An efficient nonlinear circuit simulation technique

This paper proposes a novel method for the analysis and simulation of integrated circuits (ICs) with the potential to greatly shorten the IC design cycle. The circuits are assumed to be subjected to input signals that have widely separated rates of variation, e.g., in communication systems, an RF carrier modulated by a low-frequency information signal. The proposed technique involves two stages. Initially, a particular order result for the circuit response is obtained using a multiresolution collocation scheme involving cubic spline wavelet decomposition. A more accurate solution is then obtained by adding another layer to the wavelet series approximation. However, the novel technique presented here enables the reuse of results acquired in the first stage to obtain the second-stage result. Therefore, vast gains in efficiency are obtained. Furthermore, a nonlinear model-order reduction technique can readily be used in both stages making the calculations even more efficient. Results will highlight the efficacy of the proposed approach     

Expression of type 2 11beta-hydroxysteroid dehydrogenase and corticosteroid hormone receptors in early human fetal life

In adult life, the type 2 isozyme of 11beta-hydroxysteroid dehydrogenase (11betaHSD2) protects the mineralocorticoid receptor (MR) from glucocorticoid by inactivating cortisol to cortisone. 11betaHSD2 activity has been reported in human fetal tissues, where glucocorticoids may impair fetal growth yet are also required for normal fetal development. Using digoxigenin-labeled complementary ribonucleic acid (RNA) probes and an in-house 11betaHSD2 antiserum, we have analyzed the expression of 11betaHSD2, MR, and glucocorticoid receptor (GR) in human fetal tissues of gestational age 6-17 weeks (n=15). 11BetaHSD2 expression was absent at gestational age 6+ weeks, but was expressed in abundance in many fetal tissues between 8-12 weeks. At this time, 11betaHSD2 colocalized with GR messenger RNA (mRNA) expression in metanephros, gut, muscle, spinal cord and dorsal root ganglia, periderm, sex chords of testis, and adrenal. In particular within fetal kidney, intense expression of 11betaHSD2 and GR mRNA was observed over Bowman's capsule and the vascular tufts of developing glomeruli as they migrated from the surface of the kidney to the inner cortex. Only lung and adrenal medullary rests demonstrated high levels of GR mRNA but low levels of 11betaHSD2. 11BetaHSD2 mRNA and immunoreactivity staining patterns were similar, with the exception of the fetal adrenal, where mRNA was localized to the outer definitive zone but immunoreactivity was localized to the inner fetal zone. Colocalization of 11betaHSD2 (and GR mRNA) with MR mRNA was observed principally within epithelial cells of collecting ducts, particularly after 16 weeks gestation when the pattern of distribution of 11betaHSD2 became more adult in nature. High levels of MR mRNA were observed within developing bone. The data indicate that 11betaHSD2 in fetal life principally modulates ligand access to the GR in most fetal tissues, notably glomeruli and tubules in the developing kidney, testis, and periderm, and this may be have ramifications for fetal sodium homeostasis and differentiation. The development of tissues previously shown to have a critical requirement for glucocorticoids, such as lung and adrenal medulla, is facilitated by the expression of GR mRNA, but not 11betaHSD2. The expression of MR mRNA in high abundance in bone suggests a role for corticosteroids in human bone development, and the low/absent expression of 11betaHSD2 at this site suggests that it is functionally acting as a GR.     

Asymptotic solvers for second-order differential equation systems with multiple frequencies

In this paper, an asymptotic expansion is constructed to solve second-order differential equation systems with highly oscillatory forcing terms involving multiple frequencies. An asymptotic expansion is derived in inverse of powers of the oscillatory parameter and its truncation results in a very effective method of dicretizing the differential equation system in question. Numerical experiments illustrate the effectiveness of the asymptotic method in contrast to the standard Runge–Kutta method.     

Fabricating Strong and Stiff Bioplastics from Whole Spirulina Cells

Since the 1950s, 8.3 billion tonnes (Bt) of virgin plastics have been produced, of which around 5 Bt have accumulated as waste in oceans and other natural environments, posing severe threats to entire ecosystems. The need for sustainable bio-based alternatives to traditional petroleum-derived plastics is evident. Bioplastics produced from unprocessed biological materials have thus far suffered from heterogeneous and non-cohesive morphologies, which lead to weak mechanical properties and lack of processability, hindering their industrial integration. Here, a fast, simple, and scalable process is presented to transform raw microalgae into a self-bonded, recyclable, and backyard-compostable bioplastic with attractive mechanical properties surpassing those of other biobased plastics such as thermoplastic starch. Upon hot-pressing, the abundant and photosynthetic algae spirulina forms cohesive bioplastics with flexural modulus and strength in the range 3–5 GPa and 25.5–57 MPa, respectively, depending on pre-processing conditions and the addition of nanofillers. The machinability of these bioplastics, along with self-extinguishing properties, make them promising candidates for consumer plastics. Mechanical recycling and fast biodegradation in soil are demonstrated as end-of-life options. Finally, the environmental impacts are discussed in terms of global warming potential, highlighting the benefits of using a carbon-negative feedstock such as spirulina to fabricate plastics.     

Algorithms for testing that sets of DNA words concatenate without secondary structure

We present an efficient algorithm for determining whether all moleculesin a combinatorial set of DNA or RNA strandsare structure free, and thus availablefor bonding to their Watson-Crick complements.This work is motivated by the goalof testing whether strands used in DNAcomputations or as molecular bar-codesare structure free, where the strands areconcatenations of short words. We alsopresent an algorithm for determining whetherall words in S*, for some finite setS of equi-length words, are structure free. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fluorescent polyacrylate derivate from 4-biphenylmethanol with UV-green emission

In this paper we report the synthesis of a new polyacrylate named poly(1,1?-BP4MA) which is a derivate from 4-biphenylmethanol monomer. Poly(1,1?-BP4MA) was obtained by solution and bulk polymerization techniques to yield polymers with high molecular weight and high solubility. The study of the optical properties showed that poly(1,1?-BP4MA) is a fluorescent material with emission in the UV-green region and it has similar quantum yield to tryptophan.     

Comparison of Soybean and Cottonseed Oils upon Hydrogenation with Nickel,Palladium and Platinum Catalysts

There is current interest in reducing the trans fatty acids (TFA) in hydrogenated vegetable oils because consumption of foods high in TFA has been linked to increased serum cholesterol content. In the interest of understanding the TFA levels, hydrogenation was carried out in this work on soybean oil and cottonseed oil at two pressures (2 and 5 bar) and 100 °C using commercially available Ni, Pd, and Pt catalysts. The TFA levels and the fatty acid profiles were analyzed by gas chromatography. The iodine value of interest is ~70 for all-purpose shortening and 95–110 for pourable oil applications. In all cases, higher hydrogen pressures produced lower levels of TFA. In the range of 70–95 iodine values for the hydrogenated products, the Pt catalyst gave the least TFA, followed closely by Ni, and then Pd, for both oils. For all three catalysts at 2- and 5-bar pressures and 70–95 iodine values, cottonseed oil contained noticeably less TFA than soybean oil; this is probably because cottonseed oil contains a lower total amount of olefin-containing fatty acids relative to soybean oil. Approximate kinetic modeling was also done on the hydrogenation data that provided additional confirmation of data consistency.     

Hot metal pretreatment by powder injection of lime‐based reagents

A mathematical model earlier proposed has been improved to predict the kinetics of multicomponent reactions in the hot metal pretreatment through the injection of reactive fluxes. It is assumed that there are two reaction zones along the flux injection operation: a transitory reaction between the rising particles and the bulk metal, and the permanent reaction between the metal and the top slag. A criterion to estimate the fraction of solids which will react with molten iron in a three‐phase jet (gas‐solid‐liquid) was considered; this fraction of solids carries out the transitory reaction. The model also takes into account the thermodynamic changes produced in the metal and slag due to the chemical reactions. Calculated results of the model are in good agreement with experimental results for the desulfurization of hot metal through the injection of CaO‐SiO₂‐CaF₂‐FeO‐Na₂O reagents at 1400 ‐ 1450 °C. Two kinds of hot metal were tested, one with a low carbon mass content of 3 % and the other with a high carbon mass content of 4.5 %.