A simulation study of high‐order CMOS hyperbolic‐sine filters

This paper advances the field of externally linear–internally nonlinear (ELIN) filters by introducing a synthesis method that enables the design of high‐order class‐AB sinh filters by means of complementary metal–oxide semiconductor (CMOS) weak‐inversion sinh integrators comprising only one type of devices in their translinear loops. The proposed transistor‐level synthesis approach is demonstrated through the examples of (1) a biquadratic and (2) a fifth‐order filter, and their simulated performance is studied. The biquadratic filter achieves a dynamic range of 94 dB and has a tunable quality factor Q up to the value of 8, whereas its natural frequency can be tuned for four orders of magnitude. Its static power consumption amounts to 6.2 μW for Q = 1 and f_o = 2 kHz. The fifth‐order Chebyshev sinh CMOS filter with a cut‐off frequency of 100 Hz, a pass band ripple of 1 dB, and a power consumption of ~300 nW is compared head‐to‐head with its pseudo‐differential class‐AB CMOS log domain counterpart. The sinh filter achieves similar or better signal‐to‐noise ratio (SNR) and signal‐to‐noise‐plus‐distortion ratio (SNDR) performances with half the capacitor area but at the expense of higher power consumption from the same power supply level. All three presented filter topologies are novel. Cadence design framework simulations have been performed using the commercially available 0.35 µm AMS (austriamicrosystems) process parameters. Copyright © 2013 John Wiley & Sons, Ltd.     

Preliminary results from an analog implementation of first‐order TDCNN dynamics

This work falls into the category of linear cellular neural network (CNN) implementations. We detail the first investigative attempt on the CMOS analog VLSI implementation of a recently proposed network formalism, which introduces time‐derivative ‘diffusion’ between CNN cells for nonseparable spatiotemporal filtering applications—the temporal‐derivative CNNs (TDCNNs). The reported circuit consists of an array of Gm‐C filters arranged in a regular pattern across space. We show that the state–space coupling between the Gm‐C‐based array elements realizes stable and linear first‐order (temporal) TDCNN dynamics. The implementation is based on linearized operational transconductance amplifiers and Class‐AB current mirrors. Measured results from the investigative prototype chip that confirms the stability and linearity of the realized TDCNN are provided. The prototype chip has been built in the AMS 0.35 µm CMOS technology and occupies a total area of 12.6 mm sq, while consuming 1.2 µW per processing cell. Copyright © 2010 John Wiley & Sons, Ltd.     

CMOS weak‐inversion log‐domain glycolytic oscillator: a cytomimetic circuit example

This paper presents a 3 V, 1.21μW subthreshold log‐domain circuit which mimics the oscillations observed during the biochemical process of glycolysis due to the phosphofructokinase enzyme. The proposed electronic circuit is able to simulate the dynamics of the glycolytic oscillator and represent the time‐dependent concentration changes of the reactants and the products of the chemical process based on nonlinear differential equations which describe the biological system. By modifying specific circuit parameters, which correspond to certain chemical parameters, good agreement between the biochemical and electrical model results has been reached. The paper details the similarities between the equations that describe the biochemical process and the equations derived from the circuit analysis of a transistor and a source‐connected linear capacitor, a topology also known as the Bernoulli Cell. With the use of the Bernoulli Cell formalism, the chemical equations which describe the biochemical system have been transformed into their electrical equivalents. The analog circuit, which implements the whole process, has been synthesised, and simulation results including Monte Carlo analysis are provided, in order to verify the robustness of the proposed circuit and to compare its dynamics with prototype biological behaviour. Copyright © 2012 John Wiley & Sons, Ltd.     

A (Triphenylphosphine)Silver (I) Complex as a New Performance Additive in Free‐Radical Photopolymerization under Air

Unusual photochemical properties of an Ag(I)‐derived complex, i.e., bis[(µ‐chloro)bis(triphenylphosphine)silver (I)] ([Ag](PPh₃)) are demonstrated when used in free‐radical photopolymerization reactions: i) [Ag](PPh₃) can act as an innovative photoinitiating system when associated with a commercial type I photoinitiator 2,2‐dimethoxy‐2‐phenylacetophenone to overcome the oxygen inhibition effect during the free‐radical photopolymerization of acrylate monomers, thus accelerating the kinetics of polymerization under air; ii) silver‐based nanoparticles can be in situ generated under air, thus leading to new antibacterial coatings which prevent the growth of Escherichia coli and Staphylococcus aureus after few hours of incubation.     

The influence of processing methods on the dielectric properties of BaTi1-xGdxO3-x/2 - Based materials

In this study, the intermediate rare-earth oxide Gd₂O₃ (Gd) was substituted in different amounts (x = 0.2–2 mol%) for the formulation of BaTi_1-xGd_xO_3-x/2 (BTG_x) dielectric materials. The effect of B-site substitution was confirmed by the additional Raman active A_1g octahedral peak at ~835cm^-1 strengthened at x ≥ 0.4 mol%. Additionally, properties of 0.9BTG_0.007-0.1BA dielectric ceramics were analysed based on the influence of various processing methods as a function of sintering temperature. The focal samples were labelled Method-A (direct-mix) and Method-B (indirect-mix). As the sintering temperature (1075–1200 °C) increased, the 1 kHz response of the ε–T curves of Method-A samples transformed from a single peak to broad-narrow double peaks of high dielectric loss tangent (tan δ). Nonetheless, samples of Method-B possessed a clearly defined transmission electron microscopy (TEM) core-shell structure, flattened double-peak ε-T curves, optimised dielectric properties (ε = ~1563–1851 and tan δ < 1.5% at room temperature), and a wide-ranging temperature behaviour that meets the X8R dielectric standards (ΔC/C_25°C < ±15%). The maximum dielectric breakdown strength of Method-B samples reached ~131 kVcm, while the energy storage density was ~0.726 J/cm³ at a maximum efficiency of ~80% at 1100 °C. Thus, exhibiting good potentials for balancing temperature stability with energy storage applications.     

Tetrazole tethered polymers for alkaline anion exchange membranes

Poly(2,6-dimethyl-1,4-phenylene oxide) was tethered with a 1,5-disubstituted tetrazole through a quaternary ammonium linkage. The formation of a tetrazole-ion network in the resulting polymers was found to promote the hydroxide ion transport through the Grotthus-type mechanism.

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Defect structure evolution and electrical properties of BaTiO3-based ferroelectric ceramics

Relaxor perovskite ferroelectric 0.1Bi(Zn_1/2Zr_1/2)O₃-0.9BaTiO₃(0.1BZZ-0.9BT) ceramics were successfully prepared, whose powders synthesized by the sol-gel process, with average grain size about 1.29 μm. 1.75 J/cm³ discharge energy density and good dielectric stability were obtained over a wide temperature range from 25°C to 140°C. The pulse discharge capability of 0.1BZZ-0.9BT ceramics was tested under different electric fields. The discharge time was 2.13 μs, which proved its ability to charge and discharge quickly. Complex impedance analysis and thermally stimulated depolarization current tests were applied to investigate the defect types and activation of 0.1BZZ-0.9BT ceramics. The evolution process of composite defects and oxygen vacancies profoundly affects the dielectric temperature stability of 0.1BZZ-0.9BT ceramics’ energy storage property.     

Novel Redox-Dependent Esterase Activity (EC 3.1.1.2) for DJ-1: Implications for Parkinson’s Disease

Mutations the in human DJ-1 (hDJ-1) gene are associated with early-onset autosomal recessive forms of Parkinson’s disease (PD). hDJ-1/parkinsonism associated deglycase (PARK7) is a cytoprotective multi-functional protein that contains a conserved cysteine-protease domain. Given that cysteine-proteases can act on both amide and ester substrates, we surmised that hDJ-1 possessed cysteine-mediated esterase activity. To test this hypothesis, hDJ-1 was overexpressed, purified and tested for activity towards 4-nitrophenyl acetate (pNPA) as µmol of pNPA hydrolyzed/min/mg·protein (U/mg protein). hDJ-1 showed maximum reaction velocity esterase activity (V_max = 235.10 ± 12.00 U/mg protein), with a sigmoidal fit (S_0.5 = 0.55 ± 0.040 mM) and apparent positive cooperativity (Hill coefficient of 2.05 ± 0.28). A PD-associated mutant of DJ-1 (M26I) lacked activity. Unlike its protease activity which is inactivated by reactive oxygen species (ROS), esterase activity of hDJ-1 is enhanced upon exposure to low concentrations of hydrogen peroxide (<10 µM) and plateaus at elevated concentrations (>100 µM) suggesting that its activity is resistant to oxidative stress. Esterase activity of DJ-1 requires oxidation of catalytic cysteines, as chemically protecting cysteines blocked its activity whereas an oxido-mimetic mutant of DJ-1 (C106D) exhibited robust esterase activity. Molecular docking studies suggest that C106 and L126 within its catalytic site interact with esterase substrates. Overall, our data show that hDJ-1 contains intrinsic redox-sensitive esterase activity that is abolished in a PD-associated mutant form of the hDJ-1 protein.     

Branched Polyvinyl Alcohol Hybrid Membrane for Acid Recovery via Diffusion Dialysis

A branched polymer was prepared by grafting allyltrimethylammonium chloride onto polyvinyl alcohol (PVA) via free‐radical polymerization. Afterwards, a series of hybrid membranes were prepared by sol‐gel cross‐linking between quaternary ammonium‐PVA and tetraethoxysilane. The obtained membranes were characterized in terms of infrared spectroscopy, ion exchange capacity, water uptake, linear expansion ratio, and acid resistance. The thermal properties of the membranes were investigated as well. The diffusion dialysis performances of the membranes were tested by using a simulated feed solution containing HCl and FeCl₂. The diffusion dialysis coefficients and the separation factors were much better than those of the commercial DF‐120 membrane.