Rotation and mass of the sa galaxy, ngc 681

Rotation curve, mass distribution, and mass density of SA galaxy, NGC 68

Experimental application of FRF-based model updating approach to estimate soil mass and stiffness mobilised under pile impact tests

The dynamic response of structures in contact with soil is receiving increasing interest and there is a growing need for more accurate models capable of simulating the behaviour of these systems. This is particularly important in the field of offshore wind turbines, where accurate estimates of system frequency are needed to avoid resonance, and in the structural health monitoring fields, where accurate reference damage models are used. Previous work has shown that there is significant uncertainty in how to specify mobilised soil stiffness for dynamic soil-pile interaction modelling. Moreover, the contribution of soil mass in dynamic motion is often ignored. This paper applies a finite-element iterative model updating approach previously developed by the authors to two experimental piles to ascertain the mobilised soil stiffness and mass profiles from impact test data. The method works by obtaining a frequency response function (FRF) from an impact test performed on a test pile, developing a numerical model of this system, applying initial estimates of soil mass and stiffness, and updating these properties to match the experimental FRF with that generated in the numerical model. A range of elements are investigated including multiple runs of the approach to test repeatability, the influence of different starting estimates for stiffness, the effect of variability in experimental test data, and the influence of the pile length over which masses are distributed. Moreover, potential sources of error are discussed. The method provides reasonably consistent estimates of the soil stiffness and mass acting in the lateral dynamic motion of a given pile tested in this paper. The approach may be useful in the continued improvement of Soil-Structure Interaction (SSI) modelling for dynamic applications

Pervasive Neglect of Sex Differences in Biomedical Research

Females have long been underrepresented in preclinical research and clinical drug trials. Directives by the U.S. National Institutes of Health have increased female participation in research protocols, although analysis of outcomes by sex remains infrequent. The long-held view that traits of female rats and mice are more variable than those of males is discredited, supporting equal representation of both sexes in most studies. Drug pharmacokinetic analysis reveals that, among subjects administered a standard drug dose, women are exposed to higher blood drug concentrations and longer drug elimination times. This contributes to increased adverse drug reactions in women and suggests that women are routinely overmedicated and should be administered lower drug doses than men. The past decade has seen progress in female inclusion, but key subsequent steps such as sex-based analysis and sexspecific drug dosing remain to be implemented

Enhancement and Suppression of Ultradian and Circadian Rhythms Across the Female Hamster Reproductive Cycle

The impact of ovarian hormones on hamster ultradian rhythms (URs) is unknown. We concurrently monitored URs and circadian rhythms (CRs) of home cage locomotor activity during the estrous cycle, pregnancy, and lactation of Syrian hamsters. URs with a mean period of 4–5 h were evident during the dark phase in more than 90% of females on days 1 and 2 of the estrous cycle but were significantly less prevalent on cycle days 3 and 4. The period of the UR did not vary as a function of estrous cycle stage, but at all stages, the UR period was longer in the dark than the light phase. The UR acrophase occurred significantly earlier on cycle day 4 than on days 1 and 2, and UR robustness and amplitude were reduced on days 3 and 4. Robustness, mesor, and amplitude of CRs were greater during cycle days 3 and 4; timing of the CR acrophase was delayed on day 4 relative to all other cycle days. Effects of the estrous cycle on URs were evident only during the dark phase. The proportion of hamsters displaying dark phase URs increased significantly during early and late gestation and decreased during lactation. Pregnancy significantly increased UR complexity, robustness, and amplitude. The emergence of URs over gestation was paralleled by decrements in the robustness and amplitude of CRs, which also were absent in a significant proportion of dams during lactation but re-emerged at weaning of litters. The changing endocrine profile of the estrous cycle, hormonal dynamics of pregnancy and lactation, and nursing demands placed on dams are each associated with alterations in the expression of ultradian and circadian locomotor rhythms. Diminution of CRs and augmentation of URs may afford greater behavioral flexibility during life stages when interactions with mates and offspring are less predictable

Super-Eddington Atmospheres that Don't Blow Away

We show that magnetized, radiation dominated atmospheres can support steady state patterns of density inhomogeneity that enable them to radiate at far above the Eddington limit, without suffering mass loss. The inhomogeneities consist of periodic shock fronts bounding narrow, high-density regions, interspersed with much broader regions of low density. The radiation flux avoids the regions of high density, which are therefore weighed down by gravity, while gas in the low-density regions is slammed upward into the shock fronts by radiation force. As the wave pattern moves through the atmosphere, each parcel of matter alternately experiences upward and downward forces, which balance on average. Magnetic tension shares the competing forces between regions of different densities, preventing the atmosphere from blowing apart. We calculate the density structure and phase speed of the wave pattern, and relate these to the wavelength, the density contrast, and the factor by which the net radiation flux exceeds the Eddington limit. In principle, this factor can be as large as the ratio of magnetic pressure to mean gas pressure, or the ratio of radiation pressure to gas pressure, whichever is smaller. Although the magnetic pressure must be large compared to the mean gas pressure in order to support a large density contrast, it need not be large compared to the radiation pressure. These highly inhomogeneous flows could represent the nonlinear development of the "photon bubble" instability discovered by Gammie. We briefly discuss the applicability of these solutions to astrophysical systems.Comment: 11 pages, 1 figure, accepted for publication in The Astrophysical Journa

An investigation into the effect of scour on the natural frequency of an offshore wind turbine

Rapid expansion of the offshore wind industry has stimulated a renewed interest in the behaviour of offshore piles. There is widespread acceptance in practice that pile design methods developed for the offshore oil and gas industry may not be appropriate for designing wind turbine foundations. To date, the majority of offshore wind turbines are supported by large diameter monopiles. These foundations are sensitive to scour which can reduce their ultimate capacity and alter their dynamic response. In this paper, the use of a vibration-based method to monitor scour is investigated. The effect of scour on the natural frequency of a model monopile was measured in a scale model test. A spring–beam finite element numerical model was developed to examine the foundation response. The model, which used springs tuned to the small-strain stiffness of the sand, was shown to be capable of capturing the change in frequency observed in the scale test. This numerical procedure was extended to investigate the response of a full-scale wind turbine over a range of soil densities, which might be experienced at offshore development sites. Results suggest that wind turbines founded in loose sand would exhibit the largest relative reductions in natural frequency resulting from scour

Corotating light cylinders and Alfv\'en waves

Exact relativistic force free fields with cylindrical symmetry are explored. Such fields are generated in the interstellar gas via their connection to pulsar magnetospheres both inside and outside their light cylinders. The possibility of much enhanced interstellar fields wound on cylinders of Solar system dimensions is discussed but these are most likely unstable.Comment: 6 pages, 6 figures, accepted by MNRA

Synthesis of Polycyclic Aromatic Hydrocarbons by Phenyl Addition-Dehydrocyclization: The Third Way.

Polycyclic aromatic hydrocarbons (PAHs) represent the link between resonance-stabilized free radicals and carbonaceous nanoparticles generated in incomplete combustion processes and in circumstellar envelopes of carbon rich asymptotic giant branch (AGB) stars. Although these PAHs resemble building blocks of complex carbonaceous nanostructures, their fundamental formation mechanisms have remained elusive. By exploring these reaction mechanisms of the phenyl radical with biphenyl/naphthalene theoretically and experimentally, we provide compelling evidence on a novel phenyl-addition/dehydrocyclization (PAC) pathway leading to prototype PAHs: triphenylene and fluoranthene. PAC operates efficiently at high temperatures leading through rapid molecular mass growth processes to complex aromatic structures, which are difficult to synthesize by traditional pathways such as hydrogen-abstraction/acetylene-addition. The elucidation of the fundamental reactions leading to PAHs is necessary to facilitate an understanding of the origin and evolution of the molecular universe and of carbon in our galaxy