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.     

Learning from Examples with Information Theoretic Criteria

This paper discusses a framework for learning based on information theoretic criteria. A novel algorithm based on Renyi's quadratic entropy is used to train, directly from a data set, linear or nonlinear mappers for entropy maximization or minimization. We provide an intriguing analogy between the computation and an information potential measuring the interactions among the data samples. We also propose two approximations to the Kulback-Leibler divergence based on quadratic distances (Cauchy-Schwartz inequality and Euclidean distance). These distances can still be computed using the information potential. We test the newly proposed distances in blind source separation (unsupervised learning) and in feature extraction for classification (supervised learning). In blind source separation our algorithm is capable of separating instantaneously mixed sources, and for classification the performance of our classifier is comparable to the support vector machines (SVMs).     

Ultralow oil-water IFTs using neutralized oxidized hydrocarbons as surfactants

Surfactants that may be suitable for application in enhanced oil recovery have been produced from C₂₂ and C₂₆ paraffinic and naphthenic petroleum fractions by a two-step process. The hydrocarbon feed stocks were first oxidized in the vapor-phase, followed by neutralization of the oxidized products with aqueous alkali. As a result, dilute solutions of organic acid salts were produced that achieved ultralow (<10⁻² dyne/cm) interfacial tensions against a synthetic oil. Surfactant solutions that exhibited the lowest interfacial tensions (IFTs) were prepared from neutralizations that used low concentrations of sodium hydroxide rather than sodium silicate, sodium tripolyphosphate, or sodium carbonate. Neutralizations that used sodium silicate or sodium carbonate resulted in surfactant solutions having IFT profiles that were less sensitive to the electrolyte concentration. When sodium hydroxide was combined with either sodium silicate or sodium tripolyphosphate in the neutralizations, solutions having intermediate IFT properties were produced. The amount of alkali used in the neutralizations was observed to affect the IFT properties of the resultant surfactant solution. The electrolyte concentration at which the minimum IFT occurred was inversely related to the pH of the surfactant solution. For surfactant solutions of common pH prepared from different concentrations of oxidized product, the minimum IFTs all occurred at the same concentration of electrolyte. Surfactant solutions remained interfacially active even in the presence of significant concentrations of calcium chloride. One pore volume of a solution containing only about 1% of active surfactant recovered 42.0% of the residual oil in a tertiary core-flood experiment.     

Thermally Stimulated Polarization and Depolarization in Halogen-Containing Lead Silicate Glasses

Thermally stimulated polarization and depolarization current (TSPC/TSDC) measurements were made on lead halide silicate glasses having compositions (65 − x )PbO· x PbX₂·35SiO₂ where x = 0, 0.1, 2, 10 and X = F, CI, Br, and I. The addition of halogen ions to lead silicate glasses gives rise to a new high-temperature TSDC peak in the vicinity of the peak previously observed in binary lead silicate glasses. The integrated area of the new peak is dependent on the amount and type of halogen ion present in the glass and does not saturate in the temperature range of our measurements. This new peak is attributed to space charge polarization of halogen ions.     

An evaluation of the soxtec system for oil determination in soybeans

The Soxtec System and the AOCS method were compared for oil determination in soybeans, and no significant difference was found between the two methods. The Root Mean Square Error (RMSE) and standard deviation for individual samples were higher for the Soxtec, but this was attributable to the regrinding step used. The study suggests that the Soxtec System is faster and just as accurate as the AOCS method.     

Additional modules for versatile and economical PCR-based gene deletion and modification in Saccharomyces cerevisiae

An important recent advance in the functional analysis of Saccharomyces cerevisiae genes is the development of the one-step PCR-mediated technique for deletion and modification of chromosomal genes. This method allows very rapid gene manipulations without requiring plasmid clones of the gene of interest. We describe here a new set of plasmids that serve as templates for the PCR synthesis of fragments that allow a variety of gene modifications. Using as selectable marker the S. cerevisiae TRP1 gene or modules containing the heterologous Schizosaccharomyces pombe his5⁺ or Escherichia coli kan^r gene, these plasmids allow gene deletion, gene overexpression (using the regulatable GAL1 promoter), C- or N-terminal protein tagging [with GFP(S65T), GST, or the 3HA or 13Myc epitope], and partial N- or C-terminal deletions (with or without concomitant protein tagging). Because of the modular nature of the plasmids, they allow efficient and economical use of a small number of PCR primers for a wide variety of gene manipulations. Thus, these plasmids should further facilitate the rapid analysis of gene function in S. cerevisiae. © 1998 John Wiley & Sons, Ltd.     

Flavor Fade in Peanuts During Short-term Storage

ABSTRACT: Flavor characteristics of roasted peanuts over short-term storage were explored through sensory and chemical analyses. The volatiles from freshly roasted peanuts were evaluated over short-time (21 d) storage using gas chromatography, chemosensory techniques, and a sensory panel to quantify and identify pyrazines and hexanal over a 21-d storage period. A significant decrease ( P < 0.05) was noted in 2,3-diethylpyrazine, 2-methoxypyrazine, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine, and 2,3,5-trimethylpyrazine concentrations over a 21-d period. No significant difference ( P > 0.05) was noted in the 2-methylpyrazine and 2-ethylpyrazine concentrations. The hexanal concentration significantly increased ( P < 0.05) over the 21-d period. The peroxide values and sensory analysis agreed with these results. A significant increase ( P < 0.05) in peroxide value was seen at days 14 and 21, and a significant decrease ( P < 0.05) in fresh roasted peanuty flavor from day 0 to 21 and significant increases ( P < 0.05) in painty, cardboardy, and bitter flavors from day 7 to 21 with the sensory analysis. The electronic nose successfully separated day 0 and 21 samples from day 7 and 14 samples, which were also separated but with some overlap.     

Sorption of Ethyl Butyrate and Octanal Constituents of Orange Essence by Polymeric Adsorbents

Sorption characteristics, rates and capacities of polymeric adsorbents (XAD-4, XAD-7, XAD-16, Duolite ES-865, Duolite S-761, Porapak-Q and XUS-43436) for ethyl butyrate and octanal were determined using model solutions. Sorption of these two principal components of aqueous orange essence, was evaluated utilizing the Freundlich isotherm model. Breakthrough curves were determined using XAD-16 as adsorbent. The capacity of XAD-16 for ethyl butyrate in the column system was 426±212 mg/g. There was no column breakthrough for octanal even after 130 bed volumes. Most (91.4%) of the adsorbed ethyl butyrate was eluted from XAD-16 resin by 95% ethanol elution. Recovery of adsorbed octanal from the resin was 66.4%.