DDFSGEN

This paper presents a functional compiler for the automatic design of Direct Digital Frequency Synthesizer (DDFS) integrated circuits (ICs) using a ROM based table look-up architecture. The compiler allows the user to specify high-level specifications such as the acceptable spurious response and it generates the IC architecture, floorplan, and layout. To construct the layout for different specifications, a library of parameterized macrocells has been developed in 1.2 m CMOS technology.A test chip with a quadrature DDFS module has been generated, using the compiler, and fabricated. The chip has two input signals: one is for frequency control while the other is for phase initialization. Input and output word lengths are 16 bits and 6 bits respectively. The chip complexity is approximately 12,000 transistors (DDFS core) and the die size is 4.8×2.9mm ². A maximum sample rate of 80 MHz has been attained implying a maximum sine (cosine) output frequency of 40 MHz and a frequency resolution of 1.22 kHz. The maximum spurious level measured is –46 dB.     

Amorphous Boron Nitride: A Universal,Ultrathin Dielectric For 2D Nanoelectronics

Next‐generation nanoelectronics based on 2D materials ideally will require reliable, flexible, transparent, and versatile dielectrics for transistor gate barriers, environmental passivation layers, capacitor spacers, and other device elements. Ultrathin amorphous boron nitride of thicknesses from 2 to 17 nm, described in this work, may offer these attributes, as the material is demonstrated to be universal in structure and stoichiometric chemistry on numerous substrates including flexible polydimethylsiloxane, amorphous silicon dioxide, crystalline Al₂O₃, other 2D materials including graphene, 2D MoS₂, and conducting metals and metal foils. The versatile, large area pulsed laser deposition growth technique is performed at temperatures less than 200 °C and without modifying processing conditions, allowing for seamless integration into 2D device architectures. A device‐scale dielectric constant of 5.9 ± 0.65 at 1 kHz, breakdown voltage of 9.8 ± 1.0 MV cm^?1, and bandgap of 4.5 eV were measured for various thicknesses of the ultrathin a‐BN material, representing values higher than previously reported chemical vapor deposited h‐BN and nearing single crystal h‐BN.     

Modeling and simulation of 2D lithium‐ion solid state battery

The goal of the work presented here was to develop a simulation approach for studying the effects of materials and geometry on the performance of Li‐ion Solid State Batteries (SSB). Simulation provides the opportunity to explore, with ease, different material properties and cell geometries to optimize a Li‐ion SSB's performance. Simulations shown in this paper are time‐dependent and consider electrochemical reaction, heat transfer, the diffusion of Li‐ions and electrons in the electrolyte, and solid Li diffusion in the positive electrode. A 2D model was simulated and the results shown. The simulations were able to show discharge curves, heat flux, the concentration of Li‐ions, electrons, and solid Li at any time in the discharge cycle. Copyright © 2015 John Wiley & Sons, Ltd.     

Site-directed mutagenesis of Arg60 and Cys271 in ornithine transcarbamylase from rat liver

We have investigated the putative carbamylphosphate- and ornithine-bindingdomains in ornithine transcarbamylase from rat liver using site-directedmutagenesis. Arg60, present in the phosphate-binding motif X-Ser-X-Arg-Xand therefore implicated in the binding of the phosphate moietyof carbamylphosphate has been replaced with a leucine. Thisresults in a dramatic reduction of catalytic activity, althoughthe enzyme is synthesized in cells stably transfected with themutant clone and imported, correctly processed and assembledinto a homotrimer in mitochondria. The sole cysteine residue(Cys271) has been implicated in ornithine binding by the chemicalmodification studies of Marshall and Cohen in 1972 and 1980(J. Biol. Chem., 247, 1654–1668, 1669–1682; 255,7291–7295, 7296–7300). Replacement of this residuewith serine did not eliminate enzyme activity but affected theMichaelis constant for ornithine (K_b, increasing it 5-fold from0.71 to 3.7 mM and reduced the k_cat at pH 8.5 by 20-fold. Thesechanges represent a loss in apparent binding energy for theenzyme - ornithine complex of 2.9 kcal/mol, suggesting thatCys271 is normally involved in hydrogen bonding to the substrate,ornithine. The cysteine to serine substitution also caused thedissociation constant (Kä for the competitive inhibitor,L-norvaline to be increased 10-fold, from 12 to 120 µM.The small loss in binding energy and relatively high residualcatalytic activity of the mutant strongly suggests that a numberof other residues are involved in the binding of ornithine.The effect of replacement of Cys271 with serine was restrictedto the ornithine binding site of the enzyme since both the bindingconstant for carbamyl-phosphate (K_ia) and Michaelis constant(K_a) were not appreciably different for mutant and wild-typeenzymes. The pH optimum of the wild-type enzyme (8.6) is increasedto > 9.6 in the Ser271 mutant.     

Design of a positive resist for projection lithography in the mid-UV

The design, synthesis, formulation, and process optimization of a new mid-UV resist are described. The synthesis of a spectrally matched sensitizer was guided by semiempirical quantum mechanical calculations that predict the effect of structural changes on optical absorption characteristics. The formulation was guided by computer profile simulation studies and the process development by a response surface analytical procedure. These techniques allowed formulation optimization to be achieved on the basis of an understanding of the complex interactions between the resist dissolution response functions and the modulation transfer function of the exposure tool for which the resist was designed.     

The effect of aging and pH on Pb(II) sorption processes at the calcite-water interface

The effect of aging on Pb(II) retention in 1 microM Pb, calcite suspensions at pH 7.3, 8.2, and 9.4, under room-temperature conditions, was explored via a combination of batch sorption-desorption experiments and X-ray absorption spectroscopy (XAS). Short-term experiments, up to 12 days, reveal the predominance of an adsorption mechanism at pH 8.2, as confirmed by XAS analysis. Linear-combination fitting of XANES spectra indicates a dual sorption mechanism, with approximately 95% adsorbed and appromicately 5% coprecipitated, and approcimately 75% adsorbed and approsimately 25% coprecipitated Pb at pH 7.3 and 9.4, respectively. For long-term sorption, 60-270 days, slow continuous uptake occurs at pH 7.3 and 8.2, determined by EXAFS to be due to an adsorption mechanism. At pH 9.4, no further uptake occurs with aging, and the solid-phase distribution of Pb is commensurate with that for short-term experiments, suggesting that coprecipitated metal may alterthe calcite surface precluding further Pb sorption. Desorption experiments indicate that at pH 7.3 and 8.2 long-term sorption products-constituted primarily of Pb inner-sphere adsorption complexes-are reversibly bound. For aged pH 9.4 samples, significant sorption irreversibility indicates that the coprecipitated component is not readily exchangeable with the aqueous phase, and thus coprecipitation may be effective for long-term metal sequestration.     

Effects of baking on cyanidin-3-glucoside content and antioxidant properties of black and yellow soybean crackers

Black soybean is a potential functional food ingredient with high anthocyanin content, but the ability to maintain anthocyanin content under dry heat processing has not been reported. This study investigated the effects of soybean seed coat colour and baking time–temperature combinations on the extractable antioxidant properties of a soy cracker food model. Crackers prepared with black soybeans had significantly higher TPC, total isoflavones, and peroxyl, hydroxyl, and ABTS⁺ radical scavenging abilities than their yellow counterparts, at all time–temperature combinations. Cyanidin-3-glucoside (C3G) was detected only in black soybean crackers, and all baking treatments significantly decreased C3G. The greatest losses occurred at the low temperature × long time and high temperature × short time, the smallest loss with moderate temperature × short/medium time. The high temperature treatment altered phenolic acid and isoflavone profiles; however, total isoflavones were unaffected. Overall results suggest that moderate baking temperature at minimal time may best preserve anthocyanin and other phenolics in baked black soybean crackers.     

Effect of hydroxycinnamic acids on lipid oxidation and protein changes as well as water holding capacity in frozen minced horse mackerel white muscle

The antioxidant effectiveness of different hydroxycinnamic acids for inhibiting the formation of off-flavours associated to rancidity in minced frozen horse mackerel white muscle stored at −10 and −18 °C was studied. The influence of lipid oxidation on protein aggregation, protein denaturation and water holding capacity was also determined. Caffeic acid, o-coumaric acid and ferulic acid were the antioxidants tested. The order of antioxidant effectiveness was caffeic acid > ferulic acid > o-coumaric acid accordingly with previous results obtained in chilled horse mackerel. A strong dependence of antioxidant effectiveness to the ratio lipid/antioxidant concentration was observed. There was no evidence to suggest that antioxidants reduce protein aggregation or water holding capacity changes. Protein aggregation was not accompanied by gross protein denaturation, as monitored by differential scanning calorimetry. No evidence was found for a link between extent of lipid oxidation and degree of protein aggregation or water holding capacity changes.     

Chemical beneficiation of coal with aqueous hydrogen peroxide/sulphuric acid solutions

The removal of sulphur and ash from coal treated with aqueous hydrogen peroxide/sulphuric acid solutions has been studied at ambient temperature, under a variety of experimental conditions. Almost complete elimination of the sulphate and the pyritic sulphur was observed in most cases, as well as substantial reduction in the ash content. The other components of the organic coal matrix were not affected to a significant extent, indicating high selectivity of the $\text{H}{}_2\text{O}{}_2\text{H}{}_2\text{SO4}$ system towards sulphur oxidation. An optimal H₂SO₄ concentration was established, above which the acid was found to have an adverse effect on the oxidation of pyrite by hydrogen peroxide.