Ammonia assimilation in Klebsiella pneumoniae F-5-2 that can utilize ammonium and nitrate ions simultaneously: purification and characterization of glutamate dehydrogenase and glutamine synthetase

The two ammonia-assimilating enzymes glutamate dehydrogenase (GDH; EC 1.4.1.4) and glutamine synthetase (GS; EC 6.3.1.2) were synthesized steadily during the cell growth of Klebsiella pneumoniae F-5-2 that can utilize NH4+ and NO3- simultaneously under aerobic conditions. The enzymes were purified to homogeneity from cell extracts and characterized. The molecular mass of the purified GDH was 300 kDa with six identical 52-kDa subunits. GDH showed its maximal activity (aminating) at pH 8.0 and was stable between pHs 5.5 and 11.5. The enzyme was NADP-specific and strongly inhibited by Ag+. It catalyzed the amination of 2-ketovalerate, 2-ketoadipate, and 2-ketobutyrate, in addition to 2-ketoglutarate. The purified GS has a molecular mass of 470 kDa with eight identical 60-kDa subunits. GS showed its maximal activity at pH 8.0 and was stable between pHs 6.0 and 7.0. The enzyme was strongly inhibited by Fe3+, Hg2+, and Cu2+.     

Synchronized fresh cell bioreactor system for continuous L-(+)-lactic acid production using Lactococcus lactis IO-1 in hydrolysed sago starch

An efficient bioreactor, termed a 'synchronized fresh cell bioreactor', was developed and consisted of a pH-dependent substrate feed system coupled with cross flow filtration and turbidity control. The effect of high dilution rate and high cell density coupled with high cell viability on the production of l-lactic acid in continuous culture by Lactococcus lactis IO-1 in enzyme-hydrolysed sago starch medium was investigated. For all changes in dilution rate, cells responded in a synchronized way to the addition of glucose by increasing the rate of biomass formation. Consequently, a glucose-free feed solution was required to maintain the cell concentration at a particular pre-set value. This set-up facilitated the maintenance of the cells in a permanent log phase. At a cell concentration of 15 gl(-1) and a feed glucose concentration of 53 gl(-1), volumetric LA productivities of 8.2, 19.3 and 33.1 gl(-1)h(-1) were obtained at dilution rates of 0.21, 0.50 and 1.1 h(-1), respectively. The respective residual glucose concentrations in the spent medium were 1.90, 0.24 and 3.80 gl(-1). By increasing the cell density, the volumetric productivity increased proportionally. At high cell density, higher dilution rates resulted in lower lactate concentrations in the culture medium resulting in higher productivity. This reactor facilitated efficient operation with high cell viability by maintaining the cells in continuous growth phase for long-term fermentation. Therefore, the growth rate (mu) was calculated according to the Monod equation. Using this system, high specific productivities can be obtained which guarantees high commercial productivity at economical cost with only a small investment for setting up the sago industry.     

Reliability of signals from a chronically implanted, silicon-based electrode array in non-human primate primary motor cortex.

Multiple-electrode arrays are valuable both as a research tool and as a sensor for neuromotor prosthetic devices, which could potentially restore voluntary motion and functional independence to paralyzed humans. Long-term array reliability is an important requirement for these applications. Here, we demonstrate the reliability of a regular array of 100 microelectrodes to obtain neural recordings from primary motor cortex (MI) of monkeys for at least three months and up to 1.5 years. We implanted Bionic (Cyberkinetics, Inc., Foxboro, MA) silicon probe arrays in MI of three Macaque monkeys. Neural signals were recorded during performance of an eight-direction, push-button task. Recording reliability was evaluated for 18, 35, or 51 sessions distributed over 83, 179, and 569 days after implantation, respectively, using qualitative and quantitative measures. A four-point signal quality scale was defined based on the waveform amplitude relative to noise. A single observer applied this scale to score signal quality for each electrode. A mean of 120 (+/- 17.6 SD), 146 (+/- 7.3), and 119 (+/- 16.9) neural-like waveforms were observed from 65-85 electrodes across subjects for all recording sessions of which over 80% were of high quality. Quantitative measures demonstrated that waveforms had signal-to-noise ratio (SNR) up to 20 with maximum peak-to-peak amplitude of over 1200 microv with a mean SNR of 4.8 for signals ranked as high quality. Mean signal quality did not change over the duration of the evaluation period (slope 0.001, 0.0068 and 0.03; NS). By contrast, neural waveform shape varied between, but not within days in all animals, suggesting a shifting population of recorded neurons over time. Arm-movement related modulation was common and 66% of all recorded neurons were tuned to reach direction. The ability for the array to record neural signals from parietal cortex was also established. These results demonstrate that neural recordings that can provide movement related signals for neural prostheses, as well as for fundamental research applications, can be reliably obtained for long time periods using a monolithic microelectrode array in primate MI and potentially from other cortical areas as well.     

Flow resistance of a liquid droplet confined between two hydrophobic surfaces

Flow resistance of a liquid droplet confined between two hydrophobic surfaces has been investigated experimentally and factors contributing to the flow resistance have been studied. A water droplet has been sheared between two hydrophobic surfaces and shear resistance has been measured. The experimental results show that the shear resistance at low shear velocities is primarily caused by asymmetrical surface tension due to the contact angle hysteresis. A droplet on a rough hydrophobic surface remains almost symmetrical under shear and exhibits extremely low friction. The shear resistance at high shear velocities is affected by viscous force. Furthermore, sliding angles of water droplets on micropatterned hydrophobic surfaces have been measured to clarify the effects of surface topography on flow resistance. Surfaces with many prismatic structures raised out of the plane tend to exhibit low sliding angles.     

Sensory‐motor control mechanism for reaching movements of a redundant musculo‐skeletal arm

This paper studies the human arm's sensory‐motor control mechanism in reaching movements. First, we formulate both the kinematics and dynamics of a two‐link planar arm model with six redundant muscles. The nonlinear muscle dynamics is modeled based on several biological understandings. We then show the stability of the overall system and perform some numerical simulations. By considering the internal forces induced by the redundant muscles, we show that the damping factors in each joint can be regulated, and as the result, it can realize humanlike quasistraight line reaching movements. In addition, we also propose the gravity compensation method at the muscle input level and present the result of numerical simulation to verify the usefulness of this method. © 2005 Wiley Periodicals, Inc.     

Development of a novel emitting vinyl polymer and its application in organic electroluminescent devices

Abstract— A novel emitting vinyl polymer, poly[4‐(7‐{4‐[N,N‐bis(9,9‐dimethylfluoren‐2‐yl)amino]phenyl}‐2,1,3‐benzothiadiazol‐4‐yl)phenylethylene] (PVFABT), was designed and synthesized. The new vinyl polymer was found to form smooth amorphous films with a high glass‐transition temperature of 199°C. The polymer possesses bipolar character with both electron‐donating and accepting properties. It undergoes reversible anodic oxidation and cathodic reduction to give stable cation and anion radicals. It exhibits intense orange fluorescence in solution and as film. A multilayer organic electroluminescent device using PVFABT as an emitting material emitted orange light, exhibiting high performance.     

Address‐While‐Display technique combined with gas‐discharge AND logic for driving AC‐PDPs

A hybrid AWD/AND drive technique has been developed in which an Address‐While‐Display (AWD) scheme is combined with an AND logic characteristic that gas discharges demonstrate. The AWD technique enables AC‐PDPs to be driven at high luminance, while the AND logic reduces the number of scan drivers by an order of magnitude. A detailed analysis of the addressing operation has been made. The hybrid drive utilizes the AND logic in two ways: (1) a combination of two voltage pulses and (2) a combination of a voltage pulse and discharge‐priming particles. It was found that the addressing operation requires the establishment of a discharge between the scan and data electrodes, and also between the scan and display electrodes.     

Conference assistant system for supporting knowledge sharing in academic communities

This paper describes our ongoing attempts to build a communityware system by presenting a project of providing digital assistants to support participants in an academic conference. We provided participants at the conference with a personal assistant system with mobile and ubiquitous computing technologies and facilitated communication among the participants. We also made online services available via the Web to encourage the participants to continue their relationships even after the conference. In this paper, we show the system we provided for the project and report the results.     

The Geometry of M/D/1 Queues and Large Deviation

Since an M/D/1 queue is represented by a Markov chain, we can consider the set of all the M/D/1 queues as a subset of Markov chains. A geometric structure is induced from the geometric structure of the set of Markov chains, which forms an exponential family. In this paper, we show that in the large deviation of the tail probability of the queue length of an M/D/1, the rate function and a twisted Markov chain, etc., are represented in terms of the geometry. Moreover, in the importance sampling (IS) simulation for the M/D/1 queue, we elucidate the geometric relation between the underlying distribution and a simulation distribution, and evaluate the variance of an IS estimate by geometric quantities.     

Analog Circuit Design Methodology in a Low Power RISC Microprocessor

There are various kinds of analog CMOS circuits in microprocessors. IOs, clock distribution circuits including PLL, memories are the main analog circuits. The circuit techniques to achieve low power dissipation combined with high performance in newest prototype chip in the Super H RISC engines are described. A TLB delay can be decreased by using a CAM with a differential amplifier to generate the match signal. The accelerator circuit also helps to speed up the TLB circuit, enabling single-cycle operation. A fabricated 96-mm² test chip with the super H architecture using 0.35-m four metal CMOS technology is capable of 167-MHz operation at 300 Dhrystone MIPS with 2.0-W power dissipation.