Micrometer-Thin Crystalline-Silicon Solar Cells Integrating Numerically Optimized 2-D Photonic Crystals

A 2-D photonic crystal was integrated experimentally into a thin-film crystalline-silicon solar cell of 1-{\mu}m thickness, after numerical optimization maximizing light absorption in the active material. The photonic crystal boosted the short-circuit current of the cell, but it also damaged its open-circuit voltage and fill factor, which led to an overall decrease in performances. Comparisons between modeled and actual optical behaviors of the cell, and between ideal and actual morphologies, show the global robustness of the nanostructure to experimental deviations, but its particular sensitivity to the conformality of the top coatings and the spread in pattern dimensions, which should not be neglected in the optical model. As for the electrical behavior, the measured internal quantum efficiency shows the strong parasitic absorptions from the transparent conductive oxide and from the back-reflector, as well as the negative impact of the nanopattern on surface passivation. Our exemplifying case, thus, illustrates and experimentally confirms two recommendations for future integration of surface nanostructures for light trapping purposes: 1) the necessity to optimize absorption not for the total stack but for the single active material, and 2) the necessity to avoid damage to the active material by pattern etching.Comment: Authors' postprint version - Editor's pdf published online on Nov.

Professor Nicolas Taptas (1871-1955): A pioneer of post-laryngectomy voice rehabilitation

Objective: To report on the career of Professor Nicolas Taptas of Constantinople (1871-1955) and his contribution to the development of an artificial larynx. Study Design: Historical review. Methods: The unpublished documents of Taptas’s family archives and one of his papers, describing his own original technique for voice rehabilitation after total laryngectomies, were studied. Results: In his texts, Taptas described the application of external laryngeal prostheses in one of his patients who underwent total laryngectomy. Taptas meticulously recorded his own first successful attempt in a woman with cancer of the larynx. He was one of the first scientists who, at the end of the 19th century, devised an external laryngeal prosthesis, which had the advantage of rehabilitating a sufficiently strong whispering voice; by using a prototype valve, he avoided problems of aspiration of liquids and food to the bronchi. Conclusion: Nicolas Taptas’s contribution to the development of the artificial larynx was vital because he devised and applied one of the first external laryngeal artificial prostheses with satisfactory functional results

Semen and the diagnosis of infertility in Aristotle

Aristotle (384-322bc) was one of the leading intellectual figures of all time. In his work he systematised a massive amount of knowledge on a diverse range of subjects, including medicine. This article discusses the observations and hypotheses of this great philosopher on semen and infertility, as they are presented in his work Generation of Animals. This is combined with an evaluation of his positions in relation to those of the Hippocratic Corpus on the same subject. An extensive review of Aristotle's work Generation of Animals was performed with particular focus on his perspectives about semen and infertility. Publications referring to this work were also reviewed. According to Aristotle, semen is that which contains the principles that come from both parents when they unite. He believed that semen was formed by the secretion of nutriments by the body, developing his theories of sterility on this basic principle. A lack of fertility is attributed to genetic or acquired causes. He proposed methods for diagnosing sterility, primarily the 'water test' for men and the 'pessary' method for women. Even if his observations contain clear mistakes, such as attributing only secondary functions to male testicles and the identification of menses as women's 'seed', Aristotle's views also contain keen observations and exceptional thinking, both on the characteristics of semen and the causes of sterility (infertility).Andrologi

Fetal MRI: Is it really helpful

Objective: The aim of this study is to emphasize on the diagnostic effectiveness of fetal MRI that led to increased utilization in fetal medicine as well as its value in prognosis and decision making in the modern obstetric practice. Methods: One hundred five (n = 105) pregnant women were referred for a fetal MRI examination after a high detailed ultrasound examination revealed a fetal abnormality. Fetal MRI was performed using 1, 5 Tesla units, with T1, T2-weighted and diffusion-weighted images. The findings were analyzed in comparison to the previous ultrasound findings, according to the fetal organ affected and the value of the MRI for therapeutic decision making was addressed. A statistical analysis was performed. Results: The fetal MRI provides a more accurate diagnosis compared to ultrasound examination, and when the ultrasound detects fetal anomalies, the MRI can efficiently either confirm or reject the finding, proving its high value for prenatal diagnosis and perinatal and management. The sensitivity, specificity and positive predictive value of fetal MRI as a screening tool approaches 100%. Conclusions: Despite the fact that ultrasound is the method of choice for fetal screening, MRI can add up significantly to the diagnosis and management of congenital abnormalities and the indications for MRI continue to increase as new sequences and shorter acquisition times evolve. © 2012 Informa UK, Ltd