The influence of the combined microwave power and hot air ventilation on the drying kinetics and colour quality of tomato slices

Tomato is one of the most important fruit used as an ingredient in different foods in food processing and preparation. Fresh tomato consists of about 91% of moisture. Tomato has to pass through all three rates of drying (constant, first and second falling rate period) during drying, using hot air ventilation, and requires prolonged time with much of quality changes. In this study, microwave assisted hot air ventilation drying of tomato slices had been considered. Microwave oven working at 2450 MHz, using different power densities (1, 2 and 3 W g-1) was combined with hot air ventilation at 50°C and hot air ventilation drying without microwave power at 40, 50, 70 and 80°C to dry tomato slices down to 10% moisture content. The drying characteristic curve was analyzed to determine the drying time. The tomato slice sample dried faster when subjected to microwave heating, coupled with hot air ventilation at 50°C. The drying times required for tomato slices to reach 10% moisture content were found to be 3.2, 2.5 and 1.3 h, using 1, 2 and 3 W g-1 microwave power densities, coupled with 50°C hot air ventilation, respectively. On the other hand, the drying time of tomato slices to 10% moisture content required 20.5, 13.1, 9.6, 6.8 h for drying at 40, 50, 70 and 80°C, using hot air ventilation without supplementing heating with microwave power. Microwave drying maintained the superior colour of tomato slices after drying period, compared to the other treatments.Key words: Microwave, tomato slice, drying equation, colour, drying rate, moisture content

Modelling the Transmission Dynamics of HIV and HBV Co-epidemics: Analysis and Simulation.

The prevalence of Hepatitis B Virus (HBV) and Human immunodeficiency virus (HIV) co-infection have been on the increase. Moreover, none of these two diseases has a cure for now while both diseases are very deadly. However, the mode of transmission of these diseases are closely related and this highly predisposes individuals to co-infection. There is, therefore, the need to initiate effective control measures that would forestall the co-epidemic of the two diseases in our society, considering the grave implications of such situation. Consequently, a deterministic model for HIV and HBV co-epidemic which unveils measures that should be implemented to avoid the menace associated with the co-epidemic is considered. The model is qualitatively analyzed and the model basic reproduction number is derived. The criteria for the stability of each of the model equilibria are established. The model is numerically solved and simulated for the different scenarios of the co-epidemic. The findings from the simulations are discussed. Keywords: Hepatitis B Virus, Human immunodeficiency virus, Co-epidemic, Disease prevalence, Equilibrium solution, Stability analysi

Learning from Nature: Unsteady Flow Physics in Bioinspired Flapping Flight

There are few studies on wing flexibility and the associated aerodynamic performance of insect wings during free flight, which are potential candidates for developing bioinspired microaerial vehicles (MAVs). To this end, this chapter aims at understanding wing deformation and motions of insects through a combined experimental and computational approach. Two sets of techniques are currently being developed to make this integration possible: first, data acquisition through the use of high-speed photogrammetry and accurate data reconstruction to quantify the wing and body motions in free flight with great detail and second, direct numerical simulation (DNS) for force measurements and visualization of vortex structures. Unlike most previous studies that focus on the near-field vortex formation mechanisms of a single rigid flapping wing, this chapter presents freely flying insects with full-field vortex structures and associated unsteady aerodynamics at low Reynolds numbers. Our chapter is expected to lead to valuable insights into the underlying physics about flow mechanisms of low Reynolds number flight in nature, which will have great significance to flapping-wing MAV design and optimization research in the future

Development of a Machine for Expressing Vernonia amygdalina Leaf Juice

Vernonia amygdalina leaf juice is known for its nutritive value and as food supplement. There is therefore, a need for a simple processing device for the leaf juice expression. This study developed a machine for producing contamination-free V. amygdalina leaf juice. The design of the machine was based on the principle of a pressure deferential applied to the incoming leaf mash compared with that applied to the discharged material. Macerated leaves were compressed through a tapered screw conveyor; whose shaft terminates as a rising but short conical kink. The maximum juice yield of 41.39% was expressed from the leaf mash at pressing pressure and residence time of 6.09 MPa and 11 min, respectively. The throughput of the machine was 9.60 kg/h and the juice extraction rate was 1.86/h at leaf to water ratio of 1: 0.8. The maximum juice expression efficiency was 15.54% at 1: 1.2 leaf to water ratio, 60 rpm constant rotational motor speed and 11.99 kg/h feeding rate. Approximately 26.38% of the inherent moisture content of the leaf was expressed by the machine. It is expected that the machine may be used to express juice from other plant leaves having comparative physical properties. The machine therefore provides a viable technique for mechanical expression of good quality V. amygdalina leaf juice.

A nebula around Nova BT Monocerotis

We report the spectroscopic discovery of nebular Hα emission around Nova BT Monocerotis. The indicated expansion distance to this system is about 1800 pc

Effect of varieties on physicochemical and pasting characteristics of water yam flours and starches

Water yam (Dioscorea alata) flour and starch of ten varieties were processed using standard wet-milling procedure prior to the determination of their physico-chemical and pasting properties. The swelling power of the samples was characterized in the category of high restricted-swelling starch (9.21 to 11.03% for flours; 9.49 to 13.80% for starches). This characteristic is desirable for the manufacture of value-added products such as noodles and composite blends with cereals. The pasting temperature (78.05 to 86.13°C, for flours; 80.38 to 86.15°C for starches) and time (4.44 to 5.17 min for flours; 4.53 to 5.17 min for starches) of test varieties indicate higher gelatinization temperature and longer cooking time. Results of analyses of physico-chemical and pasting properties indicated significant differences (P < 0.05) among the varieties. All the varieties studied gave the potentials for the manufacture of these value-added products and non-food applications of starch such as in paper and textile industries. Moreover, the results obtained in this study also show that potential exists for selecting nutritionally superior varieties of D. alata (TDa 297 and TDa 00/00194 for flour, TDa 297 and TDa 98/01183 for starch) and these varieties could be good sources of diets to its consumers and serve as food security in developing countries.Key words: Water yam, physico-chemical, pasting, flour, starch

The hydrogen lines in the high-luminosity quasar B2 1225+31

The emission lines Hɑ, Hβ + [O III], and Lɑ have been observed in the high-redshift quasar 1225+31. The ratios of line intensities in 1225+31 are found to be Lɑ/Hɑ ~ 0.8, Hɑ/(Hβ + [O III]) ~ 4, and 4 < Hɑ/Hβ < 10. The observed value of Lɑ/Hɑ agrees well with the ratio derived by Baldwin on the basis of a composite quasar spectrum, and with direct determination of this ratio in 3C 273 and PKS 0237-23. The ratio Hɑ/Hβ is in the range of values found for a sample of low-redsh1ft quasars by Baldwin. The low value for the Lɑ/Hɑ ratio cannot be reasonably explained by foreground extmction between the Sun and 1225+31

Low resolution infrared spectra of quasars

Low resolution spectra of a significant sample of quasars show that the Paschen α and Balmer line ratios do not agree with the radiative recombination case B result and vary widely within the quasars sampled. The range in Pα:Hβ ratios is a factor of ~6, while the range in Lyα:Hα ratios is a factor of ~5. For the Pα:Balmer series, the deviations from case B recombination are not consistent with reddening, but appear, within large dispersions, to be consistent with optical depth effects in the Balmer lines affecting the line ratios. The Lyα:Hα ratio is, however, correlated with the continuum spectral index, and can be explained as due to reddening affecting both the lines and continuum