| RESEARCH HIGHLIGHTS |


just one copy of each chromosome. Mastl thus acts like a patrolman, keeping watch over this checkpoint so that it’s not skipped. To do this, it adds chemical tags that modulate the function of essential proteins involved in the process. In cell culture, Kaldis and his team


observed that the loss of Mastl could be overcome with drug treatment, suggesting that this might be a way to treat cancers triggered by mutated Mastl. However, “Mastl has multiple functions in mitosis,” notes Kaldis, “and we need to learn more about


these” before going ahead and blocking the protein in cancer patients.


1. Diril, M. K., Bisteau, X., Kitagawa, M., Caldez, M. J., Wee, S., Gunaratne, J., Lee, S. H. & Kaldis, P. Loss of the Greatwall kinase weakens the spindle assembly checkpoint. PLoS Genetics 12, e1006310 (2016).


Computer memory


REDUCING READ ERRORS MORE THAN A BIT


While we aspire to store increasing amounts of digital data on ever smaller devices, conven- tional memory technologies based on electron charge are reaching a physical limit on how much they can store in a given space. Alterna- tive storage methods are urgently needed. Kien Trinh, Sergio Ruocco and Massimo


Alioto at the A*STAR Data Storage Institute and National University of Singapore are inves- tigating a promising storage technique called spin-transfer torque magnetic random-access memory (STT-MRAM). In their pursuit, the


researchers have developed a voltage-boosting scheme for a STT-MRAM system, which greatly reduces errors incurred when reading data1. STT-MRAM works by exploiting elec-


trons’ intrinsic angular momentum, or spin, rather than their charge. Electron spin can take only two values — up or down — and a standard electrical current contains approxi- mately equal numbers of each. STT-MRAM uses a spin-polarized current, which has more of one spin type than the other, to exert a torque on magnetized ‘bitcells’. This flips


A NEW CIRCUIT SCHEME WOULD GREATLY INCREASE THE ACCURACY OF HIGH- DENSITY SPIN-BASED DATA STORAGE


the bitcell orientation to high or low states and thereby writes binary data. To read data, the surrounding circuitry must then detect small changes in the resistance of the bitcell, a difficult task to achieve without errors. “In the physical process of reading STT-


MRAM, there is an established trade-off between read disturbance (the chance of unintentionally flipping the bitcell when you read it) and read decision (reading the wrong value currently stored in the bitcell),” says Trinh. “To lower the read disturbance, the read current has to be small. However, a larger read current helps us distinguish between the high and low resistance states of the bitcell.” In other words, if you reduce one error, you increase the other. Trinh and co-workers trialed a new read


scheme in which the voltage in the system was boosted by switched capacitors. They performed extensive statistical simulations to find optimum electronic design settings that minimize the impact of natural variations. “We achieved a rate of just one error per


Spin-based memory, which exploits the intrinsic angular momentum of electrons, could offer faster, higher density computer memory than conven- tional technologies based on electron charge.


10 A*STAR RESEARCH


billion bitcell reads, compared to the conven- tional sensing scheme which has one per ten million,” says Alioto. “What’s more, our system is one of the first that can achieve so few errors while remaining suitable for low-power and low-voltage applications.”


ISSUE 6 | JANUARY – MARCH 2017


© Paul Hartmann Paludo/EyeEm/Getty


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56