The use of chemicals gradually increased from prehistoric time to the fourth century A.D. when alchemy was introduced. Alchemy was a branch of chemistry that attempted to transform base metals (eg, lead, copper, and zinc) to precious metals (eg, silver and gold) [1]. Alchemists pursued this futile goal with secretive stubbornness for over a thousand years, to the detriment of chemistry as a who...

Michael Polanyi (1891-1976) marks a turn in human perspective parallel to and as significant as the turn from the Ptolemaic to the Copernican angle of vision. The Ptolemaic way of viewing the world is named after Claudius Ptolemy, one of the great geographers and astronomers of the Graeco-Roman period, who was active in Alexandria, Egypt, in the Second Century of the Christian Era. In Ptolemy’s...

Niels Stensen (1638-1686) was born in Copenhagen. He took courses in medicine at the local university under the guidance of Professor Thomas Bartholin and later at Leiden under the tutelage of Franz de la Boë (Sylvius). While in Holland, he discovered the existence of the parotid duct, which was named Stensen's duct or stenonian duct (after his Latinized name Nicolaus Stenon). He also described...

We present a case study of validating an astrophysical simulation code. Our study focuses on validating FLASH, a parallel, adaptive-mesh hydrodynamics code for studying the compressible, reactive flows found in many astrophysical environments. We describe the astrophysics problems of interest and the challenges associated with simulating these problems. We describe methodology and discuss solut...

Introduction. The aortic isthmus is a specific feature of fetal circulation. It undergoes regression by becoming wider postpartum. Developmental abnormalities of an isthmus may lead to congenital defects. Aim. The aim of this work was a morphometric study of the aortic isthmus in human fetuses aged between 4 and 8 months of fetal life. Materials and methods. We investigated 223 human fetuses, i...

As a redhead I have had a personal interest in red hair, freckles and sunburns since childhood. An observation of a formaldehyde-induced fluorescence in human epidermal melanocytes initiated my scientific interest in these cells. Prota and Nicolaus demonstrated that oxidation products of cysteinyldopas are the main components of pheomelanin. Our identification of 5-S-cysteinyldopa as the source...

This paper deals with periodic solutions of the Hamilton equation ẋ(t) = J∇xH(x(t), λ), where H ∈ C2,0(R2n × Rk,R) and λ ∈ Rk is a parameter. Theorems on global bifurcation of solutions with periods 2π j , j ∈ N, from a stationary point (x0, λ0) ∈ R2n × Rk are proved. ∇xH(x0, λ0) can be singular. However, it is assumed that the local topological degree of ∇xH(·, λ0) at x0 is nonzero. For system...

Introduction. The anatomy and role of the aorta in prenatal life differ from those in postnatal life. Aim. We aimed at investigating the development of the aorta during a period between the 4th and 8th months of fetal life. We also analyzed the influence of sex on the values of the parameters examined. Materials and methods. We examined the diameters of aortas in 223 human fetuses, including 10...