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This paper analyzes how the real part of the dielectric constant affects the emittance or temperature in some materials. A two-layer configuration was implemented on a glass substrate, with theory and experiment, on a sunny day in Mexico. Furthermore, the transfer matrix method was used as theory, changing the material on the top of the substrate and below a film of zinc sulfide. As a result, for a larger real part of the dielectric constant, the emittance decreased in analytical results, and therefore a decrease in temperature was obtained in the experiment. Furthermore, a virtual dielectric constant was obtained from the experimental reflectance in a bilayer system reproducing this system analytically with one layer having different thickness. The finite-difference time-domain (FDTD) method was used to obtain the optimal length of equilateral pyramids on the surface of a flat film by changing the materials to improve the reflectance or decrease the emittance. It was concluded that for a wavelength of the incident source, optimal dimensions of the triangles on the surface exist. [ABSTRACT FROM AUTHOR]

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Nile tilapia Oreochromis niloticus is one of the most economically important freshwater fish cultivated worldwide. Despite its importance and being one of the cichlid fish most studied from a parasitological point of view in Mexico, there are few studies about the ectoparasite protozoa that infect them. In this study, a total of 240 juvenile individuals of O. niloticus from an experimental culture (in Tabasco, Mexico) were examined to detect the presence of trichodinid parasites. Trichodinid parasites were impregnated with silver nitrate and stained with Harris´ hematoxylin solution for taxonomic evaluation. A disc-shaped trichodinid with a body diameter of 38 ± 3.3 μm adhesive disc diameter of 34 ± 3.3 μm and a denticulate ring diameter of 19 ± 2.1 μm was found. Trichodina centrostrigeata has been previously reported having specificity for cypriniform species, but in the present study, the Nile tilapia was reported as a new fish host and southeastern Mexico as a new geographical distribution for this parasite. [ABSTRACT FROM AUTHOR]

Trichodiniasis is one of the major diseases found in fish aquaculture worldwide causing massive fish mortality and costly effects. In this study, fresh smears of gills and skin were prepared and analyzed for the presence of trichodinids under light microscopy, revealing the presence of Trichodina pediculus Ehrenberg, 1831, T. compacta Van As & Basson, 1989, and T. nigra Lom, 1960 and T. centrostrigeata (Basson, Van As & Paperna, 1983). The effectiveness of treatment with sodium chloride and formaldehyde was evaluated for controlling infection caused by these parasites in tilapia Oreochromis niloticus Linnaeus, 1758 in aquaculture facilities in southeastern Mexico. A total of 240 fish were examined. The results showed that all doses using sodium were effective for controlling trichodinids and eliminated the parasites (100%) however, fish exposed to doses of formalin showed a higher level of stress than those exposed to sodium chloride. Bathing in formalin 0.250 mL L-1 for 10 min and 30 g L-1 of sodium chloride for 10 min, significantly reduced parasitic infection in tilapia under captive conditions (P < 0.05). This is the first record of a trichodinids species for native wild freshwater fish in a culture environment in southeastern Mexico since all previous records were from exotic cultured fish. The species found were Trichodina pediculus, T. compacta, T. nigra and T. centrostrigeata are new records of host and geographic location. [ABSTRACT FROM AUTHOR]