The failure of conventional quantum theory to recognize time as an observable and to admit time operators is addressed. Instead of focusing on the existence of a time operator for a given Hamiltonian, we emphasize the role of the Hamiltonian as the generator of translations in time to construct time states. Taken together, these states constitute what we call a timeline. Such timelines are adequate for the representation of any physical state, and appear to exist even for the semi-bounded and (...) discrete Hamiltonian systems ruled out by Pauli’s theorem. However, the step from a timeline to a valid time operator requires additional assumptions that are not always met. Still, this approach illuminates the issues surrounding the construction of time operators, and establishes timelines as legitimate alternatives to the familiar coordinate and momentum bases of standard quantum theory. (shrink)

Silencing of tumor suppressor genes (TSGs), by DNA methylation, is well known in adult cancers. However, based on the “stem cell” theory of tumorigenesis, the early epigenetic events arising in malignant precursors remain unknown. A recent report1 demonstrates that, while pluripotent embryonic stem cells lack DNA methylation and possess a “bivalent” pattern of activating and repressive histone marks in numerous TSGs, analogous multipotent malignant cells derived from germ cell tumors (embryonic carcinoma cells) gain additional silencing modifications to those same genes. (...) These results suggest a possible mechanism by which aberrant differentiation, mediated by histone and DNA methylation, instigates tumor progression. BioEssays 29:842–845, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Graphical AbstractScience and technology consortia provide a viable solution for the recent unsustainable academic growth in biomedical research.

Compelling evidence is presented that Glauber worked as a laborator (laboratory assistant) for Landgrave Georg of Hesse-Darmstadt from 1632/33 till he was appointed apothecary in Giessen in 1635. During this time, he was also used as laborator by the landgrave’s personal physician, Helwig Dieterich. Glauber became a famous chemist, whose alchemical secrets were keenly solicited by King Frederik III of Denmark, Queen Christina of Sweden, and, according to the 1662 diary of Ole Borch, King Charles II of England. A 1689 (...) letter to Queen Christina contains detailed descriptions of Glauber’s alkahest, his decomposition and redintegration of saltpeter, and his ‘most secret sal armoniacum’, which is interpreted here for the first time. (shrink)

Extinction deeply colors the way we think about conservation and the role of humans in nature. It is easy to overlook how recently, in fact, it has entered our consciousness. Only in the last two centuries has science sought to critically study life's origins, development, and diversification. Only in the last several generations have we identified and calibrated life's five major extinction events and speculated on their causes and effects. And only in recent decades have we come to appreciate the (...) still‐unfolding fate of life's diversity under the increasing influence of humanity. The story of extinction has continually changed as this monumental process of interdisciplinary synthesis and imagination has unfolded. Geology, paleontology, taxonomy, biogeography, and evolutionary biology have allowed us to comprehend the deep temporal and broad spatial dynamics of the extinction story. Archaeology, cultural anthropology, and environmental and economic history have illuminated the role of humans in altering the trajectory of species, landscapes, and ecosystems over the millennia. Ecology, genetics, population biology, and conservation biology have revealed the more recent patterns in life's vulnerability and resilience. As a phenomenon, extinction is as old as life itself. As a story shaping our consciousness, values, and intentions, it is still new. And it is uncomfortable. (shrink)

The stable differentiation of cells into other cell types typically involves dramatic reorganization of cellular structures and functions. This often includes remodeling of the cell cycle and the apparatus that controls it. Here we review our understanding of the role and regulation of cell cycle control elements during cell differentiation in the yeast, Saccharomyces cerevisiae. Although the process of differentiation may be more overtly obvious in metazoan organisms, those systems are by nature more difficult to study at a mechanistic level. (...) We consider the relatively well‐understood mechanisms by which mating‐type switching and the pheromone‐induced differentiation of gametes are coupled to the cell cycle as well as the more obscure mechanisms that govern the remodeling of the cell cycle during meiosis and filamentous growth. In some cases, the cell cycle is a primary stimulus for differentiation whereas, in other cases, the signals that promote differentiation alter the cell cycle. Thus, despite relative simplicity of these processes in yeast, the nature of the interplay between the cell cycle and differentiation is diverse. BioEssays 25:856–867, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

Die Autoren sind katholische Priester und stellen das christliche Menschenbild und die Ethik der Gesundheitssorge in den Mittelpunkt. Herausgearbeitet wird die ihrer Ansicht nach besondere ethische Verantwortung der Pflegekräfte in ihren Beziehungen zu Patienten, Angehörigen und Ärzten bei Fragen der Lebens- und Sterbehilfe.