4,552 publications from this institution
Antonin Holý (1936–2012) After a long, incapicitating illness due to the complications of Parkinson's disease, Antonin Holý passed away on July 16, 2012, at his home in Prague. He was born on September 1, 1936 in Prague (at the time, Czechoslovakia) where he would also graduate in 1959 as an organic chemist, and spend his whole life at the Institute of Organic Chemistry and Biochemistry (IOCB), from 1994 to 2002, as its Director. Dr. Holý was honored several times with prestigious awards in his home country, the Czech Republic, and obtained honorary degrees from the Universities of Olomouc (Czech Republic), České Budéjovice (Czech Republic), Ghent (Belgium), and Manchester (United Kingdom). The pioneering work of Dr. Holý was concentrated on the acyclic nucleoside phosphonates, which conquered a key position in the treatment of AIDS, hepatitis B, herpes, and poxvirus infections. The basic discovery of this class of compounds was published 26 years ago in Nature (1986;323:464–467) and would be the subject of another Nature paper in 2006 (2006;439:745–748). Dr. Holý laid the basis for a number of antiviral drugs (Vistide®, Hepsera®, Viread®, Truvada®, Atripla®, Complera®, and StribildTM mainly for the treatment of AIDS and hepatitis B. Truvada was as the first anti-HIV drug ever, approved for the prophylaxis of HIV infections, by the US FDA on July 16, 2012, exactly the same day that Dr. Holý died. Through his discoveries, Antonin Holý contributed to saving the lives of millions of people worldwide by protecting them from such widespread diseases as AIDS and hepatitis B. With his discovery of the acyclic nucleoside phosphonates (Nat Rev Drug Discov 2005;4:928–940), Holý added a new dimension to the therapy of AIDS, which, now that Truvada has been approved for the prophylaxis of HIV, as well, may be heralded as a step forward in the eventual eradication of the disease. Holý was a reserved, humble scientist, soft spoken even before, due to his illness, his voice completely faded away. He was a gifted, highly productive chemist, who only had one passion in life—change the world with medically useful drugs, whether antiviral or antitumoral. His molecules have changed the world of the antivirals. In the Czech Republic, Holý has entered the hall of fame, only preceded by other Czech heroes such as Gregor Mendel (the founder of genetics), Jaroslav Heyrovský (the discoverer of polarography), and Otto Wichterle (the pioneer of the soft lens). The Czech Republic should be proud of counting Antonin Holý as one of theirs, and so should be all of us who have known Dr. Holý as a Chemist, a Scientist and a Friend. With Dr. Holý, not only the Czech Republic, but the whole world has lost a true captain of research, a great inventor and innovator, and a real statesman of Science.
3',3'-Difluoro-3'-deoxythymidine (3) has been synthesized in four steps from thymidine, and characterized by 1H NMR and NOE experiments. The JHF coupling constants support a conformation in solution that is predominantly 2'-endo (S). Although conformationally and sterically nucleoside 3 may resemble other thymidine analogs which are active against HIV-1, 3 is virtually inactive.
Selective laser melting of pure copper is challenging because of its high optical reflectivity and thermal conductivity. Accordingly, the surface of pure copper powder was modified by oxidation to enhance the optical absorption. The powder with improved optical absorption facilitated the production of crack-free and dense copper parts at relatively lower laser energy density in both argon and nitrogen atmosphere. The microstructural analysis demonstrated the presence of stable melt tracks without obvious porosity. A very high electrical conductivity of approximately 89% of the international annealed copper standard, the hardness of approximately 93 HV, a tensile strength of approximately 270 MPa, and ductility of approximately 28% were achieved in the as-built condition.
Today’s software for laser-based additive manufacturing compensates for the finite dimensions of the laser spot by insetting the contours of a solid part. However, features having smaller dimensions are removed by this operation, which may significantly alter the structure of thin-walled parts. To avoid potential production errors, this work describes in detail an algorithmic framework that makes beam compensation more reliable by computing laser scan paths for thin features. The geometry of the features can be adjusted by the scan paths by means of five intuitive parameters, which are illustrated with examples. Benchmarks show that the scan path generation comes at a reasonable cost without altering the computational complexity of the overall beam compensation framework. The framework was applied to Selective Laser Melting (SLM) to demonstrate that it can significantly improve the robustness of additive manufacturing. Besides robustness, the framework is expected to allow further improvements to the accuracy of additive manufacturing by enabling a geometry-dependent determination of the laser parameters.
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