Though only recently established, this concept has been developing for a long time. More than thirty years ago Dubinin, Serebrovsky, and other, investigating the phenotypes of a number of "achaete-scute" alleles of Drosophilia melanogaster, found that the alleles could be arranged in a definite series accoding to bristle patters, and also that the heterozygotes lacked only those bristles which were affected in common by both participating alleles. They concluded that the serial classification of alleles according to bristle patters had its counterpart in a similar arrangement of portions of the achaete-scute gene locus. On this assumption they divided the locus into twelve elementary subunits. It was assumed that each allele arose by a change involving a certain combination of these centres. According to their theory, the achaete-scute locus is made up of separate, regularly spaced, and linearly arranged functional units. Several years later, Oliver described the occurrence of crossing over between two alleles of the "lozenge" locus. Then Green and a number of other workers analyzed similar phenomena in different regions of Drosophila chromosome. During the same period Lewis developed the theory of pseudoallelism, which interprets the occurrence of recombinants in interallelic crosses as the result of gene duplications. Thus …

One of the more apparent differences between acute and chronic irradiation is that exposure in the former is generally confined to a small fraction of a single mitotic cycle while in the latter; exposure of mitotically active tissue usually involves at least several cycles. Because of this difference, the number of cells in each stage of interphase would be of primary importance in acute radiation experiments since radiosensitivity is not the same in the G1, S and G2 periods. The duration of the total mitotic cycle should be more important in chronic experiments because most of the cells in the tissue will have passed through each of the interphase stages (G1, S and G2) during the period of irradiation thus negating any different effect.

Treatment of Pisum root meristems with nutrient solutions containing tritiated thymidine (H3-T) and colchicine simultaneously labeled cells in two different segments of the mitotic cycle. Tracings of the serial progression of these differently labeled cells through mitosis resembled sine-cosine curves. When the labeled cells are in interphase the sign of the curves is negative, when they are in mitosis the sign is positive. The concept of the mitotic cycle in terms of trigonometric functions was presented as one way of transferring cycle from a celestial time scale to that of a biological clock.

Recently, we reported that the administration of the thyroid hormone, L-triiodothyronine (T3), markedly accelerated the development of experimental hypertension associated with a high-salt intake in intact rate. Earlier, Selye and his associates and Masson, Corcoran, and Page has observed a similar effect from thyroxin in uninephrectomized salt-fed rats. We were aware of the fact that oxidative phosphorylation is uncoupled by the thyroid hormone and were intrigued by the possibility that such uncoupling was instrumental in the accelerated development of the hypertension observed. The work reported here was undertaken with this possibility in mind; it was based on the well documented observation of Loomis and Lipmann that dinitrophenol reversibly inhabits oxidative phosphorylation. The present studies indicates that 2, 4-dinitrophenol, like L-triiodothyronine, can also rapidly induce hypertension in salt-fed rate. These observations have led us to develop a working hypothesis that may have general implications relative to the pathogenesis of hypertension in man.

An additive, interacting mechanism of micro and macro-convective heat transfer is proposed to represent boiling heat transfer with net vapor generation to saturated liquid metals in convective flow. Based on this mechanism, a method for calculating boiling coefficients is developed. The correlating is shown to be in fair agreement with early experimental results for convective boiling of potassium and sodium.

The vibrational spectra between 1000 and 30 cm-1, derived from measurements of the inelastic scattering of "cold" neutrons, are presented for isotactic polypropylene at samples temperatures below and above both the glass transition and the melting point. A tentative assignment of the observed modes is suggested by comparison with recent calculations by Miyazawa, Ideguchi, and Fukushima of the optically active phases of the fundamental vibrations for an isotactic helical polypropylene chain and with the neutron measurements of the low frequency modes in highly-crystalline polyethylene. In addition to the skeletal optical modes, the neutron spectra for isotactic polypropylene indicate the existence of two acoustic modes - skeletal deformation and skeletal torsion - with high frequency limits at 620 ± 50 cm-1 and 110 ± 10 cm-1, respectively. As in polyethylene, these modes appear to be strongly influenced by the presence and phase of the disorder in the sample. Similar spectra for atactic polypropylene above and below the glass transition show a much less pronounced structure, although weak bands are observed which correlate well with the skeletal optical modes observed in the isotactic polymer.