Inference of historical population-size changes with allele-frequency data

With up to millions of nearly neutral polymorphisms now being routinely sampled in population-genomic surveys, it is possible to estimate the site-frequency spectrum of such sites with high precision. Each frequency class reflects a mixture of potentially unique demographic histories, which can be revealed using theory for the probability distributions of the starting and ending points of branch segments over all possible coalescence trees. Such distributions are completely independent of past population history, which only influences the segment lengths, providing the basis for estimating average population sizes separating tree-wide coalescence events. The history of population-size change experienced by a sample of polymorphisms can then be dissected in a model-flexible fashion, and extension of this theory allows estimation of the mean and full distribution of long-term effective population sizes and ages of alleles of specific frequencies. Here, we outline the basic theory underlying the conceptual approach, develop and test an efficient statistical procedure for parameter estimation, and apply this to multiple population-genomic datasets for the microcrustacean Daphnia pulex

Comparative Analysis of Super-Kamiokande and SNO Solar-Neutrino Data and the Photospheric Magnetic Field

We analyze Super-Kamiokande, SNO, and photospheric magnetic-field data for the common time interval, namely the SNO D2O phase. Concerning rotational modulation, the magnetic-field power spectrum shows the strongest peaks at the second and sixth harmonics of the solar synodic rotation frequency [3 nu(rot) and 7 nu(rot)]. The restricted Super-Kamiokande dataset shows strong modulation at the second harmonic. The SNO D2O dataset shows weak modulation at that frequency, but strong modulation in the sixth-harmonic frequency band. We estimate the significance level of the correspondence of the Super-Kamiokande second-harmonic peak with the corresponding magnetic-field peak to be 0.0004, and the significance level of the correspondence of the SNO D2O sixth-harmonic peak with the corresponding magnetic-field peak to be 0.009. By estimating the amplitude of the modulation of the solar neutrino flux at the second harmonic from the restricted Super-Kamiokande dataset, we find that the weak power at that frequency in the SNO D2O power spectrum is not particularly surprising. Concerning 9.43 yr-1, we find no peak at this frequency in the power spectrum formed from the restricted Super-Kamiokande dataset, so it is no surprise that this peak does not show up in the SNO D2O dataset, either.Comment: 32 pages, 8 tables, 16 figure

A preliminary investigation of strains and fracturing in small hydro-stone beams due to impact loading

Every structure has a fundamental frequency which is sometimes referred to as its first natural frequency. If a periodic force acts on the structure whose frequency is equal to that of the natural frequency of the structure, a vibration is set up whose amplitude would approach infinity if it were not for the presence of damping. Since damping is always present, steady state conditions will finally be reached provided that the applied force is not so great that it will cause the structure to fail. The amplitude of the vibration will be a function of the applied force and the damping capacity of the structure. Steady state conditions will also be finally obtained if a periodic force acts on a structure whose frequency is not equal to the natural frequency of the structure. In this case, the amplitude of the vibration will be a function of the magnitude of the applied force, the damping capacity of the structure, and the ratio of the frequency of the applied force to the natural frequency. The maximum amplitude is obtained when the ratio is equal to 1. An impulse will excite vibrations also, but no steady state harmonic conditions will be obtained. Either the structure will fail or it will return back to the initial state on account of the presence of damping. The mining engineer is interested in the impact loading of structures, because this is the type of force supplied by the action of explosives. This is a preliminary investigation of the strain time history in a small hydro-stone beam due to a suddenly applied force. The impact loading was obtained by dropping steel balls from various heights on the beam. The purpose of the first part of this project was to determine the influence of a number of variables on the strain. The factors which were studied are: a variation in the height of drop and in the weight of the balls; and the effect of the size of the variable resistance wire strain gage on the dynamic strain record. The object of the second part of this project was to investigate the strains present in a small hydro-stone beam when it is subjected to an impact loading which is sufficiently large to cause the beam to fail --Introduction, pages 1-2

Statistics of selectively neutral genetic variation

Random models of evolution are instrumental in extracting rates of microscopic evolutionary mechanisms from empirical observations on genetic variation in genome sequences. In this context it is necessary to know the statistical properties of empirical observables (such as the local homozygosity for instance). Previous work relies on numerical results or assumes Gaussian approximations for the corresponding distributions. In this paper we give an analytical derivation of the statistical properties of the local homozygosity and other empirical observables assuming selective neutrality. We find that such distributions can be very non-Gaussian.Comment: 4 pages, 4 figure

Fast detection of unique genomic regions

Unique genomic regions are of particular interest in two scenarios: When extracted from a single mammalian target genome, they are highly enriched for developmental genes. When extracted from target genomes compared to closely related neighbor genomes, they are highly enriched for diagnostic markers. Despite their biological importance and potential economic value, unique regions remain difficult to detect from whole genome sequences. In this review we survey three efficient programs for the detection of unique regions at scale, genmap, macle, and fur. We explain these programs and demonstrate their application by analyzing simulated and real data. Example scripts for searching for unique regions are available from the Github repository evolbioinf/sure as part of a detailed tutorial.<br

Detection and annotation of unique regions in mammalian genomes

Long unique genomic regions have been reported to be highly enriched for developmental genes in mice and humans. In this paper we identify unique genomic regions using an efficient method based on fast string matching. We quantify the resource consumption and accuracy of this method before applying it to the genomes of 18 mammals. We annotate their unique regions of at least 10 kb and find that they are strongly enriched for developmental genes across the board. We then investigated the subset of unique regions that lack annotations, which we call “anonymous”. The longest anonymous unique region in the tasmanian devil spanned 83 kb and contained the gene encoding inositol polyphosphate-5-phosphatase A, which is an essential part of intracellular signaling. This discovery of an essential gene in a unique region implies that unique regions might be given priority when annotating mammalian genomes. Our documented pipeline for annotating unique regions in any mammalian genome is available from the repository github.com/evolbioinf/auger; additional data for this study is available from the dataverse at doi.org/10.17617/3.4IKQAG

Dinosaur tracks from the Kilmaluag Formation (Bathonian, Middle Jurassic) of Score Bay, Isle of Skye, Scotland, UK

Tracks of a juvenile theropod dinosaur with footprint lengths of between 2 and 9 cm as well as adults of the same ichnospecies with footprints of about 15–25 cm in length were found in the Bathonian (Middle Jurassic) Kilmaluag Formation of Score Bay, northwestern Trotternish Peninsula, Isle of Skye, Scotland, UK. Two footprint sizes occur together on the same bedding plane in the central portion of Score Bay, both in situ and on loose blocks. Another horizon containing footprints above this was also identified. The footprints from the lowest horizon were produced in a desiccated silty mud that was covered with sand. A close association of both adults and juveniles with similar travel direction indicated by the footprints may suggest post-hatching care in theropod dinosaurs. Other footprints, produced on a rippled sandy substrate, have been found on the slightly higher bedding plane at this locality. Loose blocks found 130 m to the northeast in the central part of Score Bay have not been correlated with any in situ sediments, but were preserved in a similar manner to those from the higher bedding plane. These tracks represent the youngest dinosaur remains yet found in Scotland