Príjem a uvoľňovanie vlhkosti vlnou ožiarenou elektrónovým lúčom

In this work, wool samples a) degreased and stored in desiccator (WD), b) degreased and stored freely (WF), c) cleaned in water and stored freely (WW) were irradiated by accelerated electron beam with doses within the range (0-400) kGy in air. Content of S-sulphonate as primary oxidation product was determined in WD using FTIR spectra inverted in the second-order derivative spectra. The uptake of humidity by all the samples at room temperature and 97% relative humidity was examined gravimetrically. As expected, the highest humidity uptake was observed for WD and the smallest one for WW. Development of the humidity uptake showed some fluctuation for all samples and, for WD the fluctuation corresponded with generated S-sulphonate, presumably due to formation of numerous H-bonds. The increasing uptake of humidity for WD and WW was observed up to 40 kGy dose while for WF, the uptake decreased below the initial level already from 16 kGy. Surface tension was measured using sink-float method combining stalagmometry. The initial surface tension of WW was higher than for WD and WF but, grew equally for all samples from 25 kGy. From 100 kGy dose the surface tension showed stabilized level. The humidity release by WD was measured using thermogravimetry. Variation of the rate humidity release around 100 °C, adequate for desorption of weakly bound water, and the mass residue of the heated wool for 120 °C corresponding to release of total water, showed an inverse dependence. It was concluded that content of S-sulphonate is responsible for variability of the sorption properties. The more S-sulphonate formed, the higher uptake of humidity and the lower rate of humidity release that can be observed. It is suggested that, within a certain range, a properly chosen dose can affect humidity uptake.V tejto práci vzorky vlny a) odmastenej a uloženej v exsikátore (WD), b) odmastenej a uloženej voľne (WF), c) čistenej vo vode a uloženej voľne (WW), boli ožiarené na vzduchu urýchleným elektrónovým lúčom s dávkami v rozsahu (0-400) kGy. Obsah S-sulfonátu ako primárneho oxidačného produktu bol stanovený vo WD pomocou druhej derivácie FTIR. Príjem vlhkosti všetkých vzoriek bol skúmaný gravimetricky pri laboratórnej teplote a relatívnej vlhkosti 97%. Ako sa dalo očakávať, najvyšší príjem vlhkosti bol pozorovaný pre WD, najnižší pre WW. Ukázalo sa, že príjem vlhkosti kolísal vo všetkých vzorkách, pre WD kolísanie korelovalo s vygenerovaným S-sulfonátom, pravdepodobne v dôsledku vzniku početných H-väzieb. Stúpajúci príjem vlhkosti pre WD a WW bol pozorovaný do dávky 40 kGy, zatiaľ čo pre WF príjem klesol pod pôvodnú úroveň už pri dávke 16 kGy. Povrchové napätie bolo merané flotačnou metódou kombinovanou so stalagmometriou. Počiatočné povrchové napätie WW bolo vyššie ako u WD a WF, avšak rástlo rovnako pre všetky vzorky od dávky 25 kGy. Od dávky 100 kGy sa povrchové napätie ustálilo. Uvoľňovanie vlhkosti vo WD bolo merané termogravimetricky. Zmeny rýchlosti uvoľňovania vlhkosti pri teplote okolo 100 °C, adekvátnej desorpcii slabo viazanej vody a hmotnosť zvyšku zahrievanej vlny pri 120 °C zodpovedajúcemu uvoľňovaniu celkovej vody, poskytli inverznú závislosť. Dospeli sme k záveru, že za variabilitu sorpčných vlastností je zodpovedný obsah S-sulfonátu. Čím viac S-sulfonátu sa vytvorilo, tým vyšší nárast vlhkosti a nižšia rýchlosť uvoľňovania vlhkosti bola pozorovaná. Predpokladá sa, že v rámci určitého rozmedzia a pri vhodne zvolenej dávke je možné ovplyvniť príjem vlhkosti

Effect of humic substances and probiotics on growth performance and meat quality of rabbits

The aim of this work was determined effect of supplemental humic substances and probiotics on growth performance and meat quality of rabbits.  The growth performances were observed on two hundred and twelve growing rabbits assigned randomly by weight to two treatments. The treatments included: 1) Control group: in this group were rabbits fed with basal diet during all experiment (35th – 77th day), 2) experimental group: the animals were fed with basal diet+3kg/t humic substances – Humac Nature during whole experiment.  In this group was during fattening period (35th – 49th and 63rd – 70th days of age) added to feed the probiotic preparation – Propoul (Lactobacillus fermentum CCM 7158 1x108 CFU) 2 g per ten pieces. Body weight and feed intake were measured weekly in order to determine the average daily gain, average daily feed intake and gain/feed. The characteristics of meat quality were determined on twelve rabbit males at the age of 77 days, when the rabbits achieved average slaughter weight 2500g. Results of the whole experimental period showed that addition humic substances and probiotic preparation to the diet had positive effect (not significantly) on intensity of growth live weight in the last phase of fattening period. The results of this study suggest that humic substances with probiotics might be utilized as a feed additive in the rabbit diet. It could not significantly improve growth performance and meat quality of rabbits

The Sonic Resonance Method and the Impulse Excitation Technique: A Comparison Study

In this study, resonant frequencies of flexurally vibrating samples were measured using the sonic resonant method (SRM) and the impulse excitation technique (IET) to assess the equivalency of these two methods. Samples were made from different materials and with two shapes (prism with rectangular cross-section and cylinder with circular cross-section). The mean values and standard deviations of the resonant frequencies were compared using the t-test and the F-test. The tests showed an equivalency of both methods in measuring resonant frequency. The differences between the values measured using SRM and IET were not significant. Graphically, the relationship between the resonant frequencies is a line with a slope of 0.9993 ≈ 1

Thermophysical Properties of Kaolin–Zeolite Blends up to 1100 °C

In this study, the thermophysical properties such as the thermal expansion, thermal diffusivity and conductivity, and specific heat capacity of ceramic samples made from kaolin and natural zeolite are investigated up to 1100 °C. The samples were prepared from Sedlec kaolin (Czech Republic) and natural zeolite (Nižný Hrabovec, Slovakia). Kaolin was partially replaced with a natural zeolite in the amounts of 10, 20, 30, 40, and 50 mass%. The measurements were performed on cylindrical samples using thermogravimetric analysis, a horizontal pushrod dilatometer, and laser flash apparatus. The results show that zeolite in the samples decreases the values of all studied properties (except thermal expansion), which is positive for bulk density, porosity, thermal diffusivity, and conductivity. It has a negative effect for thermal expansion because shrinkage increases with the zeolite content. Therefore, the optimal amount of zeolite in the sample (according to the studied properties) is 30 mass%