Application of ultrasonic waves has been considerably progressed during the last decade and piezoelectric ceramics have had a common use as the driving source of such waves. However, there is not enough documented information on design and technology of manufacturing a high power ultrasonic transducer. In this paper, an attempt has been made to analyze the stress produced along the oscillating PZT employed ultrasonic head by applying the principles of acoustic wave propagation. Then, based on such analysis, general principles of PZT transducer design, excited by a DC-biased alternating electrical source, has been derived and finally a typical such transducer has been designed, manufactured and tested. By employing finite element modal analysis, the resonance frequency of the transducer was determined and compared with the experimental results. It was concluded that, the constitutive piezoelectric equations referred to in most sources and books are not valid for analyzing the acoustical dynamic stress in ultrasonic transducers. Instead, the analysis should be done with considering the dynamic behavior (elastic, damping and Inertia factors) of the problem.

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Dosage compensation in humans - ensuring the viability and fitness of females, with two X chromosomes, and males, with one - is thought to be achieved chromosome-wide by heterochromatinization of one X chromosome during female development. We reassessed this through quantitative gene-by-gene analyses of expression in individuals with one to four X chromosomes, tolerance for loss-of-function mutations, regulation by miRNAs, allele-specific expression, and the presence of homologous genes on the Y chromosome. We found a mosaic of dosage compensation strategies on the human X chromosome reflecting gene-by-gene differences in multiple dimensions, including sensitivity to under- or over-expression. These insights enrich our understanding of Turner, Klinefelter, and other sex chromosome aneuploidy syndromes, and of sex-chromosome-mediated effects on health and disease in euploid males and females.

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