Investigating the Consistency of Stellar Evolution Models with Globular Cluster Observations via the Red Giant Branch Bump

Synthetic RGBB magnitudes are generated with the most recent theoretical stellar evolution models computed with the Dartmouth Stellar Evolution Program (DSEP) code. They are compared to the observational work of Nataf et al., who present RGBB magnitudes for 72 globular clusters. A DSEP model using a chemical composition with enhanced $\alpha$ capture [$\alpha$/Fe] $=+0.4$ and an age of 13 Gyr shows agreement with observations over metallicities ranging from [Fe/H] = $0$ to [Fe/H] $\approx-1.5$, with discrepancy emerging at lower metallicities.Comment: 11 pages, 12 figure

Systematics and distributions of the genera Cyrtusa Erichson, Ecarinosphaerula Hatch, Isoplastus Horn, Liocyrtusa Daffner, Lionothus Brown, and Zeadolopus Broun of the United States and Canada (Coleoptera: Leiodidae: Leiodinae: Leiodini)

The following genera of Leiodini (Coleoptera: Leiodidae: Leiodinae) of the continental United States and Canada are reviewed: Cyrtusa Erichson, with two species; Isoplastus Horn, with two species (one new); Liocyrtusa Daffner, with three species; Lionothus Brown, with five species (three new), and Zeadolopus Broun, with four species (all genera are in the “Cyrtusa genus group”) and Ecarinosphaerula Hatch, with one named species (in the “Leiodes genus group”). The new species are Isoplastus floridanus Peck and Cook of Florida; Lionothus bidentatus Peck and Cook of Texas and Oklahoma, Lionothus exiguus Peck and Cook of Florida and Texas, and Lionothus parvoculus Peck and Cook of Arizona and New Mexico. Bionomic data on the species are given, and complete known distributions are mapped

A revision of the species of Anogdus LeConte of the United States and Canada (Coleoptera: Leiodidae: Leiodinae: Leiodini)

A review of the genus Anogdus LeConte (Coleoptera: Leiodidae: Leiodinae: Leiodini) of North America finds 16 species. Ten of these were previously described and there are no new synonyms. Six are named as new species: A. alachua n. sp., of Florida; A. cochise, n. sp., of Arizona; A. huachuca n. sp., of Arizona; A. rileyi n. sp, of Texas; A. texanus n. sp., of Texas and Oklahoma; and A. tridens n. sp, of Arkansas, Arizona, Illinois, Indiana, Oklahoma, and Texas. A key is provided to aid identification of the species

Cold uniform spherical collapse revisited

We report results of a study of the Newtonian dynamics of N self-gravitating particles which start in a quasi-uniform spherical configuration, without initial velocities. These initial conditions would lead to a density singularity at the origin at a finite time when N \rightarrow \infty, but this singularity is regulated at any finite N (by the associated density fluctuations). While previous studies have focussed on the behaviour as a function of N of the minimal size reached during the contracting phase, we examine in particular the size and energy of the virialized halo which results. We find the unexpected result that the structure decreases in size as N increases, scaling in proportion to N^{-1/3}, a behaviour which is associated with an ejection of kinetic energy during violent relaxation which grows in proportion to N^{1/3}. This latter scaling may be qualitatively understood, and if it represents the asymptotic behaviour in N implies that this ejected energy is unbounded above. We discuss also tests we have performed which indicate that this ejection is a mean-field phenomenon (i.e. a result of collisionless dynamics).Comment: 10 pages, 9 figures; proceedings of "Invisible Universe" conference, Paris, July 200

Quasi-stationary states and the range of pair interactions

"Quasi-stationary" states are approximately time-independent out of equilibrium states which have been observed in a variety of systems of particles interacting by long-range interactions. We investigate here the conditions of their occurrence for a generic pair interaction V(r \rightarrow \infty) \sim 1/r^a with a > 0, in d>1 dimensions. We generalize analytic calculations known for gravity in d=3 to determine the scaling parametric dependences of their relaxation rates due to two body collisions, and report extensive numerical simulations testing their validity. Our results lead to the conclusion that, for a < d-1, the existence of quasi-stationary states is ensured by the large distance behavior of the interaction alone, while for a > d-1 it is conditioned on the short distance properties of the interaction, requiring the presence of a sufficiently large soft-core in the interaction potential.Comment: 5 pages, 3 figures; final version to appear in Phys. Rev. Let

The phase shift of an ultrasonic pulse at an oil layer and determination of film thickness

An ultrasonic pulse incident on a lubricating oil film in a machine element will be partially reflected and partially transmitted. The proportion of the wave amplitude reflected, termed the reflection coefficient, depends on the film thickness and the acoustic properties of the oil. When the appropriate ultrasonic frequency is used, the magnitude of the reflection coefficient can be used to determine the oil film thickness. However, the reflected wave has both a real component and an imaginary component, and both the amplitude and the phase are functions of the film thickness. The phase of the reflected wave will be shifted from that of the incident wave when it is reflected. In the present study, this phase shift is explored as the film changes and is evaluated as an alternative means to measure oil film thickness. A quas i-static theoretical model of the reflection response from an oil film has been, developed. This model relates the phase shift to the wave frequency and the film properties. Measurements of reflection coefficient from a static model oil film and also from a rotating journal bearing have been recorded. These have been used to determine the oil film thickness using both amplitude and phase shift methods. In both cases, the results agree closely with independent assessments of the oil film thickness. The model of ultrasonic reflection is further extended to incorporate mass and damping terms. Experiments show that both the mass and the internal damping of the oil films tested in this work have a negligible effect on ultrasonic reflection. A potentially v ery useful application for the simultaneous measurement of reflection coefficient amplitude and phase is that the data can be used to negate the need for a reference. The theoretical relationship between phase and amplitude is fitted to the data. An extrapolation is performed to determine the values of amplitude and phase for an infinitely thick layer. This is equivalent to the reference signal determined by measuring the reflection coefficient directly, but importantly does not require the materials to be separated. This provides a simple and effective means of continuously calibrating the film measurement approach