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Matsunaga S.,Tohoku University | Natsui M.,Tohoku University | Ikeda S.,Tohoku University | Miura K.,Tohoku University | And 4 more authors.
Japanese Journal of Applied Physics

A perpendicular magnetic tunnel junction (P-MTJ)-based one-transistor/one- resistor (1T-1R) binary content-addressable memory (CAM) is proposed for a high-density nonvolatile CAM. The proposed CAM cell performs an equality-search operation between an input bit and the corresponding stored bit by detecting the difference of a "cell resistance", where the cell resistance is determined by the series connection of one metal-oxide-semiconductor (MOS) transistor and one P-MTJ device. This circuit structure makes it possible to implement a compact nonvolatile CAM cell circuit with 1.25 μm2 of a cell size in a 0.14μm complementary MOS (CMOS)/P-MTJ process. Moreover, the equality-search operation in a bit-serial fashion is used for great reduction of the activity rate in the proposed CAM cell array, since most of the mismatched words in the CAM are detected by just several higher bits of comparison results in the word circuits. By applying a bit-level fine-grained power gating scheme, a fabricated 64-bit × 128-word nonvolatile CAM achieves high density with maintaining low search energy under 3.1% of activity rate in the cell array. © 2011 The Japan Society of Applied Physics. Source

Hada N.,Meikai University | Okayasu M.,Meikai University | Ito J.,Meikai University | Nakayachi M.,Meikai University | And 8 more authors.

Although extensive studies have done much to clarify the molecular mechanisms of osteoclastogenesis during the last ten years, there may still be unknown molecules associated with osteoclast differentiation. Thus, we used fluorescent differential display to screen for genes whose expression is induced by receptor activator of NF-κB ligand (RANKL), a crucial molecule for osteoclast formation. We identified caveolin-1 (Cav-1) as a RANKL-induced gene. Cav-1 is a major structural protein of caveolae and lipid rafts, cholesterol-enriched microdomains in the plasma membrane (PM). The RANKL-induced Cav-1 was immediately conveyed to lipid rafts. Conversely, expression of flotillin-1 (Flot-1), another scaffolding protein of lipid rafts, was reduced during osteoclastogenesis, indicating conversion of Flot-1-predominant rafts into Cav-1-enriched rafts. However, in vitro osteoclastogenesis of precursor cells from Cav-1-null mice was comparable to that of wild-type mice, while Cav-2 expression in the knockout osteoclasts was maintained. Conversely, Cav-2 gene silencing in Cav-1-null osteoclast precursors using siRNA for Cav-2 increased osteoclast formation, suggesting that the Cav-1/Cav-2 complex may act as a negative regulator for osteoclastogenesis. On the other hand, destruction of lipid rafts by removal of cholesterol from the PM by methyl-ß-cyclodextrin (MCD) treatment caused disordered signal transductions for osteoclastogenesis, such as hyperactivation of Erk1/2 and insensitivity of Akt to RANKL stimulus. The abnormal signaling was reproduced by deleting exogenous lipoproteins from the culture medium, which also resulted in reduced osteoclast formation. In addition, the deletion caused delayed expression of nuclear factor of activated T cells c1 (NFATc1), and depressed its activation in the cytosol and inhibited its translocation into nuclei. Simultaneously, the deletion reduced the level of FcRγ, a trigger protein for initiating the calcium signaling needed to activate NFATc1, and decreased Cav-1 in lipid rafts. These findings indicate that the molecular mechanisms of osteoclastogenesis are highly dependent on extracellular lipoprotein and the integrity of lipid rafts, and suggest possible involvement of cholesterol. © 2011 Elsevier Inc. Source

Iga F.,Tohoku University | Kamiyanagi M.,Tohoku University | Ikeda S.,Tohoku University | Miur K.,Hitachi Advanced Research Laboratory | And 5 more authors.
IEICE Transactions on Electronics

In this paper, we have succeeded in the fabrication of high performance Magnetic Tunnel Junction (MTJ) which is integrated in CMOS circuit with 4-Metal/1-poly Gate 0.14 μm CMOS process. We have measured the DC characteristics of the MTJ that is fabricated on via metal of 3rd layer metal line. This MTJ of 60 × 180 nm2 achieves a large change in resistance of 3.52 kΩ (anti-parallel) with TMR ratio of 151% at room temperature, which is large enough for sensing scheme of standard CMOS logic. Furthermore, the write current is 320 μA that can be driven by a standard MOS transistor. As the results, it is shown that the DC performance of our fabricated MTJ integrated in CMOS circuits is very good for our novel spin logic (MTJ-based logic) device. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers. Source

Kamiyanagi M.,Tohoku University | Iga F.,Tohoku University | Ikeda S.,Tohoku University | Miura K.,Hitachi Advanced Research Laboratory | And 5 more authors.
IEICE Transactions on Electronics

In this paper, it is shown that our fabricated MTJ of 60 × 180 nm2, which is connected to the MOSFET in series by 3 levels via and 3 levels metal line, can dynamically operate with the programming current driven by 0.14 μm CMOSFET. In our measurement of transient characteristic of fabricated MTJ, the pulse current, which is generated by the MOSFET with an applied pulse voltage of 1.5V to its gate, injected to the fabricated MTJ connected to the MOSFET in series. By using the current measurement technique flowing in MTJ with sampling period of 10 nsec, for the first time, we succeeded in monitor that the transition speed of the resistance change of 60 × 180 nm2 MTJ is less than 30ns with its programming current of 500 μA and the resistance change of 1.2 kω. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers. Source

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