Enhanced visualisation of complex thermofluid data: Vertical and horizontal combined convection and microscale heat transfer cases

Copyright @ 2000 UITIn general, convective heat transfer is an 'n-dimensional' problem where n is well in excess of 3 for steady flows. Traditionally, the method of dimensional analysis results in a small number of dimensionless groups. In the case of steady forced convection these can reduce to three, namely the Nusselt (Nu), Reynolds (Re) and Prandtl (Pr) numbers, for heat transfer, fluid flow regime and fluid properties respectively. Again, traditionally, data are presented on log-log graphs, say of Nu versus Re, with Pr being a possible third parameter. For natural convection, the Grashof number (Gr) expresses buoyancy effects in place of Re, while for combined (natural and forced) convection Gr becomes additional to, rather than replacing, Re. Using sets of data for: (a) vertical combined convection in nuclear safety, (b) horizontal combined convection review material, and (c) microchannel heat transfer, in the first part of this paper we survey this problem. We reach the following conclusions: that heat transfer data are presented in either 'holistic' or 'reductive' modes, and that other thermodynamic performance data are related to the generic scientific cases of (a) 3-dimensional space and (b) multi-dimensional space. In the second part of the paper we present a first attempt at applying design-type procedures to specifying this problem. Visualisation priorities are suggested from which particular solutions will be developed in future

Inhibition of food intake in obese subjects by peptide YY3-36

Background: The gut hormone fragment peptide YY3-36 (PYY) reduces appetite and food intake when infused into subjects of normal weight. In common with the adipocyte hormone leptin, PYY reduces food intake by modulating appetite circuits in the hypothalamus. However, in obesity there is a marked resistance to the action of leptin, which greatly limits its therapeutic effectiveness. We investigated whether obese subjects were also resistant to the anorectic effects of PYY.Methods: We compared the effects of PYY infusion on appetite and food intake in 12 obese and 12 lean subjects in a double-blind, placebo-controlled, crossover study. The plasma levels of PYY, ghrelin, leptin, and insulin were also determined.Results: Caloric intake during a buffet lunch offered two hours after the infusion of PYY was decreased by 30 percent in the obese subjects (P<0.001) and 31 percent in the lean subjects (P<0.001). PYY infusion also caused a significant decrease in the cumulative 24-hour caloric intake in both obese and lean subjects. PYY infusion reduced plasma levels of the appetite-stimulatory hormone ghrelin. Endogenous fasting and postprandial levels of PYY were significantly lower in obese subjects (the mean [+/-SE] fasting PYY levels were 10.2+/-0.7 pmol per liter in the obese group and 16.9+/-0.8 pmol per liter in the lean group, P<0.001). Furthermore, the fasting PYY levels correlated negatively with the body-mass index (r=-0.84, P<0.001).Conclusions: We found that obese subjects were not resistant to the anorectic effects of PYY. Endogenous PYY levels were low in the obese subjects, suggesting that PYY deficiency may contribute to the pathogenesis of obesity

Effect of antenna element properties and array orientation on performance of MIMO systems

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Evaluation of Hypoglycaemic Efficacy of Aqueous Seed Extract of Aframomum melegueta in Alloxan-induced Diabetic Rats

The hypoglycaemic efficacy of aqueous seed extract of Aframomum melegueta was investigated in alloxaninduced diabetic rats. Twenty five albino rats (Rattus novergicus, average weight: 150g) were randomly divided into five groups of five (5) rats each. For the diabetic group, diabetes mellitus was induced by intraperitoneal injection of 5% solution of alloxan at a dose of 150 mg/kg body weight. Diabetes was confirmed 72 hours after alloxan injection if fasting blood glucose (FBG) was . 10 mmol/l. Two control groups: non-diabetic (positive) and diabetic (negative) were administered tap water as vehicle solvent, throughout the duration of the experiment. The remaining three groups received 100 mg/kg of metformin, 200 and 400 mg/kg orally and aqueous seed extract of Aframomum melegueta respectively and simultaneously. Fasting blood glucose was evaluated daily. The results showed that oral administration of aqueous extract of A. melegueta to diabetic rats lowered blood glucose to normal level within 6 days of administration, while metformin took 14 days. There was no significant difference in the duration of lowering the blood glucose by the two doses of extract administered. In conclusion, oral administration of aqueous seed extract of Aframomum melegueta has potent hypoglycaemic activity in alloxanised diabetic rats

Effect of Aqueous Extract of Nutmeg on Hyperglycaemia, Hyperlipidaemia and Cardiac Histology Associated with Isoproterenol-induced Myocardial Infarction in Rats

Purpose: The present study was designed to evaluate the hypoglycaemic and hypolipidaemic activities of the aqueous extract of nutmeg (i.e., the kernel of Myristica fragrans) in rat models against myocardial infarction (MI) induced by isoproterenol (ISO).Methods: Rats were pretreated with nutmeg extract (NM) at an oral dose of 100 mg/kg/day for a period of 30 days, followed by the induction of MI by subcutaneous administration of ISO (85 mg/kg) for two consecutive days. The heart tissue was excised immediately, washed with chilled isotonic saline and used in histopathological studies. Blood was also collected from the animals and the plasma separated was subjected to biochemical analysis.Results: In ISO-administered group, a significant (p < 0.05) increase in the levels of blood glucose, plasma lipids and lipoprotein lipase activity was observed along with hyalinization of muscle fibres, compared NM-pretreated ISO-administered rats. In rats treated with NM, biochemical parameters were near normal. Histological studies revealed reduced damage of heart tissue in ISO-administered rats that were pretreated with NM.Conclusion: NM possesses protected rats against hyperglycaemia, hyperlipidaemia and cardiac tissue damage following MI. Therefore, NM should be further investigated as a prophylactic against the risk of MI

Young neutron stars with soft gamma ray emission and anomalous X-ray pulsar

The observational properties of Soft Gamma Repeaters and Ano\-malous X-ray Pulsars (SGR/AXP) indicate to necessity of the energy source different from a rotational energy of a neutron star. The model, where the source of the energy is connected with a magnetic field dissipation in a highly magnetized neutron star (magnetar) is analyzed. Some observational inconsistencies are indicated for this interpretation. The alternative energy source, connected with the nuclear energy of superheavy nuclei stored in the nonequilibrium layer of low mass neutron star is discussed.Comment: 29 pages, 13 figures, Springer International Publishing Switzerland 2016 A.W. Alsabti, P. Murdin (eds.), Handbook of Supernova

Accretion Disc Theory: From the Standard Model Until Advection

Accretion disc theory was first developed as a theory with the local heat balance, where the whole energy produced by a viscous heating was emitted to the sides of the disc. One of the most important new invention of this theory was a phenomenological treatment of the turbulent viscosity, known as ''alpha'' prescription, when the (r$\phi$) component of the stress tensor was approximated by ($\alpha$ P) with a unknown constant $\alpha$. This prescription played the role in the accretion disc theory as well important as the mixing-length theory of convection for stellar evolution. Sources of turbulence in the accretion disc are discussed, including nonlinear hydrodynamical turbulence, convection and magnetic field role. In parallel to the optically thick geometrically thin accretion disc models, a new branch of the optically thin accretion disc models was discovered, with a larger thickness for the same total luminosity. The choice between these solutions should be done of the base of a stability analysis. The ideas underlying the necessity to include advection into the accretion disc theory are presented and first models with advection are reviewed. The present status of the solution for a low-luminous optically thin accretion disc model with advection is discussed and the limits for an advection dominated accretion flows (ADAF) imposed by the presence of magnetic field are analysed.Comment: Roceeding of the Int. Workshop "Observational Evidence for Black Holes in the Universe". Calcutta, 11-17 January 1998. Kluwer Acad. Pu