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The case report of a 21 years primigravida woman is presented to whom a monoamniotic and monochorial twin pregnancy was detected in the echographic exam at the Genetic Provincial Center of Santiago de Cuba. The first fetus presented bilateral hydronephrosis predominantly in the left side, and the second rudimentary and deformed fetal structure, not well structured heart area and just arrhythmic and bradycardiac heart beats besides that the internal organs were not defined and everything was surrounded by severe cystic lymphangioma with big paravertebral cysts and a single umbilical cord with three vessels. Everything described in the echogram was corroborated with the results of the autopsy, which corresponded with Acardius mylacephalus variety. [ABSTRACT FROM AUTHOR]

The effect of flame-wall interactions on the forced response of a lean-premixed, swirl-stabilized flame is experimentally investigated by examining flames in a series of three combustors, each with a different diameter, and therefore a different degree of lateral confinement. The confinement ratios tested are 0.5, 0.37, and 0.29 when calculated using the diameter of the nozzle relative to the combustor diameter. Using both flame images and measured flame transfer functions (FTFs), the effect of confinement is investigated and generalized across a broad range of operating conditions. The major effect of confinement is shown to be a change in flame structure in both the forced and unforced cases. This effect is captured using the parameter Lf,CoHR/Dcomb, which describes the changing degree of flame-wall interaction in each combustor size. The measured FTF data, as a function of confinement, are then generalized by Strouhal number. Data from the two larger combustors are collapsed by multiplying the Strouhal number by the confinement ratio to account for the flow expansion ratio and change in convective velocity within the combustor. Trends at the transfer function extrema are also assessed by examining them in the context of confinement and by using flame images. A change in the fluctuating structure of the flame is also seen to result from an increase in confinement. [ABSTRACT FROM AUTHOR]

Fluctuations in the heat release rate that occur during unstable combustion in lean premixed gas turbine combustors can be attributed to velocity and equivalence ratiofluctuations. For a fully premixed flame, velocity fluctuations affect the heat release rate primarily by inducing changes in the flame area. In this paper, a technique to analyze changes in flame area using chemiluminescence-based flame images is presented. The technique decomposes the flame area into separate components which characterize the relative contributions of area fluctuations in the large scale structure and the small scale wrinkling of the flame. The fluctuation in the wrinkled area of the flame which forms the flame brush is seen to dominate its response in the majority of cases tested. Analysis of the flame area associated with the large scale structure of the flame resolves convective perturbations that move along the mean flame position. Results are presented that demonstrate the application of this technique to both single-nozzle and multi-nozzle flames. [ABSTRACT FROM AUTHOR]

We prove that an almost $$2$$ -perfect $$6$$ -cycle system of order $$n$$ exists if and only if $$n \equiv 1$$ or $$9\ (mod\ 12)$$ , and that an almost $$2$$ -perfect maximum packing with $$6$$ -cycles of order $$n$$ exists for all $$n \ge 6$$ . [ABSTRACT FROM AUTHOR]