The Stern-Gerlach Experiment Revisited

The Stern-Gerlach-Experiment (SGE) of 1922 is a seminal benchmark experiment of quantum physics providing evidence for several fundamental properties of quantum systems. Based on today's knowledge we illustrate the different benchmark results of the SGE for the development of modern quantum physics and chemistry. The SGE provided the first direct experimental evidence for angular momentum quantization in the quantum world and thus also for the existence of directional quantization of all angular momenta in the process of measurement. It measured for the first time a ground state property of an atom, it produced for the first time a `spin-polarized' atomic beam, it almost revealed the electron spin. The SGE was the first fully successful molecular beam experiment with high momentum-resolution by beam measurements in vacuum. This technique provided a new kinematic microscope with which inner atomic or nuclear properties could be investigated. The original SGE is described together with early attempts by Einstein, Ehrenfest, Heisenberg, and others to understand directional quantization in the SGE. Heisenberg's and Einstein's proposals of an improved multi-stage SGE are presented. The first realization of these proposals by Stern, Phipps, Frisch and Segr\`e is described. The set-up suggested by Einstein can be considered an anticipation of a Rabi-apparatus. Recent theoretical work is mentioned in which the directional quantization process and possible interference effects of the two different spin states are investigated. In full agreement with the results of the new quantum theory directional quantization appears as a general and universal feature of quantum measurements. One experimental example for such directional quantization in scattering processes is shown. Last not least, the early history of the `almost' discovery of the electron spin in the SGE is revisited.Comment: 50pp, 17 fig

Monkey-based Research on Human Disease: The Implications of Genetic Differences

Assertions that the use of monkeys to investigate human diseases is valid scientifically are frequently based on a reported 90–93% genetic similarity between the species. Critical analyses of the relevance of monkey studies to human biology, however, indicate that this genetic similarity does not result in sufficient physiological similarity for monkeys to constitute good models for research, and that monkey data do not translate well to progress in clinical practice for humans. Salient examples include the failure of new drugs in clinical trials, the highly different infectivity and pathology of SIV/HIV, and poor extrapolation of research on Alzheimer’s disease, Parkinson’s disease and stroke. The major molecular differences underlying these inter-species phenotypic disparities have been revealed by comparative genomics and molecular biology — there are key differences in all aspects of gene expression and protein function, from chromosome and chromatin structure to post-translational modification. The collective effects of these differences are striking, extensive and widespread, and they show that the superficial similarity between human and monkey genetic sequences is of little benefit for biomedical research. The extrapolation of biomedical data from monkeys to humans is therefore highly unreliable, and the use of monkeys must be considered of questionable value, particularly given the breadth and potential of alternative methods of enquiry that are currently available to scientists

Ellen Clark, Toledo, Ohio [approximately 1890]

A cabinet card portrait of Ellen Clark once displayed by the Ford Post Number 14 of the Grand Army of the Republic (G.A.R.). The Ford Post was established in Toledo in 1867 as an organization for Union veterans of the American Civil War. Ms. Clark was a member of the Ford Circle, the ladies' G.A.R. division. Terms associated with the photograph are: Clark, Ellen | military decorations | Grand Army of the Republic. Ford Post No.14 (Toledo, Ohio) | United States--History--Civil War, 1861-186

New and little known marine nematodes from a Scottish sandy beach

13 spp of freeliving marine nematodes from the sandy beach at Firemore Bay, Wester-Ross, Scotland, are described. Amongst these the authors have proposed one gen.n., Gairleanema, with the type sp G /anagremilae gen et sp.n. 11 others are sp.n.referable to existing gen: Odontophora exharena sp.n., Theristus (Daptonema) gelana sp.n., Cobbia caledonia sp.n., Gonionchus inaequalis sp.n., Xyala smo sp.n., Siphonolaimus ewensis sp.n., Metachromadora (Bradylaimus) scotlandica sp.n., Microlaimus acinaces sp.n., Dasynemella albaensis sp.n., Rhabdodemania imer sp.n., and Triliptium parisetum sp.n. 1 sp (Trefusia zostericola Allgen. 1933) is redescribed, since it was hitherto poorly known