Endokrini i metabolički profil junica holštajna i crvenog holštajna u peripartalnom periodu

The aim of this stady was to examine the relationship between triiodothyronine (T3), thyroxin (T4), insulin-like growth factor-I (IGF-I) and blood serum liver function biomarkers concentrations in Holstein and Red Holstein heifers during the peripartal period. In the first experimental group (I) were heifers of Holstein Friesian breed (n=10), and in the second experimental group (II) were Red Holstein heifers (n=10). Blood samples were taken from the vena coccygea three times during the short peripartal period (5 days before delivery, at delivery and 5 days after delivery), and blood serum samples were separated after spontaneous coagulation. Blood serum T3, T4 and IGF-I concentrations were determinated using radioimmunoassay (RIA). Blood serum concentrations of glucose (G), total protein (TP), albumin, (Alb), urea, total bilirubin (tBil) and aspartate aminotrasferase (AST) were determined using commercial ELISA kits. The statistical significance between means was determined using Student t-test. Blood serum T3 concentration in Group II was significantly lower after delivery, and T4 concentration was significantly higher before delivery (p lt 0.05), compared to Group I. Mean blood serum IGF-I concentrations between the two experimental groups were not significantly different at all time intervals. Relationships between the determined hormones showed a median positive correlation between T3, and T4 (r=0.74) in Group I and highly positive correlation in Group II (r=0.81). Blood serum thyroid gland hormones and IGF-I concentrations in healthy heifers during peripartal period vary considerably, the lowest values being determined immediately after calving in both experimental groups. Blood serum G, TP, Alb and urea concentrations were significantly higher in Group I at all investigated time intervals. Blood serum tBil concentration was significantly higher after partus in Group I (11.02 ± 3.33 : 8.49 ± 3.35 μmol/L, Group I vs. II, respectively), and AST activity was not significantly different at all intervals.Cilj ovih istraživanja je bio određivanje koncentracije triijodtironina (T3), tiroksina (T4), insulinu sličnog faktora rasta-I (IGF-I) i biomarkera, pokazatelja funkcionalnog stanja jetre u krvnom serumu dva varijeteta junica Holštajn rase u peripartalnom periodu. Prvu eksperimentalnu grupu (I) činile su junice crno belog holštajna (n=10), a drugu grupu (II) junice crvenog holštajna (n=10). Krv za analize je uzimana iz repne vene, tri puta u peripartalnom periodu (5 dana pre partusa, na dan partusa i do 5 dana posle partusa), a krvni serum je odvajan nakon spontane koagulacije. U krvnom serumu je radioimunološkom metodom (RIA, INEPZemun) određivanja koncentracija trijodtironina (T3), tiroksina (T4) i insulinu sličnog faktora rasta-I (IGF-I). Koncentracija glukoze (G), ukupnih proteina (TP), albumina, (Alb), ureje, ukupnog bilirubina (tBil) i aktivnost aspartat aminotrasferaze (AST) je određivana upotrebom komercijalnih ELISA kitova. Statistička značajnost razlika srednjih vrednosti ispitivanih endokrinih i metaboličkih parametara je određena Studentovim t-testom. Dobijeni rezultati ukazuju na vrlo različite koncentracije hormona štitne žlezde u krvnom serumu junica oba varijeteta holštajna pre i posle partusa. Koncentracija T3 je bila statistički značajno niža u grupi II nakon partusa, a T4 značajno viša pre partusa (p lt 0.05) u odnosu na nivo hormona u grupi I. Za prosečne vrednosti koncentracija IGF-I, između isptivanih grupa nije ustanovljena statistički značajna razlike ni u jednom od tri perioda ispitivanja. Utvrđena je srednje pozitivna korelacija između koncentracije T3 i T4 (r=0,74) u krvnom serumu junica grupe I, i vrlo visoka pozitivna korelacija u grupi II (r=0,81). Koncentracija TP, Alb i ureje bila je statistički značajno viša kod junica grupe I u sva tri perioda ispitivanja. Nivo tBil u krvnom serumu je takođe bio povišen kod junica grupe I u sva tri perioda ispitivanja, ali su statistički značajne razlike između srednjih vrednosti ustanovljene samo u periodu nakon partusa. Aktivnost AST u krvnom serumu junica oba varijeteta značajno je varirala u svim periodima ispitivanja i nisu ustanovljene statistički značajne razlike između srednjih vrednosti

Experimental investigation of heat transport in homogeneous bubbly flow

In this work we study the heat transport in inhomogeneous bubbly flow. The experiments were performed in a rectangular bubble column heated from one side wall and cooled from the other, with millimetric bubbles introduced through one half of the injection section (close to the hot wall or close to the cold wall). We characterise the global heat transport while varying two parameters: the gas volume fraction , and the Rayleigh number . As captured by imaging and characterised using Laser Doppler Anemometry (LDA), different flow regimes occur with increasing gas flow rates. In the generated inhomogeneous bubbly flow there are three main contributions to the mixing: (i) transport by the buoyancy driven recirculation, (ii) bubble induced turbulence (BIT) and (iii) shear-induced turbulence (SIT). The strength of these contributions and their interplay depends on the gas volume fraction which is reflected in the measured heat transport enhancement. We compare our results with the findings for heat transport in homogeneous bubbly flow from Gvozdić et al. (2018). We find that for the lower gas volume fractions (), inhomogeneous bubbly injection results in better heat transport due to induced large-scale circulation. In contrast, for , when the contribution of SIT becomes stronger, but so does the competition between all three contributions, the homogeneous injection is more efficient

Twente mass and heat transfer water tunnel: Temperature controlled turbulent multiphase channel flow with heat and mass transfer

A new vertical water tunnel with global temperature control and the possibility for bubble and local heat and mass injection has been designed and constructed. The new facility offers the possibility to accurately study heat and mass transfer in turbulent multiphase flow (gas volume fraction up to 8%) with a Reynolds-number range from 1.5 × 104 to 3 × 105 in the case of water at room temperature. The tunnel is made of high-grade stainless steel permitting the use of salt solutions in excess of 15% mass fraction. The tunnel has a volume of 300 l. The tunnel has three interchangeable measurement sections of 1 m height but with different cross sections (0.3 × 0.04 m2, 0.3 × 0.06 m2, and 0.3 × 0.08 m2). The glass vertical measurement sections allow for optical access to the flow, enabling techniques such as laser Doppler anemometry, particle image velocimetry, particle tracking velocimetry, and laser-induced fluorescent imaging. Local sensors can be introduced from the top and can be traversed using a built-in traverse system, allowing, for example, local temperature, hot-wire, or local phase measurements. Combined with simultaneous velocity measurements, the local heat flux in single phase and two phase turbulent flows can thus be studied quantitatively and precisel