University of Natural science

Lublin, Poland

University of Natural science

Lublin, Poland
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Le B.,University of Natural science | Duong H.,University of Dalat | Truong T.,University of Dalat | Fournier-Viger P.,Harbin Institute of Technology
Knowledge and Information Systems | Year: 2017

Mining frequent sequences in sequential databases are highly valuable for many real-life applications. However, in several cases, especially when databases are huge and when low minimum support thresholds are used, the cardinality of the result set can be enormous. Consequently, algorithms for discovering frequent sequences exhibit poor performance, showing an important increase in execution time, memory consumption and storage space usage. To address this issue, researchers have studied the tasks of mining frequent closed and generator sequences, as they provide several benefits when compared to the set of frequent sequences. One of the most important benefits is that the cardinalities of frequent closed and generator sequences are generally much less than the cardinality of frequent sequences. Hence, humans find it more convenient to analyze the information provided by closed and generator sequences. Moreover, it was shown that frequent closed sequences have the advantage of being lossless, and they thus preserve information about the frequency of all frequent subsequences, while generator sequences can provide higher accuracy for sequence classification tasks since they are the smallest patterns that characterize groups of sequences. Besides, frequent closed sequences can be combined with generators to produce non-redundant sequential rules and recover the complete set of frequent sequences and their frequencies. This paper proposes two novel algorithms named FCloSM and FGenSM to mine frequent closed and generator sequences efficiently. These algorithms are based on new pruning conditions called extended early elimination (3E) and early pruning techniques named EPCLO and EPGEN, designed to identify non-closed and non-generator patterns early. Based on these techniques, two local pruning strategies called LPCLO and LPGEN are proposed to eliminate non-closed and non-generator patterns more efficiently at two successive levels of the prefix search tree without performing subsequence relation checking. These theoretical results, which are the basis of FCloSM and FGenSM, are mathematically proved and are shown to be more general than those presented in previous work. Extensive experiments show that FCloSM and FGenSM are one to two orders of magnitude faster than the state-of-the-art algorithms for discovering frequent closed sequences (CloSpan, BIDE, ClaSP and CM-ClaSP) and for mining frequent generators (FEAT, FSGP and VGEN), and that FCloSM and FGenSM consume much less memory. © 2017 Springer-Verlag London

Chen L.,National University of Singapore | Nguyen-Xuan H.,National University of Singapore | Nguyen-Xuan H.,University of Natural science | Nguyen-Thoi T.,National University of Singapore | And 4 more authors.
International Journal for Numerical Methods in Biomedical Engineering | Year: 2010

A generalized gradient smoothing technique and a smoothed bilinear form of Galerkin weak form have been recently proposed by Liu et al. to create a wide class of efficient smoothed point interpolation methods (PIMs) using the background mesh oftriangular cells. In these methods, displacement fields are constructed by polynomial or radial basis shape functions and strains are smoothed over the smoothed domain associated with the nodes or the edges of the triangular cells. This paper summarizes and assesses bound property, convergence rate and computational efficiency for these methods. It is found that: (1) the incorporation of the PIMs with the node-based strain smoothing operation allows us to obtain an upper bound to the exact solution in the strain energy; (2) the incorporation of the PIMs with the edge-based strain smoothing operation using triangular background mesh can produce a solution of 'ultra-accuracy' and 'super-convergence'; (3) the edge-based strain smoothing operation together with the linear interpolation can provide better computational efficiency compared with other smoothed PIMs and the finite element method when the same triangular mesh is used. These conclusions have been examined and confirmed by intensive examples. ©2009 John Wiley & Sons, Ltd.

Pawlak Z.,Tribochemistry Consulting | Pawlak Z.,University of economics | Urbaniak W.,University of economics | Kaldonski T.,Military University of Technology | Styp-Rekowski M.,University of Natural science
Ecological Engineering | Year: 2010

This study concentrates on the investigation of energy and environmental benefits for used oil pertaining to its reuse through: (i) recovering the heating value of used oils in a combustion process and (ii) re-refining of used oil to produce fresh lube oil products. Tests were made with the used oil samples by ICP technique and the results were compared with standard requirements. We have found that the problems could successfully be solved through used oil management practices including collection centers, transporters, and processors by providing encouragement and financial support towards the re-refining industry. The novelty and value of our work lies in the conclusion that reformulation of motor oil results in lower levels of hazardous elements in used oils. © 2010 Elsevier B.V.

Bordas S.P.A.,University of Glasgow | Rabczuk T.,University of Canterbury | Hung N.-X.,University of Natural science | Nguyen V.P.,Technical University of Delft | And 4 more authors.
Computers and Structures | Year: 2010

We present in this paper recent achievements realised on the application of strain smoothing in finite elements and propose suitable extensions to problems with discontinuities and singularities. The numerical results indicate that for 2D and 3D continuum, locking can be avoided. New plate and shell formulations that avoid both shear and membrane locking are also briefly reviewed. The principle is then extended to partition of unity enrichment to simplify numerical integration of discontinuous approximations in the extended finite element method. Examples are presented to test the new elements for problems involving cracks in linear elastic continua and cracked plates. In the latter case, the proposed formulation suppresses locking and yields elements which behave very well, even in the thin plate limit. Two important features of the set of elements presented are their insensitivity to mesh distortion and a lower computational cost than standard finite elements for the same accuracy. These elements are easily implemented in existing codes since they only require the modification of the discretized gradient operator, B. © 2008 Elsevier Ltd. All rights reserved.

Cuong T.D.,Catholic University of Daegu | Hung T.M.,University of Natural Science | Kim J.C.,Korea Research Institute of Chemical Technology | Kim E.H.,Korea Basic Science Institute | And 4 more authors.
Journal of Natural Products | Year: 2012

Four new phenolic compounds, caesalpiniaphenols A-D (1-4), together with eight known compounds were isolated from Caesalpinia sappan heartwood. The chemical structures were established mainly by NMR, MS, ECD, and Mosher's method. Compounds 4, 5, and 7 showed weak inhibitory activity against the LPS-induced NO production in macrophage RAW264.7 cells with IC50 values of 12.2, 3.5, and 5.7 μM, respectively. © 2012 The American Chemical Society and American Society of Pharmacognosy.

Szwajgier D.,University of Natural science
Journal of the Institute of Brewing | Year: 2011

A purified extracellular ferulic acid esterase from Lactobacillus acidophilus K1 was successfully used during mashing for the release of free phenolic acids into sweet wort. The enzyme was produced in bioreactors and partially purified to obtain the monoenzyme preparation. Release of free ferulic and vanillic acid into the wort at 52°C (with the use of 4.09-14.60 enzyme activity units/L of the mash) and ferulic acid at 62°C (14.60 units/L) was observed. Free p-OH-benzoic and syringic acids were effectively released at 26°C at each enzyme concentration used. Free p-OH-benzoic acid was also released by the enzyme (14.60 U/L) at 52°C-74°C. Free protocatechuic acid was effectively hydrolyzed by the enzyme preparation (8.75 U/L and 14.60 U/L) at 26°C-52°C. Free caffeic acid (effectively released at 26°C-62°C) originated from chlorogenic acid. No p-coumaric acid was released due to the action of bacterial esterase during mashing. Ferulic acid esterase from L. acidophilus K1 exhibited no ability to release free phenolic acids during mashing at 62°C or at 74°C due to its low thermostability. In conclusion, L. acidophilus K1 is an attractive source for the production of ferulic acid esterase, which can be useful for the release of antioxidant phenolic acids in the early stages of mashing. © 2011 The Institute of Brewing & Distilling.

Szwajgier D.,University of Natural science | Wasko A.,University of Natural science | Targonski Z.,University of Natural science | Niedzwiadek M.,University of Natural science | Bancarzewska M.,University of Natural science
Journal of the Institute of Brewing | Year: 2010

In this work, an extracellular ferulic acid esterase was produced in bioreactor cultivations of Lactobacillus acidophilus K1 strain. The enzyme was partially purified using ultrafiltration (10 kDa), dialysis (4-6 kDa) and Fast Protein Liquid Chromatography (Sepharose CM, Sephacryl S-300). A considerable increment of enzyme activity (31-fold) in the final preparation was achieved. Two distinct bands (approx. 21.5 kDa and 39 kDa) were obtained after SDS-PAGE. A high similarity of the purified enzyme (LC-MS/MS analysis) to tannase and ferulic acid esterase from Burkholderia ambifaria MEX-5 was obtained. The optimal pH and temperature for the enzyme activity were 6.3 and 37°C, respectively. The enzyme preparation effectively released phenolic acids (mainly ferulic and p-coumaric acid) from brewer's spent grain. This novel enzyme preparation can be used for the utilisation of a valuable and inexpensive by-product of the brewing industry. © 2010 The Institute of Brewing & Distilling.

In this work, fermentable sugar, total protein, phenolics and ferulic acid content were estimated in sweet worts at different points of lautering. Transfer of these selected malt compounds into worts was analyzed in relation to the method of malt milling (wet milling of malt - the "test worts" or dry milling of malt -the "reference worts"). Glucose, maltose and maltotriose were more rapidly transferred into sweet worts at the early stages of lautering (40 hL and/or 80 hL of wort) after wet milling in comparison to dry milling. Total protein content in the test worts was significantly higher than in the corresponding reference worts at each stage of lautering. Transfer of phenolic compounds and ferulic acid (in the free as well as in the ester form) from the mash into sweet worts was significantly improved by dry milling, but not by wet milling. No difference in the total antioxidant activity was observed between the two types of worts. In conclusion, it can be stated that wet conditioning of malt before milling enhances the fast transfer of fermentable sugars and proteins from the mash into the sweet wort during lautering. Lautering is a time-consuming process, and time reduction without the loss of wort quality should be a priority. Therefore, wet milling can be of interest to professionals in the field as an interesting alternative method to improve the mashing process. © 2011 The Institute of Brewing & Distilling.

Szwajgier D.,University of Natural science | Borowiec K.,University of Natural science
Journal of the Institute of Brewing | Year: 2012

Anticholinesterase activities of mashes produced using wheat ('Wheat Pale') or barley malts ('Pilsner', 'Pale Ale', 'Munich Light', 'Carahell' or 'Carared') were studied by spectrophotometric method. The highest inhibition of acetylcholinesterase and butyrylcholinesterase was observed at 52°C and/or 64°C, followed by a decrease or stabilization of the activity at 72°C. Changes in the total phenolics content in the test mashes were correlated with changes in the acetylcholinesterase and/or butyrylcholinesterase activities. Phenolic acids were singled out from phenolic compounds for more detailed studies owing to their simplicity and structural similarity to well-known cholinesterase inhibitors. The main phenolic acids in the test malts were ferulic, gallic, p-coumaric and vanillic acids followed by chlorogenic, caffeic, syringic, p-OH-benzoic, sinapic and protocatechuic acids. The anticholinesterase activities of the phenolic acids were studied using model standard solutions at concentrations similar to the maximal content of these compounds in the test mashes. Among the phenolic acids, p-coumaric acid had the largest share in the anticholinesterase activity, even though it was present in the test mashes at a significantly lower concentration (~0.38mM L-1) than ferulic acid (~1.00mM L-1). Sinapic acid and p-OH-benzoic acid (0.03 and 0.01mM L-1, respectively) were equally efficient inhibitors as ferulic acid at ~1.00mM L-1. This preliminary study should be extended to other phenolic compounds from malt (wort) in the near future. © 2012 The Institute of Brewing & Distilling.

Szwajgier D.,University of Natural science
Polish Journal of Food and Nutrition Sciences | Year: 2014

In this work, anticholinesterase activities of 24 polyphenolic compounds were tested using the modified Ellman's spectrophotometric method. The most efficient acetyl- and butyrylcholinesterase inhibitors were anthocyanins (pelargonidin, delphinidin and cyanidin), flavones (apigenin and luteolin), flavonols (quercetin, kaempferol and myricetin), as well as dihydrochalcone phloridzin and prenylated chalcone xanthohumol. It was established that all the tested compounds were within a narrow molecular weight range of 254.24-354.40 g/mol, which probably was not discriminative for their inhibitory activity. Among all the classes of polyphenolic compounds, the lowest activities were exerted by flavan-3-ols. The inhibitory activity of the tested polyphenols was decreased by the presence of a 3-hydroxyl group. A simultaneous substitution of a carbonyl group at position 4 and a hydroxyl group at position 3 or a lack of both of these substitutions had no effect on the activity of the investigated compounds. The number and position of other hydroxyl groups in the tested molecules played a minor role in this context. Aglycons were more effective cholinesterase inhibitors than their corresponding glycosylated forms. Overall, the results show that phenolic acids can play a role in neuroprotection. However, further in vitro and in vivo studies involving a larger number of polyphenolic compounds simultaneously with well-known cholinesterase inhibitors should be performed in the nearest future to confirm these findings. © by Institute of Animal Reproduction and Food Research of the Polish Academy of Sciences.

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