While reading about an ancient Roman technique for maneuvering heavy stones using lead lumps, Prof. Shimon Reich of the Weizmann Institute's Materials and Interfaces Department came up with an idea: The age of ancient lead could be determined with the help of superconducting properties.

To put his idea to work, he enlisted the help of a metallurgist -  Dr. Grigorii Leitus of the Weizmann Institute -  and an archaeologist, Dr. Sariel Shalev of Haifa University and the Weizmann Institute's Helen and Martin Kimmel Center for Archaeological Science.

The widespread dating method currently used in archaeology -  called radiocarbon dating -  works only for objects containing carbon, such as bone and wood. Until now, no archaeological method existed to directly date the lead (or other metal) artifacts, often found in archaeological excavations.

Reich's method makes use of the fact that lead corrodes very slowly and that the products of corrosion accumulate on its surface (since they don't easily dissolve in water). Finding out how much corrosion has developed will give a good indication of how old the lead is. Yet how can one determine the amount of corrosion products in a lead object without affecting the object?

This is where superconductivity comes in. When frozen to a temperature below -266 degrees Celsius (around -447 degrees Fahrenheit), lead, in contrast to its corrosion products, becomes a superconductor (meaning an ideal conductor of electricity). Lead superconductors repel magnetic fields about 100,000 times more strongly than their corrosion products. By measuring the magnetic properties of the frozen lead artifact, one can accurately deduce the amount of uncorroded lead in the artifact. Then, weighing the object, one measures the mass of the lead metal along with its corrosion products. The difference between the two values yields the amount of corrosion.

Testing lead artifacts whose age was already known (via the context in which they were found), the scientists constructed a graph that correlates archaeological age and amount of corrosion (per unit area). This graph will be used in the future to date archaeological lead artifacts of unknown age. The technique is useful for artifacts found in ground that is not very acidic.

The lead artifacts examined were taken from excavation sites in Caesaria and Tel Dor, and derive from three different periods. The oldest was from the Persian period, around 2,500 years ago.

The next artifacts to be tested by this method will be taken from sunken ships. In antiquity, lead was used extensively to prevent barnacles from attaching themselves on the hulls of ships. The method could thus prove useful in fixing the age of marine ruins that are otherwise hard to date.

Prof. Reich is the incumbent of the Robert W. Reneker Chair of Industrial Chemistry.

In the first millionth of a second after the Big Bang, atoms as we know them today did not yet exist.

The jets of blazing matter that dispersed in all directions in those first few fractions of a second contained a mixture of infinitesimal particles (quarks and gluons), called the quark-gluon plasma. This was the first form of matter in the universe. Later on, when the universe cooled down a bit and became less dense, the quarks and gluons organized into various combinations, forming particles such as protons and neutrons. Since then, in fact, quarks and gluons have not existed as free particles in the universe.

Scientists have been trying to recreate the quark-gluon plasma in the lab in a joint experiment including 460 physicists from 57 research institutions in 12 countries. Recent results strongly indicate that they they are on the right track.

The ongoing project, called PHENIX, is being conducted at the Brookhaven National Laboratory in Long Island, using an accelerator, called RHIC (Relativistic Heavy Ion Collider), built especially for creating the quark-gluon plasma. The Israeli team is led by Prof. Itzhak Tserruya, head of the Weizmann Institute's Particle Physics Department. Tserruya and his colleagues designed and built special particle detectors, called pad chambers, which are a central part of PHENIX's detecting system.

The accelerator creates two beams of gold ions and accelerates them toward each other, causing a head-on collision. The power of the collision (about 40 trillion electron volts, the highest level of energy attainable in the lab) turns part of the beams' kinetic energy into heat, while the other part turns into various particles. The first stage in the creation of these new particles, like the first stage in the creation of matter in the Big Bang, is assumed to consist of the quark-gluon plasma.

Prof. Tserruya's research was supported by the Nella and Leon Benoziyo Center for High Energy Physics. He is the incumbent of the Samuel Sebba Professorial Chair of Pure and Applied Physics.

One of the ways to identify the quark-gluon plasma is by observing its interaction with other particles. When a single quark moves through regular matter, it emits radiation that slows down its progress somewhat. When it enters a very dense medium like quark-gluon plasma, its progress is slowed much more. That's precisely the phenomenon that has recently been observed and analyzed in the PHENIX project. According to physicists taking part in the experiment, these findings are very encouraging and could indicate that they have succeeded in creating the quark-gluon plasma.

Other than Tserruya, the Weizmann team participating in the PHENIX experiment included Prof. Zeev Fraenkel, Dr. Ilia Ravinovich, postdoctoral fellow Dr. Wei Xie and graduate students Alexandre Kozlov, Alexander Milov and Alexander Cherlin.

Skeptic: Billions of nerve cells in the human brain are involved in the process of vision. Since scientists find it difficult to understand even one of those cells, it's inconceivable that computers will ever be able to see.

Scientist: All the more reason to start working on it.

Prof. Brandt's research was supported by the Karl E. Gauss Minerva Center for Scientific Computation. He is the incumbent of the Elaine and Bram Goldsmith Professorial Chair of Applied Mathematics.

Prof. Basri conducts his research in the Moross Laboratory for Vision Research and Robotics.

While some people try to remember, others try unsuccessfully to forget. People whose memories have a debilitating effect, such as trauma sufferers who remain haunted by their experience throughout their lives, would benefit from the ability to intentionally dim or erase specific memories without affecting the others.

A step toward reaching this goal has recently been made by a Weizmann team. The scientists have uncovered a fundamental rule governing the workings of the brain. The findings were recently published in Science.

Every memory that we acquire undergoes a "ripening" process (called "consolidation"), which lasts a few hours after the memory is formed. During this time, certain treatments can erase that memory. Until recently, the accepted belief was that every memory consolidates just once, and after that the window of opportunity for erasing that memory closes.

However, recent evidence has shown that calling up a memory might again make it susceptible to disruption. If true, it might be possible to activate a "memory eraser" immediately after the act of remembering, even though years may have passed since the original memory was formed.

Yet leading labs in the world, spurred on by that evidence, came up with seemingly contradictory results: Working with animals, they found that only in some cases did it appear possible to erase old memories upon recall.

The current findings, made by Prof. Yadin Dudai of the Neurobiology Department, explain the puzzling discrepancies in the previous findings and shed light on how memories are recalled and stabilized.

Winner loses all

To understand the findings, think of the bits of information stored in our memories. Each may have many associations, some conflicting with others. For instance, a certain food can arouse memories of taste -  delicious or disagreeable; a person can be remembered in pleasant or unpleasant contexts, and so on. When we next taste the food or see the person, all of the associated memories are evoked. But in the end, only one of them will determine our reaction (i.e., become dominant). This memory dictates whether we will eat the food or reject it, whether we will smile at our acquaintance or ignore him. Dudai's team, which included Mark Eisenberg, Tali Kobilo and Diego Berman, found that only the memory that won the competition for dominance became sensitive to erasure. It is this memory that must be consolidated once again before being reinstalled in long-term memory. In other words, the winner, under the appropriate circumstances, loses all. In Dudai's words, "The stability of the recalled memory is inversely correlated with its dominance."

Dudai's team carried out the study with rats and fish. The rats learned to remember flavors; the fish learned to remember flashes of light. In both instances, the animals were trained to associate the stimuli with conflicting memories (the light, for instance, would signal danger only some of the time). In both species, researchers showed that the dominant memory was the only one that could be erased by administering an appropriate drug within a few minutes of recall.

Studies on humans have not yet been conducted, but Dudai points out that the closer we get to the basic principles of memory, the more similarities exist among animals, including humans. Thus drugs found to be effective in eliminating memories in animals may work in humans as well, offering a much awaited piece of good news to trauma sufferers.

DEFINING MEMORY

Dudai's recently published book, Memory from A to Z, provides a unique and valuable introduction to the field of memory for students and researchers alike. It consists of over 130 entries, bound within a coherent conceptual framework. Each entry starts with a definition, or set of definitions, followed by an in-depth and provocative discussion of the origin, meaning, usage and applicability of ideas and problems central to the science of memory and scientific culture at large. The entries provide a versatile tool kit as a source of definitions, information and further reading, as well as a trigger for contemplation, discussion and experimentation. The book can serve as a useful aid to study, teaching and debates, as well as a trigger for future experimentation.

Prof. Dudai's research was supported over the years by the Abe and Kathryn Selsky Foundation; the Nella and Leon Benoziyo Center for Neurosciences; the Lester Crown Brain Research Fund; the Abramson Family Brain Research Program; the Carl and Michaela Einhorn-Dominic Brain Research Institute; and the Murray H. & Meyer Grodetsky Center for Research of Higher Brain Functions. He is the incumbent of the Sara and Michael Sela Professorial Chair of Neurobiology.