Discrete-time analysis of linear and nonlinear systems using analogcircuit simulators

A method to teach discrete-time systems analysis concepts and skills to engineering students is presented and discussed. The method presented in this investigation uses commercially available analog-digital circuit simulators and a delay element and sampler constructed from analog components. The delay element and sampler used with standard, continuous-time amplifiers and summers, allow the user to simulate discrete-time systems in a manner identical to that used for continuous-time systems. Construction of the discrete-time delay element and sampler using the PSpice circuit simulator is presented as is their use in a variety of well-known linear discrete-time systems including problems from economics, population dynamics and digital signal processing. The well-known nonlinear quadratic model of chaos is also simulated in this investigation. The results of the linear and nonlinear discrete-time system analysis are compared to the analytical results and show that the delay element and sampler are stable and accurate components useful in modeling a wide variety of linear and nonlinear discrete-time systems     

Luminescent Conjugated Oligothiophenes for Sensitive Fluorescent Assignment of Protein Inclusion Bodies

Small hydrophobic ligands identifying intracellular protein deposits are of great interest, as protein inclusion bodies are the pathological hallmark of several degenerative diseases. Here we report that fluorescent amyloid ligands, termed luminescent conjugated oligothiophenes (LCOs), rapidly and with high sensitivity detect protein inclusion bodies in skeletal muscle tissue from patients with sporadic inclusion body myositis (s‐IBM). LCOs having a conjugated backbone of at least five thiophene units emitted strong fluorescence upon binding, and showed co‐localization with proteins reported to accumulate in s‐IBM protein inclusion bodies. Compared with conventional amyloid ligands, LCOs identified a larger fraction of immunopositive inclusion bodies. When the conjugated thiophene backbone was extended with terminal carboxyl groups, the LCO revealed striking spectral differences between distinct protein inclusion bodies. We conclude that 1) LCOs are sensitive, rapid and powerful tools for identifying protein inclusion bodies and 2) LCOs identify a wider range of protein inclusion bodies than conventional amyloid ligands.     

Organic–Inorganic Hybrid Films Based on Hydroxylated Soybean Oils

Hybrid organic–inorganic films were prepared using four different hydroxylated soybean oils (HSO) or epoxidized soybean oil as organic precursor and tetraethyl orthosilicate (TEOS) as inorganic precursor in a mass ratio of HSO:TEOS of 90:10. The films were macroscopically homogeneous and were characterized by swelling and extraction in solvent, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) including energy dispersive spectroscopy (EDX), adhesion and hardness. Their properties varied as a function of the number of OH groups present in the HSO. The best hybrid system was HSOF198/TEOS, with an OH value of 198 mg of KOH/g, which presents lower swelling coefficient, very good adhesion on aluminium surface and good hardness.     

The microflora of Tilsit cheese. Part 1. Variability of the smear flora

The microflora of 25 Tilsit cheeses from 2 cheese plants was analysed. Debaryomyces hansenii was found to be the predominant yeast in all stages of ripening. 75–95% of the bacterial flora consisted of coryneform bacteria. Several of the isolates were identified as Arthrobacter. Brevibacterium linens was found at 0-15%. In all cheeses tested, 5-15% of total cell counts were made up by staphylococci. They were determined as being not Staphylococcus aureus or other pathogenic staphylococci since all isolates were negative with respect to thermo-nuclease, clumping, coagulase, and hemagglutination. Most of the isolates were hemolysis negative. By genetical analysis, several selected isolates were classified as Staphylococcus equorum, one isolate as S. sciuri. Contamination of cheeses with Fusarium moulds indicated the influence of the smearing strategy on spreading of undesirable microorganisms. In plant A, old cheeses were smeared first, then young cheeses were smeared with the same smear liquid. Fusarium contamination could be detected in all stages of ripening. In plant B, young cheeses (0-3 weeks) were smeared with a commercial surface starter cocktail. In all cheeses of this age, problems with Penicillium contaminations were observed. Older cheeses (>3 weeks) were smeared according to the strategy applied in plant A. Consequently, Fusarium moulds were detected in cheeses 4-8 weeks of age.     

State-of-the-art insulator and electrode materials for use in highcurrent high energy switching

An investigation into the failure of ceramic insulators that are used in a surface discharge switch (SDS) was conducted. The materials analyzed are Al₂O₃-25% SiC, MTF (modified alumina titanate), and CZA 500 (zirconia-alumina composite) ceramics. These insulators were subjected to high-current (~300 kA) surface discharges in atmospheric air and nitrogen. Energy-dispersive X-ray surface analysis was performed on the insulator surfaces in order to determine the contaminants that are present and the possible failure modes associated with the plasma arc environments mentioned above. Electrode erosion rates have been measured as a function of total charge transfer (up to 50 C/shot) for several in-situ materials including Cu-Nb, Cu-Nb+LaB₆, and Cu-Ta. Results from comparisons with standard Cu and CuW materials indicate that the in-situ materials represent an efficient method of retaining the copper in the bulk until it vaporizes and thus yield significantly lower erosion rates at high Coulomb transfer rates     

Economic evaluation of energy conservation projects with an emphasis on initiation time

A procedure for assessing the economic viability of an energy conservation project integrated with building installation has been investigated in previous works. In the present work, a method is developed for economic evaluation of energy conservation projects, which may initiate independence of building construction. A model for optimization of the initiation time has been developed, and the conditions to determine economic feasibility are derived. It was found that the break-even value of the annual energy saved for $1 investment may significantly increase with even a moderate decrease in the expected real investment cost. This break-even value is always greater than the corresponding one found in the building integrated case. The difference increased with an increase in expected fuel inflation rate and also with a decrease in expected investment cost.     

The Reactivity of Difluorocarbene with Hydroxylamines: Synthesis of Carbamoyl Fluorides

Carbamoyl fluorides are formed in reactions of hydroxylamines with difluorocarbene generated from sodium bromodifluoroacetate as readily available and non‐toxic carbene precursor. The process shows a high functional group tolerance, and the reaction path has been rationalized by computational calculations.