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A Comparison of Preconditioning Methods for Saddle Point Problems with an Application to Porous Media Flow Problems
Axelsson, Owe ; Blaheta, Radim ; Hasal, Martin
The paper overviews and compares some block preconditioners for the solution of saddle point systems, especially systems arising from the Brinkman model of porous media flow. The considered preconditioners involve different Schur complements as inverse free Schur complement in HSS (Hermitian - Skew Hermitian Splitting preconditioner), Schur complement to the velocity matrix and finally Schur complement to a regularization block in the augmented matrix preconditioner. The inverses appearing in most of the considered Schur complements are approximated by simple sparse approximation techniques as element-by-element and Frobenius norm minimization approaches. A special interest is devoted to problems involving various Darcy, Stokes and Brinkman flow regions, the efficiency of preconditioners in this case is demonstrated by some numerical experiments.
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STRAIN ENGINEERING OF THE ELECTRONIC STRUCTURE OF 2D MATERIALS
del Corro, Elena ; Peňa-Alvarez, M. ; Morales-García, A. ; Bouša, Milan ; Řáhová, Jaroslava ; Kavan, Ladislav ; Kalbáč, Martin ; Frank, Otakar
The research on graphene has attracted much attention since its first successful preparation in 2004. It possesses many unique properties, such as an extreme stiffness and strength, high electron mobility, ballistic transport even at room temperature, superior thermal conductivity and many others. The affection for graphene was followed swiftly by a keen interest in other two dimensional materials like transition metal dichalcogenides. As has been predicted and in part proven experimentally, the electronic properties of these materials can be modified by various means. The most common ones include covalent or non-covalent chemistry, electrochemical, gate or atomic doping, or quantum confinement. None of these methods has proven universal enough in terms of the devices' characteristics or scalability. However, another approach is known mechanical strain/stress, but experiments in that direction are scarce, in spite of their high promises.\nThe primary challenge consists in the understanding of the mechanical properties of 2D materials and in the ability to quantify the lattice deformation. Several techniques can be then used to apply strain to the specimens and thus to induce changes in their electronic structure. We will review their basic concepts and some of the examples so far documented experimentally and/or theoretically.
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ELECTRON BEAM REMELTING OF PLASMA SPRAYED ALUMINA COATINGS
Matějíček, Jiří ; Veverka, J. ; Čížek, J. ; Kouřil, J.
Plasma sprayed alumina coatings find numerous applications in various fields, where they enhance the properties of the base material. Examples include thermal barriers, wear resistance, electrical insulation, and diffusion and corrosion barriers. A typical structure of plasma sprayed coatings, containing a multitude of voids and imperfectly bonded interfaces, gives them unique properties - particularly low thermal conductivity, high strain tolerance, etc. However, for certain applications such as permeation barriers or wear resistance, these voids may be detrimental.\nThis paper reports on the first experiments with remelting of plasma sprayed alumina coatings by electron beam technology, with the purpose of densifying the coatings and thereby eliminating the voids. Throughout the study, several parameters of the e-beam device were varied - beam current, traverse velocity and number of passes. The treated coatings were observed by light and electron microscopy and the thickness, structure and surface morphology of the remelted layer were determined and correlated with the process parameters. Based on the first series of experiments, the e-beam settings leading to dense and smooth remelted layer of sufficient thickness were obtained. In this layer, a change of phase composition and a marked increase in hardness were observed.\n
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Sorption and Stabilization of Metals/Mettalloids by Innovative Synthesized Sorbent Amochar.
Ouředníček, P. ; Trakal, L. ; Komárek, M. ; Pohořelý, Michael
Remediation of contaminated soil which is based on stabilization and immobilization of potential\nhazardous substance by sorption materials has been studied intensively nowadays. Biochar – activated organic carbon belongs to this group of stabilizing agents which can adsorb wide range of contaminants, including metals/metalloids. Surface area of the biochars is quite large in general and functional groups (e.g. COO–) can form chelates or alkaline elements on the surface, which is represented by cation exchange capacity. Altogether with the high pH values (7.00 – 10.00), biochars are quite effective sorbents and can adsorb metals/metalloids from the solution (ground water), especially in acidic soils (in the environments affected by intensive mining activities). Sorption\neffectiveness can be increased (especially for As (V) or Cr (VI) sorption) by modification of biochar by various types of secondary oxides. Innovative sorbent AMOchar (AMO + biochar) has been synthesized currently. The product was prepared by adding of biochar to the reaction solution during amorphous manganese oxide (AMO) synthesis. The AMOchar was formed mainly by Mn-oxalates which had coated surface of the pristine biochar. AMOchar composite was able to remove significantly higher amounts of various metal(loid)s from the solution despite the rather high pH of the material. Sorption effectiveness was high not only in case of Pb (II) sorption (almost 99%), and Cd(II) (51.2%), but also a very high amount of As(V), 91.4%. Additionally, both AMOchar composite was able to reduce Mn leaching. This can avoid potential post-contamination caused by the dissolution of less stable Mn-oxalates as observed in the pure AMO.
Fulltext: content.csg -  PDF
Plný tet: SKMBT_22316111113040 - PDF
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Determination of content substances for selected species and varieties of roses.
Slavíková, Eva ; Sus, Josef (advisor) ; Súkeníková, Tereza (referee)
This bachelor's work is focused on comparing the most significant content substance, vitamin C, in fruits of chosen rose kinds species and varieties. Herbal products are often seen by people as products of "second choice", when failure of allopathic treatment occurs, which is focused especially on suppressing symptoms of illness, but it ignores health of the human body as whole. That's why are herbal products often alternative for therapy of chronic diseases. The base of this work is extensive literary research and results of laboratory measurings. Literary part of this work includes description of botanical classification of rose plants. There is stated basic characteristic of individual rose species and their morphological features. In following chapters is composed overview of effective substances in rose fruits and their effect on human health. In practical part of this work are included results of laboratory tests for determining ascorbic acid content for chosen samples of rose species and it also includes results of weighing and measuring of fruit samples of chosen rose species. There are also stated chosen rose species and shortly their origin and description, in the beginning of practical part. For practical part were chosen samples of species. Results of practical part are compiled into statistic tables and graphs and it confirms high content of ascorbic acid in rose fruits. This content is in range of cca 300 - 900 mg.100 g-1. Due to growing interest in alternative treatment options and "clean" natural product, it can be assumed, that many plants of Rosaceae family will keep its place in treatment practice. Those plants will be used not only for treatment of acute and chronic diseases, but also for cosmetic products production, thanks to its large effects and process options.
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Arctic tundra dendrochronology
Lehejček, Jiří ; Svoboda, Miroslav (advisor) ; Monika, Monika (referee)
Historically unprecedented environmental change in the Arctic ecosystems is often given into the context of its past and possible future development. In the region where instrumental meteorological observations are scarce archives need to be investigated in order to address this issues. The comprehensive synthesis one of the archives: long-live circumpolar evergreen Juniperus communis L. shrub is presented here. 20 individuals from southwest Greenland were investigated at the cell anatomy level to understand the ecology of the species and unhide its potential for environmental and climate reconstructions. The findings are as follows:
i) Stop of exponential cross-sectional conduit-lumen widening with increasing age is in contrast with conduit-lumen nature of trees. This indicates that shrubs do not need to saturate their water and nutrient demands via traits of classical hydraulic conductivity law but rather developed different mechanisms. Extreme weather conditions result in prostrate growth form. However, different weather factors probably influence shrub growth differently: While snow and wind act mechanically (a), temperature influences the form of growth physiologically (b). a) So long as the young shrub stem has high resilience to bend back to an upright position after snow melt and so long as it can withstand the wind during the vegetation season it most likely grows upright and the conduit-lumens widen. b) Temperature, resp. freeze-thaw events are responsible for the shrubs preference of safety (finite size of conduit-lumens) over hydraulic efficiency, thus not allowing for more primary growth. All of these (and other) factors are apparently working together and the transition of vertical to more horizontal growth is gradual. As a consequence, the conduit-lumen sizes may not have to be further increased (due to ecophysiological restrictions possibly also must not) because water is no longer transported against gravity.
ii) Observed age/growth trend has to be taken into consideration for further employment of the wood anatomical parameter in paleoenvironmental studies. That is, shrub cell parameters can only be used for this purposes if correctly detrended. This allows for more accurate as well as longer reconstructions because youth trend was often neglected in reconstructions based on shrub annual-rings.
iii) The south-western Greenland Ice-Sheet (GrIS) melt rates reconstruction is presented for the whole 20th century. This part of GrIS is considered as the most active. According to the presented reconstruction current GrIS melt rates are not uncommon for the last century being comparable to first decades of 20th century. This finding is particularly important contribution to the debate on Atlantic meridional overturning circulation (AMOC). Too high fresh water inputs into the Northern Atlantic from GrIS melting may slow down or even stop the AMOC which would result in more continental climate in Europe. Presented results indicate that this threshold lies higher than observed current melt rates of GrIS.
Fascinating Juniperus comunnis species has shown to be able to address many ecological as well as environmental open questions and due to its longevity and abundant distribution has a great potential to become an important player in the Arctic research.
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Nutritional analysis and optimization of breeding of selected species of edible insects under conditions of the Czech Republic with regard to human health
Adámková, Anna ; Kouřimská, Lenka (advisor)
All over the world, the edible insects are considered a highly nutritious food with high protein and fat content. However, the nutritional value of insect is not constant. It can be affected by species, developmental stage, rearing technology or nutrition.
Therefore, this thesis was aimed at obtaining the selected nutritional value of edible insects. Analyses were focused on the determination of the crude protein content, fat content, fatty acid profile and sterols in selected species of edible insects, which can be commonly reared in the Czech Republic. At the same time we also analysed samples of insects reared on the island of Sumatra to evaluate the influence of the climate on the nutritional value. The main aim of the thesis was the determination of optimal breeding conditions, developmental stages and feed rations for obtaining good production of insects with nutritional properties suitable for human nutrition. The analyses showed a high nutritional value of selected insect species, but also confirmed the significant differences in the content of individual nutrients between different species depending on the climate conditions and developmental stage. Comparing the fat and crude protein content in edible insects and other conventional sources of meat it has been found, that the examined insect is similar to beef concerning the fat and crude protein content. The results obtained are the basis for determining the appropriate rearing conditions and developmental stages for obtaining insect with the desired nutritional properties for human nutrition.
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Population genetic analysis of Old Kladruber horse
Vostrá Vydrová, Hana ; Majzlík, Ivan (advisor) ; Karel, Karel (referee)
The Old Kladruber horse, along with the Lipizzaner horse, Andalusian horse and Lusitano horse, is of the original Italo-Spanish type. The Old Kladruber horse is kept in two colour varieties (grey and black). Because the population is closed, there is a concern about the loss of genetic variation. The genetic diversity and population structure were analysed in the Old Kladruber horse breed based on the pedigree information of animals that were registered in the Studbook to identify factors that may have affected the genetic variability of the breed. Pedigree records collected from 1729 to 2013 contained information on 7971 animals that were used in the analyses. The pedigree depth was up to 33 generations, with an average of 15.1 complete generations. The effective number of founders and ancestors contributing to the current genetic pool was 92.69 and 17.16, respectively. The average values of the inbreeding coefficient were as follows: 13% (with a maximum value of 29%) for the reference population (individuals that can currently take part in reproduction, n=612), 11% for the grey variety (with a maximum value of 25%) and 15% for the black variety (with a maximum value of 29%). The proportion of inbred animals was high (99%). The average rate of inbreeding in the reference population was 1%: 0.8% for the grey variety and 1.1% for the black variety, and the respective estimates of the effective population sizes were 52 for the reference population, 62 for the grey variety and 45 for the black variety. The estimated percentage of genetic diversity lost due to non-random mating within subpopulations and the reference population was 1.0, 1.0 and 1.2%, respectively. The total loss of genetic diversity in the reference population, in the grey variety and in the black variety was 11%, 13% and 17%, respectively.
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Antioxidant, anti-proliferative and immunomodulatory effect of fruits, vegetables and mushrooms in vitro
Doskočil, Ivo ; Havlík, Jaroslav (advisor) ; Orsák, Matyáš (referee)
Recently there has been an increasing interest in discovering of new species of plants and mushrooms which have antioxidant or anti proliferative activity. The interest is caused by the fact that these species have medicinal and food utilization. These properties of plants and mushrooms can be used when dealing with many diseases which may be connected with oxidative stress (inflammatory bowel disease, cardiovascular disease, hypertension, and tumour disease, etc.).
The thesis propounds characteristics of in vitro antioxidant and anti proliferative activity of 19 types of juices and 28 methanol extracts of fruits and vegetables, which are common parts of a diet. In the thesis there are also characteristics of 13 ethanol extracts of edible mushrooms of the order of Polypore (Popyporales). Antioxidant activity was quantifie by 2, 2 diphenyl 1 picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), and inhibition of nitric oxide (NO) production. Cytotoxicity was measured by MTT (3 (4,5 dimethylthiazol 2 yl) 2,5 diphenyltetrazolium bromide. Immunomodulatory activity was determined by an assay of phagocytic activity of human neutrophil granulocytes. Further a total phenolic content (TPC) and total beta glucan content were investigated; these are considered to be the potentially active constituents participating in mentioned activities.
From the obtained results it is evident that juices (TPC = 1603.2 mg GAE/L; ORAC = 438.5 umol TE/g)
and a bilberry (Vaccinium myrtillus) fruit extract (ORAC 836.6 umol TE/g; DPPH = 404.6 umol TE/g) showed
the highest antioxidant activity of all tested samples of fruits and vegetables. Capsicum (Capsicum L.)
juices (TPC = 642.1 mg GAE/L; ORAC = 127.9 umol TE/g) and a radish (Raphanus sativus L.) extract
(ORAC 724.5 umol TE/g; DPPH = 52.2 umol TE/g) also proved to have the high values of antioxidant activity. From the tested fruits and vegetables the following inhibited to produce a nitric oxide: onion (Allium cepa L) juices (lowered the NO production by 57%), tangerine juices (Citrus reticulata Blanco)(by 52%), broccoli (Brassica oleracea var. botrytis italic) extract (by 21%), and orange (Citrus sinensis Pers.) extract (by 10%). Concerning edible
mushrooms, Lentinus tigrinus (Bull.) Fr. (TPC = 216.2 umol GAE/g of extract), Ganoderma lucidum (Curtis) P. Kras (TPC = 257.9 umol GAE/g of extract), and Royoporus badius (Pers.) A.B. De (TPC = 257.8 umol GAE/g of extract) presented the highest phenolic content. Sparassis crispa (Wulfen) Fr. (117.4 mg/g of extract) had the highest content of beta glucan. Substantial effect on phagocytic activity of granulocytes was noticed in connection with Neolentinus lepideus (Fr.) Redhead & Ginns, Polyporus squamosus (Huds.) Fr., and S. crispa. In connection with the latter of mentioned mushrooms, a moderate inhibitory effect towards HT 29 human colorectal adenocarcinoma cell line
(IC50 = 107 ug/ml of extract) was noticed.
The results indicate that the tested plants and mushrooms can be beneficial when reducing the negative effects of oxidative stress. The oxidative stress has been recognized as a contributing factor to a whole range of diseases and the reduction of the oxidative stress may lead to the decrease in the possibility of the diseases´ progression. The results show the possible favourable effects on the human health. When evaluating the results, the following fact should be taken into consideration; the in vitro tests and screenings are considered to be the first phase of systematic research of the effects and serve for the choice of respondents for further detailed studies.
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