Febrile Convulsions as a Problem in Waiting Times

A simple hypothesis on the occurrence of febrile convulsions is posed. This is (1) that certain children are genetically predisposed, and (2) that for such children, the probability of the first attack occurring in year 1, 2, etc., is essentially constant up to the end of the period during which the attacks can take place. These assumptions lead to a probability model which agrees well with data on age at first attack in the Town of Tecumseh, Mich. It appears that susceptibility does not gradually diminish, but rather disappears abruptly. The calculation yields an estimate of the proportion of children, among those susceptible, who will have at least one attack before they exceed the age of suceptibility. Penetrance of the condition, measured in this way, is nearly complete: 93.8% will have manifested the condition by age 7. The population frequency of the susceptible type of child is found to be 3.90%. If one assumes the simple dominant mode of inheritance of Frantzen et al. to be correct, this estimate of population frequency leads to an estimate of the gene frequency. This is approximately p = 0.02. The homozygote would therefore have a frequency of 4 per 10,000. Some speculations on verifying this theory of inheritance by identifying the homozygote are given. RÉSUMÉ On Émet une hypothÈse simple sur la survenue des convulsions fÉbriles, À savoir (1) que certains enfants sont gÉnÉtiquement prÉdisposÉs et (2) que pour ces enfants la probabilitÉ d'apparition de la premiÈre crise dans la premiÈre, la seconde annÉe, etc. est essentiellement constante jusqu'À la fin de la pÉriode pendant laquelle les crises peuvent survenir. De telles suppositions conduisent ÀÉtablir un modÈle de probabilite qui concorde bien avec les donnÉes sur l'Âge de la premiÈre crise, dans la ville de Techumseh, dans le Michigan. Il en ressort que cette prÉdisposition ne diminue pas progressivement, mais au contraire, disparaÎt brusquement. Les calculs permettent d'estimer la proportion d'enfants prÉdisposÉs qui auront au moins une crise, avant d'avoir dÉpassÉ l'Âge limite de la prÉdisposition. La pÉnÉtrance de cette condition, ainsi ÉvaluÉe, est presque complÈte: 93.8% des enfants auront manifestÉ cette condition À l'Âge de 7 ans. La frÉquence des enfants prÉdisposÉs dans la population est de 3.90%. Si l'on considÈre que le mode d'hÉrÉditÉ dominante simple de Frantzen est valable, cette estimation de la frÉquence dans la population conduit À une Évaluation de la frÉquence du gÈne. Celle-ci est approximativement de p = 0.02; l'homozygote aurait done une frÉquence de 4/10.000. Les possibilitÉs de vÉrifier cette thÉorie des modalitÉs hÉrÉditaires par l'identification de l'homozygote sont discutÉes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65705/1/j.1528-1157.1972.tb05265.x.pd

Impact cratering and the Oort cloud

We calculate the expected flux profile of comets into the planetary system from the Oort cloud arising from Galactic tides and encounters with molecular clouds. We find that both periodic and sporadic bombardment episodes, with amplitudes an order of magnitude above background, occur on characteristic timescales ~25-35 Myr. Bombardment episodes occurring preferentially during spiral arm crossings may be responsible both for mass extinctions of life and the transfer of viable microorganisms from the bombarded Earth into the disturbing nebulae. Good agreement is found between the theoretical expectations and the age distribution of large, well-dated terrestrial impact craters of the past 250 million years. A weak periodicity of ~36 Myr in the cratering record is consistent with the Sun's recent passage through the Galactic plane, and implies a central plane density ~0.15 M_Sun pc^(-3). This leaves little room for a significant dark matter component in the disc

Synthetic redesign of plant lipid metabolism

Plant seed lipid metabolism is an area of intensive research, including many examples of transgenic events in which oil composition has been modified. In the selected examples described in this review, progress towards the predictive manipulation of metabolism and the reconstitution of desired traits in a non-native host is considered. The advantages of a particular oilseed crop, Camelina sativa, as a flexible and utilitarian chassis for advanced metabolic engineering and applied synthetic biology are considered, as are the issues that still represent gaps in our ability to predictably alter plant lipid biosynthesis. Opportunities to deliver useful bio-based products via transgenic plants are described, some of which represent the most complex genetic engineering in plants to date. Future prospects are considered, with a focus on the desire to transition to more (computationally) directed manipulations of metabolism

A method to simulate inhomogeneously irradiated objects with a superposition of 1D models

In close binary systems the atmosphere of one or both components can be significantly influenced by irradiation from the companion. Often the irradiated atmosphere is simulated with a single-temperature approximation for the entire half-sphere. We present a scheme to take the varying irradiation angle into account by combining several separate 1D models. This is independent of the actual code which provides the separate stellar spectra. We calculate the projected area of zones with given irradiation angle and use this geometrical factor to scale separate 1D models. As an example we calculate two different irradiation scenarios with the PHOENIX code. The scheme to calculate the projected area is applicable independent of the physical mechanism that forms these zones. In the case of irradiation by a primary with T=125000 K, the secondary forms ions at different ionisation states for different irradiation angles. No single irradiation angle exists which provides an accurate description of the spectrum. We show a similar simulation for weaker irradiation, where the profile of the H$\alpha$ line depends on the irradiation angle.Comment: published in A&

Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions

As part of our campaign to determine the nature of the various source populations of the low-luminosity globular cluster X-ray sources, we have obtained a Chandra X-ray Observatory ACIS-S3 image of the globular cluster NGC 6440. We detect 24 sources to a limiting luminosity of ~2 times 10^31 erg/s (0.5-2.5keV) inside the cluster's half-mass radius, all of which lie within ~2 core radii of the cluster center. We also find excess emission in and around the core which could be due to unresolved point sources. Based upon X-ray luminosities and colors, we conclude that there are 4-5 likely quiescent low-mass X-ray binaries and that most of the other sources are cataclysmic variables. We compare these results to Chandra results from other globular clusters and find the X-ray luminosity functions differ among the clusters.Comment: 9 pages, 4 figures, accepted by ApJ, minor changes, added table of clusters' physical parameter