Complexity classes for self-assembling flexible tiles

We present a theoretical model for self-assembling DNA tiles with flexible branches. We encode an instance of a “problem” as a pot of such tiles for which a “solution” is an assembled complete complex without any free sticky ends. Using the number of tiles in an assembled complex as a measure of complexity we show how NTIME classes (such as NP and NEXP) can be represented with corresponding classes of the model.     

Non-linear impulsive dynamical systems. Part II: Stability of feedback interconnections and optimality

In a companion paper (Nonlinear Impulsive Dynamical Systems. Part I: Stability and Dissipativity) Lyapunov and invariant set stability theorems and dissipativity theory were developed for non-linear impulsive dynamical systems. In this paper we build on these results to develop general stability criteria for feedback interconnections of non-linear impulsive systems. In addition, a unified framework for hybrid feedback optimal and inverse optimal control involving a hybrid non-linear-non-quadratic performance functional is developed. It is shown that the hybrid cost functional can be evaluated in closed-form as long as the cost functional considered is related in a specific way to an underlying Lyapunov function that guarantees asymptotic stability of the non-linear closed-loop impulsive system. Furthermore, the Lyapunov function is shown to be a solution of a steady-state, hybrid Hamilton‐Jacobi‐Bellman equation.     

The stress stability of olanzapine: studies of interactions with excipients in solid state pharmaceutical formulations

Stress stability testing represents an important part of the drug development process. It is used as an important tool for the identification of degradation products and degradation pathways, as well as for the assessment of changes in physical form of drug molecules. The impact of excipients on the stability of olanzapine confirms that levels of impurities and degradants are limiting parameters and are therefore used for stability evaluation. The major degradation product of olanzapine was identified as 2-methyl-5,10-dihydro-4H-thieno[2,3-b][1,5]benzodiazepine-4-one (III). The structure of III was determined by using LC-MS, IR and NMR. Compatibility and stress stability results demonstrated that tablet formulations of olanzapine are sensitive to temperature and moisture. In samples protected from moisture, the increase in concentration of III was shown to be highly temperature dependent and the degradation followed zero-order kinetics. In addition, studies of olanzapine with excipients and in formulated tablets revealed polymorphic phase changes in some samples, influenced by a combination of stress temperature and humidity conditions. Polymorphic transitions were monitored using x-ray powder diffraction (XRPD) analysis and exhibited no correlation between the phase change (appearance of a new polymorph) and the degradation process.     

Linearisation of asymmetrical Doherty amplifier by the even-order non-linear signals

This paper considers the linearisation of an asymmetrical two-way Doherty amplifier by the method that uses the second harmonics and fourth-order non-linear signals for linearisation. These even-order signals for linearisation are extracted at the output of the peaking amplifier, adjusted in amplitude and phase and injected at the input and output of the carrier amplifier transistor in the Doherty configuration. The effect of linearisation has been experimentally confirmed on a fabricated asymmetrical Doherty amplifier with the additional circuit for linearisation. The suppression of the third-order intermodulation products has been carried out for two-tone test, 64QAM and WCDMA digitally modulated signals in a range of signal power.     

Dietary Supplementation with 22-<Emphasis Type="Italic">S</Emphasis>-Hydroxycholesterol to Rats Reduces Body Weight Gain and the Accumulation of Liver Triacylglycerol

This study explores the pharmacokinetics of 22-S-hydroxycholesterol (22SHC) in vivo in rats. We also carried out a metabolic study to explore whether the beneficial effects observed of 22SHC on glucose and lipid metabolism in vitro could be seen in vivo in rats. In the pharmacokinetic study, rats were given 50 mg/kg of [³H]22-S-hydroxycholesterol before absorption, distribution and excretion were monitored. In the metabolic study, the effect of 22SHC (30 mg/kg/day for 3 weeks) in rats on body weight gain [chow and high-fat diet (HFD)], serum lipids triacylglycerol (TAG) content and gene expression in liver and skeletal muscle were examined. Results showed that 22SHC was well absorbed after oral administration and distributed to most organs and mainly excreted in feces. Rats receiving 22SHC gained less body weight than their controls regardless whether the animals received chow diet or HFD. Moreover, we observed that animals receiving HFD had elevated levels of serum TAG while this was not observed for animals on HFD supplemented with 22SHC. The amount of TAG in liver was reduced after 22SHC treatment in animals receiving either chow diet or HFD. Gene expression analysis revealed that two genes (carnitine palmitoyltransferase 2 and uncoupling protein 3) involved in fatty acid oxidation and energy dissipation were increased in liver. Ucp3 expression (both protein and mRNA level) was increased in skeletal muscle, but insulin-stimulated glucose uptake and TAG content were unchanged. In conclusion, 22SHC seems to be an interesting model substance in the search of treatments for disorders involving aberrations in lipid metabolism.     

Mechanochemical and Low‐Temperature Synthesis of Nanocrystalline Fluorohydroxyapatite/Fluorapatite

Low‐temperature synthesis of fluorapatite/fluorohydroxyapatite with precursor mixture previously mechanochemically treated is described in this article. Ethylene vinylacetate/versatate copolymer as a surface active substance was mechanically treated to obtain a core‐shell system with strongly controlled grain size. Despite usual behavior of mechanically activated systems, only an amorphous phase formed from precursor ions present in the mixture composed of β‐Ca₂P₂O₇, CaCO₃, CaF₂, and unreacted Ca(OH)₂ was obtained during milling for 5 min to 8 h. The mixture contained depots of labile F^? ions conserved in micelles cages, which are useful for teeth protection from carries. For transformation of these amorphous phases into fluorapatite, an additional low thermal treatment was necessary. The mechanism of the precursor mixture transformation into fluorapatite during milling and thermal treatment was investigated using FTIR spectroscopy and X‐ray diffraction. The morphology and size distribution of the obtained powders was studied using SEM and TEM.     

Development of green extraction process to produce antioxidant-rich extracts from purple coneflower

The present study was conducted to develop subcritical water extraction (SWE) of Echinacea purpurea flowers. The influence of temperature and extraction time on quality of extracts considering total phenols content, total flavonoids content, antioxidant capacity and extraction yield, was determined. Optimized extraction parameters for maximised investigated responses were as follows: 147.56 °C and 8.43 min. The experimental values agreed with the values predicted, thus indicating the adequacy of central composite experimental design for modelling the SWE of bioactive compounds from E. purpurea. Results of the study also highlighted the potential application of E. purpurea subcritical water extracts as a source of valuable bioactive compounds.