Dominion University. The graduate student who analyzed the data was Meytal Duer of TAU’s School of Physics.

Protons more significant than originally believed

“This finding may shake up scientists’ understanding of how neutron stars behave,” says Prof. Hen of MIT’s Laboratory of Nuclear Science.

“We think that when you have a neutron-rich nucleus, the protons move faster than the neutrons, so in some sense protons carry the action on average,” Prof. Hen continues. “Even though protons are the minority in the star, we think the minority rules. Protons seem to be very active, and we think they might determine several properties of the star.”

“The cosmological abundance of nuclei is not well understood,” says Prof. Piasetzky. “We think that the merging of two neutron stars is one of the main processes in the universe that create nuclei heavier than iron, such as gold. Our study of neutron-rich nuclei indicates that we must reconsider the role played by the small fraction of protons in the neutron star and its impact on the nuclei creation process.”

The researchers looked for signs of proton and neutron pairs in carbon, aluminium, iron and lead nuclei, each with a progressively higher ratio of neutrons to protons. They found that, as the relative number of neutrons in an atom increased, so did the probability that a proton would form an energetic pair. The likelihood that a neutron would pair up, however, stayed about the same.

“This trend suggests that, in objects with high neutron density, the minority protons carry a disproportionally large part of the average energy,” says Prof. Piasetzky.

Squeezing more science out of an experiment

Research for the study was based on data previously collected by CLAS — the CEBAF (Continuous Electron Beam Accelerator Facility) Large Acceptance Spectrometer, a particle accelerator and detector based at Thomas Jefferson Laboratory in Virginia. The team chose to mine data collected during a 2004 experiment in which electrons bombarded carbon, iron and lead nuclei, with the goal of observing how particles produced in nuclear interactions travel through each nucleus’s respectively larger volume.

Along with their varying sizes, each of the four nuclei has a different ratio of neutrons to protons, with carbon having the fewest neutrons and lead the most. The group studied the data for signs of high-energy protons and neutrons — indications that the particles had paired up — and whether the probability of this pairing changed as the ratio of neutrons to protons increased.

“People were using the detector to look at specific interactions, but it also measured a bunch of other reactions that took place at the same time,” says Prof. Larry Weinstein of Old Dominion University. “So we thought, let’s dig into this data and see if there’s anything interesting there. We want to squeeze as much science as we can out of experiments that have already run.”

Eventually, the team observed that as the number of neutrons in an atom’s nucleus increased, the probability of protons having high energies (and having paired up with a neutron) increased significantly. The probability for neutrons to have these high energies remained the same.

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