Glucose-Responsive Monoolein Cubic Phase Containing Glucose Oxidase

Glucose-responsive monoolein (MO) cubic phase was prepared by immobilizing proteinoid composed of Asp and Leu (PAL) and hydrophobically modified glucose oxidase (HmGOD) onto the MO bilayers. The hydrodynamic mean diameter of PAL aggregate in aqueous solution decreased with increasing the pH value. The number of pamitic acid residue per one molecule of HmGOD was determined to be 6.3 by a calorimetric method. HmGOD could acidify glucose solution in a few hours, possibly because it converted glucose to gluconic acid. PAL- and HmGOD-immobilized MO cubic phase was prepared by hydrating MO melt with the mixture aqueous solution of PAL and HmGOD. The cubic phase exhibited its phase transition around 62.5°C, determined by polarizing microscopy. The release of carboxylic fluorescein (CF) from the cubic phase was suppressed when the pH value of release medium decreased, possibly because PAL can aggregate more at a lower pH value. The release was suppressed when glucose concentration increased, possibly because the release medium can be more acidified and PAL will be more aggregated at a higher glucose concentration. The cubic phase could be used as a drug carrier which releases its content in a sustained manner when the glucose concentration is abnormally high.     

Preparation and characterization of self-assembled nanoparticles based on glycol chitosan bearing adriamycin

An anthracycline drug, adriamycin, was chemically conjugated onto the backbone of glycol chitosan via an acid-labile cis-aconityl linkage. The physicochemical characteristics of the glycol chitosan–adriamycin (GC–ADR) conjugates were investigated by dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. The GC–ADR conjugates were capable of forming nano-sized self-aggregates in an aqueous medium, when the adriamycin content in the conjugate was in the range of 2.0–5.0 wt.%. The self-aggregates were spherical in shape, and had mean diameters of 238–304 nm, depending on the adriamycin content. The critical aggregation concentrations of the conjugates, estimated by the fluorescence quenching method, were as low as 1.0–2.5×10⁻² mg/ml. The size of self-aggregates was not affected by the polymer concentration in the range from 50 to 2,000 μg/ml, and was maintained up to 8 days in phosphate-buffered saline (pH 7.4), indicating high colloidal stability. The release of adriamycin from self-aggregates was significantly dependent on the pH of the medium due to the cis-aconityl linkage; e.g., the amount of adriamycin released for 4 days was 7.3±0.3% at pH 7, whereas it was 29.3±1.9% at pH 4. The cell viability results demonstrated that free adriamycin shows more potent cytotoxicity than the conjugates, primarily attributed to the sustained release of adriamycin from self-aggregates. In conclusion, the self-aggregates, formed by GC–ADR conjugates, might be useful for the site-specific delivery of adriamycin in a sustained manner.     

Optical orthogonal code-division multiple-access system .II.Multibits/sequence-period OOCDMA

For part I see ibid. vol.42, no.7, p.2470 (1994). In a recently proposed optical orthogonal code division multiple-access (OOCDMA) system, one bit of user's data is transmitted per sequence-period, and a threshold is employed for the final bit decision. In this paper, a system that can transmit multibits per sequence-period is introduced, and avalanche photodiode (APD) noise, thermal noise, and interference, are included. This system, derived by exploiting orthogonal properties of the OOCDMA code sequence and using a maximum search (instead of a threshold) in the final decision, is log₂ F times higher in throughput, where F is sequence-period. For example, four orders of magnitude are better in bit error probability at -56 dBW received laser power, with F=1000 chips, 10 “marks” in a sequence, and 10 users of 30 Mb/s data rate for one-bit/sequence-period and 270 Mb/s data rate for multibits/sequence-period system. Furthermore, an exact analysis is performed for the log₂F bits/sequence-period system with a hard-limiter placed before the receiver, and its performance is compared to the performance without hard-limiter, for the chip-synchronous case. The improvement from using a hard-limiter is significant in the log₂F bits/sequence-period OCCDMA system (while it is not in a one-bit/sequence-period OOCDMA system proposed in Part I)     

Nanoshuttered OLEDs: Unveiled Invisible Auxiliary Electrode

In this study, organic light‐emitting diodes (OLEDs) with enhanced optical properties are fabricated by inserting a nanosized stripe auxiliary electrode layer (nSAEL) between the substrate and an indium tin oxide (ITO) layer. This design can avoid the shortcomings of conventional microsized layers while maintaining high optical uniformity due to the improved conductivity of the electrode. The primary advantage is that the nSAEL (submicrometer scale) is no longer visible to the naked eye. Moreover, the reflective shuttered (grating) structure of the nSAEL increases the forward‐directed light by the microcavity (MC) effect and minimizes the loss of light by the extracting the surface plasmon polariton (SPP) mode. In this study, the degree of the MC and SPP can be controlled with the parameters of the nSAEL by simply conjugating the conditions of laser interference lithography (LIL). Therefore, the current and power efficiencies of the device with an nSAEL with optimized parameters are 1.17 and 1.23 times higher than the reference device at 1000 cd/m², respectively, and at these parameters, the overall sheet resistance is reduced to less than half (48%). All of the processes are verified by comparing the computational simulation results and the experimental results obtained with the actual fabricated device.     

A Distributed Cooperative MAC Protocol for QoS Improvement and Mobility Support in WiMedia Networks

A Distributed Medium Access Control (D-MAC) protocol based on UWB for high-rate Wireless Personal Area Networks is specified by the WiMedia Alliance. D-MAC protocol is suitable for ubiquitous connection in home networks, military/medical applications due to its inexpensive cost, low power consumption, high data rate, and distributed approach. In contrast to IEEE 802.15.3, D-MAC makes all devices have the same functionality. And its networks are self-organized and provide devices with functions such as access to the medium, channel allocation to devices, data transmission, quality of service and synchronization in a distributed manner. D-MAC fundamentally removes the problems of the centralized MAC approach revealed at IEEE 802.15.3 MAC by adopting a distributed architecture. However, the current D-MAC can’t prevent QoS degradations, occurred by mobile nodes with low data rate due to bad channel status, which cause critical problems in QoS provisioning to isochronous streams and mobile applications. Therefore, we propose a distributed cooperative MAC protocol for multi-hop WiMedia networks using virtual MIMO links. Based on instantaneous Channel State Information among WiMedia devices, our proposed protocol can intelligently select the transmission path with higher data rate to provide advanced QoS with minimum delay for real-time multimedia streaming services.     

The effect of a market factor on information flow between stocks using the minimal spanning tree

We empirically investigated the effects of market factors on the information flow created from N(N−1)/2 linkage relationships among stocks. We also examined the possibility of employing the minimal spanning tree (MST) method, which is capable of reducing the number of links to N−1. We determined that market factors carry important information value regarding information flow among stocks. Moreover, the information flow among stocks showed time-varying properties according to the changes in market status. In particular, we noted that the information flow increased dramatically during periods of market crises. Finally, we confirmed, via the MST method, that the information flow among stocks could be assessed effectively with the reduced linkage relationships among all links among stocks from the perspective of the overall market.     

Probability-Based Optimization of Inter-Sensing Duration and Power Control in Cognitive Radio

Probability-based strategies are proposed in this letter to determine the optimal inter-sensing duration and power control for cognitive radio (CR). With utilization of the statistics of licensed band occupancy, appropriate inter-sensing duration is determined to capture the recurrence of spectrum opportunity in time when the licensed signal is detected, or to achieve the maximum spectrum efficiency under a certain level of interference with licensed communication when the licensed signal is declared absent. Transmit power is varied dynamically according to the non-interfering probability at each sample so as to increase the transmission rate and decrease the interference power.     

A Comparative Study of HBr-Ar and HBr-Cl<Subscript>2</Subscript> Plasma Chemistries for Dry Etch Applications

The effects of HBr/Ar and HBr/Cl₂ mixing ratios in the ranges of 0–100% Ar or Cl₂ on plasma parameters, densities of active species influencing the dry etch mechanisms were analyzed at fixed total gas flow rate of 40 sccm, total gas pressure of 6 mTorr, input power of 700 W and bias power of 300 W. The investigation combined plasma diagnostics by Langmuir probes and the 0-dimensional plasma modeling. It was found that the dilution of HBr by Ar results in maximum effect on the ion energy flux with expected impact on the etch rate in the ion-flux-limited etch regime, while the addition of Cl₂ influences mainly the relative fluxes of Br and Cl atoms on the etched surface with expected impact on the etch rate in the reaction-rate-limited etch regime.     

Photoinitiated RAFT polymerization of vinyl acetate

A photoinitiation process was investigated to develop a rapid and well‐controlled RAFT polymerization method applied to vinyl acetate (VAc) using methyl (ethoxycarbonothioyl)sulfanyl acetate (MESA) and bis(2,4,6‐trimethylbenzoyl)phenylphosphine oxide as the RAFT agent and photoinitiator, respectively. MESA was selected as the photochemically inert RAFT agent to minimize photolysis of the thiocarbonylthio groups during polymerization. Poly(vinyl acetate) with a prespecified well‐controlled molecular weight (MW) and a narrow MW distribution was successfully synthesized. The polymerization reaction proceeded as a living polymerization and was remarkably rapid compared with approaches that use thermally initiated processes with a very short induction period. A detailed kinetic study of the mechanism underlying the polymerization reaction, however, revealed that the chain ends containing xanthate moieties were not perfectly stable upon UV‐irradiation, and they generated radicals via homolytic cleavage. This reaction appeared to proceed by a combination of a degenerative transfer RAFT mechanism and a dissociation‐combination mechanism. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Highly linear and low noise differential bipolar MOSFET down-converter in CMOS process

A highly linear, low noise differential down-converter employing a new linearisation technique derived from composite transistors, i.e. nMOSFET and vertical NPN BJT, is proposed and implemented in a 0.18 μm CMOS technology. It draws 1 mA from a 2.5 V supply voltage and has a voltage gain of 13 dB, a double-sideband noise figure of 9.5 dB, an IIP2 of more than 49 dBm, and an IIP3 of 6.5 dBm.