Watching Microcurrents Flow
    We can now watch electricity as it flows through even the tiniest circuits. By scanning the magnetic field generated as electric currents flow through objects, physicists have managed _____(1)_____ The technology will allow manufacturers to scan microchips for faults, as well as revealing microscopic defects in anything from aircraft to banknotes.
    Gang Xiao and Ben Schrage at Brown University in Providence, Rhode Island, visualize the current by measuring subtle changes in the magnetic field of an object and _____(2)_____.
    Their sensor is adapted from an existing piece of technology that is used to measure large magnetic fields in computer hard drives. “We redesigned the magnetic sensor to make it capable of measuring very weak changes in magnetic fields,” says Xiao.
    The resulting device is capable of detecting a current as weak as 10 microamperes, even when the wire is buried deep within a chip, and it shows up features as small as 40 nanometers across.
    At present, engineers looking for defects in a chip have to peel off the layers and examine the circuits visually; this is one of the obstacles _____(3) ______. But the new magnetic microscope is sensitive enough to look inside chips and reveal faults such as short circuits, nicks in the wires or electro migration—where a dense area of current picks up surrounding atoms and moves them along. “It is like watching a river flow,” explains Xiao.
    As well as scanning tiny circuits, the microscope can be used to reveal the internal structure of any object capable of conducting electricity. For example, it could look directly at microscopic cracks in an aeroplane’s fuselage, _____(4)_____. The technique cannot yet pick up electrical activity in the human brain because the current there is too small, but Xiao doesn’t rule it out in the future. “I can never say never,” he says.
    Although the researchers have only just made the technical details of the microscope public, it is already on sale, from electronics company Micro Magnetics in Fall River, Massachusetts. It is currently the size of a refrigerator and takes several minutes to scan a circuit, but Xiao and Schrage are working _____(5)_____.

A  to shrink it to the size of a desktop computer and cut the scanning time to 30 seconds
B  to making chips any smaller
C  to take tiny chips we require
D  to picture the progress of the currents
E  converting the information into a color picture showing the density of current at each point
F  faults in the metal strip of a forged banknote or bacteria in a water sample
Reinventing the Table
    An earth scientist has rejigged the periodic table to make chemistry simpler to teach to students.
    _____(1)_____ But Bruce Railsback from the University of Georgia says he is the first to create a table that breaks with tradition and shows the ions of each element rather than just the elements themselves.
    “I got tired of breaking my arms trying to explain the periodic table to earth students,” he says, criss-crossing his hands in the air and pointing to different bits of a traditional table. _____(2)_____ But he has added contour lines to charge density, helping to explain which ions react with which.
    “Geochemists just want an intuitive sense of what’s going on with the elements,” says Albert Galy from the University of Cambridge _____(3)_____
    _____(4)_____ He explains that sulphur, for example, shows up in three different spots one—for sulphide, which is found in minerals, one for sulphite, and one for sulphate, which is found in sea slat, for instance.
    He has also included symbols to show which ions are nutrients, and which are common in soil or water. _____(5)_____

A  There have been many attempts to redesign the periodic table since Dmitri Mendeleev drew it up in 1871.
B  Railsback has still ordered the elements according to the number of protons they have.
C  “I imagine this would be good for undergraduates.”
D  Raisback has listed some elements more than once.
E  And the size of element’s symbol reflects how much of it is found in the Earth’s crust.
F  The traditional periodic table was well drawn.