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Intrinsic dimensionality detection criterion based on Locally Linear Embedding

Meng L., Breitkopf P.

Computer Science

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2018

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Vol. 19 (3)

345--356

EN

In this work, we revisit the Locally Linear Embedding (LLE) algorithm that is widely employed in dimensionality reduction. With a particular interest to the correspondences of the nearest neighbors in the original and embedded spaces, we observe that, when prescribing low-dimensional embedding spaces, LLE remains merely a weight-preserving rather than a neighborhood-preserving algorithm. Thus, we propose a \neighborhood-preserving ratio" criterion to estimate the minimal intrinsic dimensionality required for neighborhood preservation. We validate its efficiency on sets of synthetic data, including S-curve, Swiss roll, and a dataset of grayscale images.

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Optimization of the Control System Parameters with Use of the New Simple Method of the Largest Lyapunov Exponent Estimation

Balcerzak M., Dąbrowski A., Kapitaniak T., Jach A.

Mechanics and Mechanical Engineering

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2013

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Vol. 17, nr 4

225--239

EN

This text covers application of Largest Lapunov Exponent (LLE) as a criterion for control performance assessment (CPA) in a simulated control system. The main task is to find a simple and effective method to search for the best configuration of a controller in a control system. In this context, CPA criterion based on calculation of LLE by means of a new method [3] is compared to classical CPA criteria used in control engineering [1]. Introduction contains references to previous publications on Lyapunov stability. Later on, description of classical criteria for CPA along with formulae is presented. Significance of LLE in control systems is explained. Moreover, new efficient formula for calculation of LLE [3] is shown. In the second part simulation of the control system used for experiment is described. The next part contains results of the simulation in which typical criteria for CPA are compared with criterion based on value of LLE. In the last part results of the experiment are summed up and conclusions are drawn.

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Influence of sample preparation methods on the quantitation of selected tropane alkaloids from herb of Datura innoxia mill. by HPTLC

Oniszczuk A., Waksmundzka-Hajnos M., Gadzikowska M., Podgórski R., Oniszczuk T.

Acta Chromatographica

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2013

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Vol. 25, no. 3

545--554

EN

The aim of our paper was the examination of various procedures of extraction and purification methods on the yield of atropine and scopolamine in Datura innoxia extracts determined by high-performance thin-layer chromatography (HPTLC). In our experiments, the following extraction methods were used: percolation, ultrasound-assisted extraction (USAE) at various temperatures, and microwave-assisted extraction (MASE). The highest extraction yields of atropine and scopolamine were obtained by ultrasound-assisted extraction method and aqueous acetic acid or aqueous tartaric acid used as extractants. Crude extracts of D. innoxia herb were purified by use of various methods: solid-phase extraction-strong cation exchanger (SPE-SCX), SPE-C18, and liquid-liquid extraction (LLE). The best results of purification with satisfactory %RSD values were obtained by liquid-liquid extraction by use of dichloromethane from aqueous crude alkaloid extract alkalized to pH 12. HPTLC was performed on pre-coated plates Kieselgel 60 F254 in horizontal DS chambers by use of mobile phase: methanol-acetone-aqueous ammonia (5:4.5:0.5). The alkaloids’ content was determined in extracts by use of calibration curve method for atropine and scopolamine. Calibration curves were linear in range of 3.0–30 μg for scopolamine (R = 0.9980) and 2.6–26 μg for atropine (R = 0.9923). Limits of detection (LOD) and limits of quantification (LOQ) were 1.12 μg and 3.42 μg per spot for scopolamine and 0.89 μg and 2.82 μg per spot for atropine.

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Effect of sample-preparation methods on the quantification of selected flavonoids in plant materials by high performance liquid chromatography

Waksmundzka-Hajnos M., Wianowska D., Oniszczuk A., Dawidowicz A. L.

Acta Chromatographica

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2008

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Vol. 20, no. 3

475-488

EN

Extraction yield of flavonoids from plant material Sambucus nigra L. inflorescence and Polygonum aviculare herb was determined by use of various methods of liquid-solid extraction - Soxhlet extraction, ultrasonification (USAE), microwave-assisted extraction (MASE), and accelerated solvent extraction (ASE). Methanol was used as extractant. Crude extracts were evaporated to dryness and prepared to achieve fractionation of flavonoids by LLE or SPE. Samples containing the flavonoid fraction were analysed by RP-HPLC. For quantitative purposes the external standard method with a calibration plot for every standard was used. It was found that yield depends first of all on the plant material from which flavonoid fraction was extracted. For Sambucus nigra L. inflorescence the most effective method was exhaustive extraction in a Soxhlet apparatus. For Polygonum aviculare the most effective method was ASE. The best purification method was SPE on C 18adsorbent, which resulted in the highest recoveries and repeatabilities.