7,691 research outputs found
Clustering and dynamics of cytochrome bd-I complexes in the Escherichia coli plasma membrane in vivo.
No full textThe cytochrome bd-I complex of Escherichia coli is a respiratory terminal oxidase and an integral component of the cytoplasmic membrane. As with other respiratory components, the organization and dynamics of this complex in living membranes is unknown. We set out to visualize the distribution and dynamics of this complex in vivo. By exchanging cydB for cydB-gfpgcn4 on the E. coli chromosome, we produced a strain (YTL01) that expresses functional GFP-tagged cytochrome bd-I terminal oxidase complexes under wild-type genetic control. We imaged live YTL01 cells using video-rate epifluorescence and total internal reflection fluorescence (TIRF) microscopy in combination with fluorescence recovery after photobleaching (FRAP) and saw mobile spots of GFP fluorescence in plasma membranes. Numbers of GFP molecules per spot were quantified by step-wise photobleaching giving a broad distribution with a mean of approximately 76, indicating that cytochrome bd-I is concentrated in mobile patches in the E. coli plasma membrane. We hypothesize that respiration occurs in mobile membrane patches which we call 'respirazones'
Magnetic uniaxial alignment of the columnar superstructure of discotic metallomesogens over the centimetre length scale
No full textThe uniaxial alignments of the columnar superstructure of discotic metallomesogens, cobalt octa( n-dodecylthio) porphyrazine (CoS12), over the centimetre length scale have been achieved by spinning samples under a static magnetic field. The orientations of the columnar superstructures were investigated by small angle neutron scattering ( SANS) and cryogenic transmission electron microscopy (cryo-TEM). Upon cooling from the isotropic phase to the columnar mesophase in the presence of a static magnetic field (0.4 - 1.1 T), CoS12 formed oriented columnar superstructures with the columnar directors being isotropically distributed in the plane normal to the external magnetic field. When the samples were continuously spun during cooling in a static applied magnetic field of 1.0 T, CoS12 was observed to form uniaxially aligned columnar superstructures with the columnar domain directors being parallel to the rotation axis which was normal to the external field. The optimal rotation speed for the alignment was found to be as low as 5 - 10 rpm, where the full width at half maximum of the domain director distribution is minimized. The uniaxial alignments were achieved over a macroscopic length scale (ca. 1 cm). Cryo-TEM measurements revealed that the persistence length of the uniaxially aligned columns was at least 1 mu m.This work was supported by the program of the Basic Atomic
Energy Research Institute (BAERI) which is a part of the
Nuclear R&D Programs funded by the Ministry of Science &
Technology (MOST) of Korea and the HANARO Utilization
Program (M2-0363-00-0063). We thank the HANARO at
KAERI and NCNR at NIST for SANS beamtime supports.
The work utilized NIST facilities supported in part by the
National Science Foundation under DMR-9986442. We also
thank J.-K. Kim, S.-M. Kim and J.-Y. Lee at Korea Basic
Science Institute (KBSI) for technical assistance during
cryo-TEM measurements and J.-S. Lee for DSC and POM
measurements
Low-power charge-sharing ROM using dummy bit lines
No full textA shared-capacitor charge-sharing ROM (SCCS-ROM) is proposed to lower the bit line swing voltage by using charge-sharing. It uses only three capacitors for the charge-sharing and it implements the capacitors with dummy bit lines. This not only increases noise immunity but also reduces power. The SCCS-ROM achieves 8.4% power reduction.This work was supported by KOSEF through the MICROS at KAIST, Korea
A low-power charge-recycling ROM architecture
No full textThis paper describes a newly proposed low-power charge-recycling read-only memory (CR-ROM) architecture. The CR-ROM reduces the power consumption in bit lines, word lines, and precharge lines by recycling the previously used charge. In the proposed CR-ROM, bit-line swing voltage is lowered by the charge recycling between bit lines. When N bit lines recycle their charges, the swing voltage and the power of the bit lines become 1/N and 1/N-2 compared to the conventional ROMs, respectively. As the number of N increases, the power saving in bit lines becomes salient. Also, power consumption in word lines and precharge lines can be reduced theoretically to half by the proposed charge-recycling techniques. The simulation results show that the CR-ROM consumes 60%similar to85% of the conventional low-power ROMs with 1 K x 32 b. A CR-ROM with 32 kb was implemented in a 0.35-mum CMOS process. The power dissipation is 6.60 mW at 100 MHz with 3.3 V and the maximum operating clock frequency is 150 MHz
A low-power ROM using charge recycling and charge sharing techniques
No full textIn a memory, most power is dissipated in high-capacitive lines such as predecoder lines, wordlines, and bitlines. To reduce the power dissipation in these high-capacitive lines, this paper proposes three techniques using charge recycling and charge sharing. The first is the charge recycling predecoder (CRPD) , the second is the charge recycling wordline decoder (CRWD), and the last one is the charge sharing bitline (CSBL) for a ROM. The CRPD and the CRVM recycle the previously used charge in predecoder lines and wordlines. Theoretically, the power consumption in predecoder lines and wordlines are reduced to a half. The CSBL reduces the swing voltage in the ROM bitlines to very small voltage using a charge sharing technique with three small capacitors. The CSBL can significantly reduce the power dissipation in ROM bitlines. The CRPD, the CRWD, and the CSBL consume 82%, 72%, and 64%, respectively, of the power of previous ROM designs. A charge recycling and charge sharing ROM (CRCS-ROM) with the CRPD, the CRWD, and the CSBL is implemented. A CRCS-ROM with 8K x 16 bits was fabricated in a 0.35-mum CMOS process. The CRCS-ROM consumes 8.63 mW at 100 MHz with 3.3 V. The chip core area is 0.51 mm(2)
Effects of conductivity and dielectric behaviors on the electrorheological response of a semiconductive poly(p-phenylene) suspension
No full textWe considered the electrorheological (ER) properties of an anhydrous suspension based on a semiconducting polymer. In order to investigate the effects of the electrical properties of polymeric particles on the ER phenomena, poly(p-phenylene) was synthesized and endowed with semiconductivity by doping with FeCl3 solutions. The dielectric behaviors of ER suspension revealed facilitated interfacial polarization for the appropriately doped suspension with intermediate conductivity of particle. These behaviors were found to be closely related with the magnitude of dynamic yield stress, which showed a maximum and then decreased with increasing conductivity of particles. Therefore, we established an optimum condition of FeCl3 doping of poly (p-phenylene) showing the maximum ER activity. Dynamic viscoelastic properties of the ER suspension were also characterized for the limited case. These experimental results give a clear relationship between the conductivity of semiconductive particles and their ER behaviors. Furthermore, effects of the interfacial polarization on yield stress behaviors were investigated using surfactant-activated ER suspensions. Over a wide range of temperature, our suspensions show good ER activity while retaining the low current density that would broaden the potential applicability of the ER fluids. (C) 1998 Academic Press
Electrorheological Behaviors of Polyaniline Suspensions based on the Complex Dispersing Medium
No full textA HIGH SPEED DIRECT DIGITAL FREQUENCY SYNTHESIZER USING A LOW POWER PIPELINED PARALLEL ACCUMULATOR
No full textISCAS.2002This work was supported by KOSEF through the MICROS at KAIST, Korea
Dielectric and rheological, behaviors of semiconductive polymer suspension as an electrorheological fluid
No full textWe have studied the dielectric and rheological characteristics of semiconductive polymer based ER fluids. Under static electric field, yield stress of suspension was found to be closely related to the dielectric properties: that is in accord with the Maxwell-Wagner interfacial polarization. The dielectric constant showed maximum then decreased with increasing bulk conductivity of particle as the yield stress behaviors did. Particle-medium interaction on ER response was also examined by utilizing appropriate surfactant. These experimental results were consistent with the prediction based on the recent model studies. Over wide range of temperature, our ER fluid maintains its activity so that it can broaden the potential applicability as a smart material
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