Spruce chips stabilization in wood-cement materials: Effect of matrix composition

The paper presents research focused on the behaviour of wood-cement composites with a modified matrix. This matrix has an impact on the stabilization of the spruce wood content. Silicate matrix based on Portland and blended cement was modified by finely ground thermal power plant slag (TPPS) and limestone (LS). Four types of wood-cement composite were subjected to water immersion tests for 28 days. During water immersion, both swelling in thickness and mass changes were analysed. The amount of sugars and pH in leachate were determined after 7 day intervals. Mechanical properties and microstructures were analysed before and after water immersion. Different behaviour with regard to spruce chips stabilization was proved in dependence of wood-cement matrix modification. Differences in thickness, swelling and sugar leach indirectly indicate the influence of the wood-cement composites matrix composition on the stabilization of spruce chips contained in this matrix. Boards with the matrix modified with thermal power plant slag showed the highest thickness swelling (%) and sugar leaching (0,042 %). Therefore, in the presence of thermal power plant slag modified matrix, spruce chips are more susceptible to sugar leach. The results of strength characteristics confirmed that sugars leached during hydration and after longer contact of wood-cement composites with water have no negative influence in their final properties in the case of all materials tested (reference and modified). &nbsp

Karyological and morphological variations within the genus Dysphania (Chenopodiaceae) in Bulgaria

The karyological and morphological variability of species from the genus Dysphania were studied. The results demonstrated that genus Dysphania is represented in Bulgaria by five species: Dysphania ambrosioides, D. multifida, D. botrys, D. schraderiana and D. pumilio. The first two species are tetraploids with chromosome number 2n = 32 for D. ambrosioides and 2n = 36 for D. multifida. The remaining three species are diploids with 2n = 18. The results from statistical analysis demonstrated that the main source of phenotype variation in the species is the interpopulation variation. The specific characters which allowed their recognition are themorphological characteristics of the perianth lobes, the upper leaves and the seeds. The distinction between D. multifida, D. ambrosioides and D. schraderiana is based on differences in the quantitative traits, while in D. botrys and D. pumilio qualitative traits are also important. The basic evolutionary mechanisms are polyploidy and diploidy.Atendency towards reduction in the size of generative organs and the number of perianth lobes was found

Effect of Physical Treatment on the Properties of Composites Based on Natural Fibres

Due to the low density and high porosity of the hemp hurds, the combination of hemp and binder creates a building material with good thermal and acoustic insulation properties. Today hemp hurds can be used in high-quality products such as hemp concrete, fibre board and composites.In this paper, the attention is given to the study of the properties of lightweight composites based on modified hemp hurds as filler and MgO-cement as binder. The cohesion of the filler and of the binder is an important factor in the development of mechanical properties. The impact of ultrasonic treatment of hemp hurds and its cooking in water for 1h on the physical and mechanical properties (compressive strength, density, water absorbability, thermal conductivity) of the composites hardened in indoor condition was studied. The observation is also focused on the influence of the hemp hurds length. The durability of produced composites was studied under different conditions

Vitamin E: Recommended Intake

Data of vitamin E intake and status are controversial. Vitamin E is an essential micronutrient for humans and achieving an optimal status is assumed to produce beneficial health outcomes. Dietary intake recommendations for vitamin E vary considerably by different countries and organizations. It appears to be still a challenge to define these despite the wealth of data published. Vitamin E requirements have been proposed to depend on other nutritional factors, such as the intake of polyunsaturated fatty acids (PUFA). Although several foods contain naturally occurring sources of vitamin E, it is frequently the case that the intake recommendations are not achieved. Several other dietary factors affect the need for vitamin E. In this regard, significant challenges to be considered include the efficiency of other tocopherol variants and their properties that could affect the revision of the nutritional recommendations for vitamin E. Particularly, an ever-increasing evidence indicates that other vitamin E homologs may potentially present with a higher biological activity. Low dietary consumption of vitamin E, coupled with compelling evidence that increased intake of vitamin E above current recommendations for the general population may benefit older individuals

Molecular characteristics of mismatch repair genes in sporadic colorectal tumors in Czech patients

BACKGROUND: Mismatch repair (MMR) genes are known to be frequently altered in colorectal cancer (CRC). Both genetics and epigenetics modifications seems to be relevant in this phenomenon, however it is still not clear how these two aspects are interconnected. The present study aimed at characterizing of epigenetic and gene expression profiles of MMR genes in sporadic CRC patients from the Czech Republic, a country with one of the highest incidences of this cancer all over Europe. METHODS: Expression levels and CpG promoter methylation status of all MMR genes were evaluated in DNA from tumor and adjacent mucosal samples of 53 incident CRC patients. RESULTS: We have found significantly increased transcription levels in EXO1 gene in tumor tissues (P = 0.05) and significant over-expression of MSH3 gene in colon tumors when compared to adjacent mucosal tissues (P = 0.02). Interestingly, almost all MMR genes were differently expressed when localization of tumors was compared. In particular, colon tumors showed an up-regulation of EXO1, MSH2, MSH3, MSH6, and PMS2 genes in comparison to rectal tumors (P = 0.02). Expression levels of all MMR genes positively correlated between each other. The promoter methylation of MLH1 gene was observed in 9% of CRC tissues only. CONCLUSIONS: In our study, we have observed different pattern of MMR genes expression according to tumor localization. However, a lack of association between methylation in MMR genes and their corresponding expressions was noticed in this study, the relationship between these two aspects is worthy to be analyzed in larger population studies and in pre-malignant stages

Wpływ alternatywnego spoiwa na właściwości kompozytu z włóknami konopnymi

Composites based on natural fibres as organic filler are studied for several years because traditional building materials such as concrete are increasingly being replaced by advanced composite materials (fibre reinforced cement). The current trend in the construction industry is the effort to achieve sustainable development using rapidly renewable material resources instead of limited raw materials as well as using alternative materials. The need for development of promising and environmentally friendly materials is related to the industrial interest in the use of natural plant fibres as reinforcement into lightweight composites. The attention is given to hemp fibres as a substitute for synthetic fibers in lightweight composites due to their unique mechanical, thermal insulation, acoustic and antiseptic properties. Optimizing the adhesion of hemp plant fibre to the inorganic matrix in the composite is related to the modification of hemp fibers and/or the appropriate option and treatment of binder. In this paper, the attention is given to the study properties of composite based on hemp hurds as filler and alternative binder (MgO-cement). The hemp as a building composite component is rapidly renewable, carbon-negative, non-toxic, mildew-resistant and pest-free. Cement based on MgO seems to be a suitable binding agent for composites based on hemp hurds. Experimental work is focused on the study of impact of alternative binder on the selected properties of prepared lightweight composites and variation of mixtures based on hemp hurds and alternative binder focused on the MgO and SiO2 component (silica sand and silica fume in variation). The evaluation of the physical and mechanical properties of hemp hurds composites with alternative binder is given. The results have shown that by incorporating hemp hurds into a magnesium oxide cement matrix it is possible to prepare materials with suitable thermal insulating properties usable in non-load-bearing structures.Od kilku lat badane są kompozyty na bazie włókien naturalnych jako wypełniacze organiczne, ponieważ tradycyjne materiały budowlane, takie jak beton, są coraz częściej zastępowane zaawansowanymi materiałami kompozytowymi (cement wzmacniany włóknami). Obecną tendencją w branży budowlanej jest dążenie do osiągnięcia zrównoważonego rozwoju przy wykorzystaniu szybko odnawialnych surowców, a nieograniczonych surowców, a także przy użyciu alternatywnych materiałów. Potrzeba opracowania ekologicznych dla środowiska materiałów jest związana z przemysłowym wykorzystaniem naturalnych włókien roślinnych jako zbrojenia do lekkich materiałów kompozytowych oraz włókien konopnych jako substytut włókien syntetycznych w lekkich kompozytach ze względu na ich unikalne własności mechaniczne, termoizolacyjne, akustyczne i antyseptyczne. Optymalizacja przyczepności włókna roślinnego konopi do matrycy nieorganicznej w kompozycie jest związana z modyfikacją włókna konopnego i/lub odpowiednią opcją i obróbką spoiwa. W niniejszym dokumencie zwrócono uwagę na właściwości badawcze kompozytu bazującego na opasach konopnych (w odcieniach drewna konopi) jako wypełniacza i alternatywnego środka wiążącego (MgO-cement). Konopie jako komponent złożony z budynków są szybko odnawialne, są odporne na węgiel, nietoksyczne, odporne na pleśń i wolne od szkodników. Wydaje się, że cement na bazie MgO jest odpowiednim środkiem wiążącym dla kompozytów na bazie konopi. Eksperymentalne prace koncentrują się na badaniu termicznego przetwarzania naturalnego surowego materiału magnezytowego do jego późniejszego wykorzystania jako alternatywnego składnika wiążącego do lekkich materiałów kompozytowych oraz zróżnicowania mieszanek kompozytowych opartych na opaskach konopnych i alternatywnym środku wiążącym skupionym na składniku MgO i SiO2. Ocenę fizycznych i mechanicznych właściwości konopnych prasuje kompozyty z alternatywnym spoiwem. Wyniki wykazały, że poprzez włączenie konopnych włókien do matrycy cementowej tlenku magnezu można przygotować materiały o odpowiednich właściwościach termoizolacyjnych użytych w konstrukcjach nie obciążających

Thermal Stress Effect on Density Changes of Hemp Hurds Composites

The aim of this article is to study the behavior of prepared biocomposites based on hemp hurds as a filling agent in composite system. In addition to the filler and water, an alternative binder, called MgO-cement was used. For this objective were prepared three types of samples; samples based on untreated hemp hurds as a referential material and samples based on chemically (with NaOH solution) and physically (by ultrasonic procedure) treated hemp hurds. The thermal stress effect on bulk density changes of hemp hurds composites was monitored. Gradual increase in temperature led to composites density reduction of 30-40 %. This process is connected with mass loss of the adsorbed moisture and physically bound water and also with degradation of organic compounds present in hemp hurds aggregates such as pectin, hemicelluloses and cellulose. Therefore the changes in the chemical composition of treated hemp hurds in comparison to original sample and its thermal decomposition were also studied

A Closer Look at the Halloween Effect: The Case of the Dow Jones Industrial Average

The Halloween effect is one of the most famous calendar anomalies. It is based on the observation that stock returns tend to perform much better over the winter half of the year (November–April) than over the summer half of the year (May–October). The vast majority of studies that investigated the Halloween effect over the recent decades focused only on stock indices. This means that they evaluated whether a stock index follows the Halloween effect pattern, but they omitted digging a little deeper and analyze the Halloween effect on the individual stocks level. This paper investigates to what extent the blue-chips stocks included in the Dow Jones Industrial Average are affected by the Halloween effect and whether the Halloween effect is widespread or the behavior of the whole index is driven by only a handful of stocks that are strongly affected by the Halloween effect. The results show that, although the strength of the Halloween effect varies quite rapidly from stock to stock, the vast majority of analyzed stocks experienced a notably higher average winter period than summer period returns over the 1980–2017 period. Moreover, in 18 out of 35 cases, the Halloween effect was statistically significant