The morphology-density relation for dwarf galaxies

The morphology-density relation is examined for dwarf galaxies with absolute magnitudes -18 less than or equal to M sub B sub T less than or equal to -12.5, based on a deep photographic survey of nearby groups and clusters of galaxies. Results are given. Compared to dwarf ellipticals, dwarf irregulars form a more extended population in nearby clusters, and may in fact be entirely absent from the cluster cores. The spatial distribution of dwarf ellipticals in clusters depends on luminosity and the presence or absence of nucleation. Nucleated dE's and non-nucleated dE's fainter than M sub B sub T approx. -13.5 are concentrated toward the centers of clusters like the giant E and S0 galaxies. In contrast, non-nucleated dE's brighter than M sub B sub T approx. -14.5 are distributed like the spirals and irregulars. The intrinsic shapes of the bright non-nucleated dE's are similar to those of the dwarf irregulars, suggesting a possible evolutionary connection between these two classes of galaxies

Inference of the drivers of collective movement in two cell types: Dictyostelium and melanoma

Collective cell movement is a key component of many important biological processes, including wound healing, the immune response and the spread of cancers. To understand and influence these movements, we need to be able to identify and quantify the contribution of their different underlying mechanisms. Here, we define a set of six candidate models—formulated as advection–diffusion–reaction partial differential equations—that incorporate a range of cell movement drivers. We fitted these models to movement assay data from two different cell types: Dictyostelium discoideum and human melanoma. Model comparison using widely applicable information criterion suggested that movement in both of our study systems was driven primarily by a self-generated gradient in the concentration of a depletable chemical in the cells' environment. For melanoma, there was also evidence that overcrowding influenced movement. These applications of model inference to determine the most likely drivers of cell movement indicate that such statistical techniques have potential to support targeted experimental work in increasing our understanding of collective cell movement in a range of systems

The Behavior of Soluble Salt in Sharkey Clay

Soluble salt problems do exist and are significant in Arkansas. Studies have been conducted on Crowley silt loam (Typic Albaqualfs) which have established the behavior of soluble salt in that soil. The major objective of this study was to quantify the behavior of soluble salt in a second important Mississippi River Delta soil - the Sharkey (Vertic Haplaquepts). To this end, estimation of the downward redistribution of salt and the estimation of various components of the water balance for this soil served as specific objectives. Field studies were designed to monitor the movement of salt in the Sharkey soil and to characterize selected components of the water balance. In total, three tentative conclusions may be drawn from the data. First, the infiltration for the Sharkey soil was approximately three times that of the Crowley silt loam. The average value was 29 cm for the rice season. Second, levee seepage, while significant for small plots, was shown to be small for production-sized fields. Levee seepage remained relatively constant throughout the season and averaged 0.025 nvfym/d. And third, downward redistribution of salt was large and appeared to follow a pattern where a peak occurred at the surface and, possibly, at the lower soil depths

Microsecond resolution of quasiparticle tunneling in the single-Cooper-pair-transistor

We present radio-frequency measurements on a single-Cooper-pair-transistor in which individual quasiparticle poisoning events were observed with microsecond temporal resolution. Thermal activation of the quasiparticle dynamics is investigated, and consequently, we are able to determine energetics of the poisoning and un-poisoning processes. In particular, we are able to assign an effective quasiparticle temperature to parameterize the poisoning rate.Comment: 4 pages, 4 fig

Electrically detected magnetic resonance using radio-frequency reflectometry

The authors demonstrate readout of electrically detected magnetic resonance at radio frequencies by means of an LCR tank circuit. Applied to a silicon field-effect transistor at milli-kelvin temperatures, this method shows a 25-fold increased signal-to-noise ratio of the conduction band electron spin resonance and a higher operational bandwidth of > 300 kHz compared to the kHz bandwidth of conventional readout techniques. This increase in temporal resolution provides a method for future direct observations of spin dynamics in the electrical device characteristics.Comment: 9 pages, 3 figure

Impulse distributions in dense granular flows: signatures of large-scale spatial structures

In this paper we report the results of simulations of a 2D gravity driven, dissipative granular flow through a hopper system. Measurements of impulse distributions P(I) on the simulated system show flow-velocity-invariant behavior of the distribution for impulses larger than the average impulse . For small impulses, however, P(I) decreases significantly with flow velocity, a phenomenon which can be attributed exclusively to collisions between grains undergoing frequent collisions. Visualizations of the system also show that these frequently colliding particles tend to form increasingly large linear clusters as the flow velocity decreases. A model is proposed for the form of P(I), given distributions of cluster size and velocity, which accurately predicts the observed form of the distribution. Thus the impulse distribution provides some insight into the formation and properties of these ``dynamic'' force chains.Comment: 4 pages, 4 figure

Lander Trajectory Reconstruction computer program

The Lander Trajectory Reconstruction (LTR) computer program is a tool for analysis of the planetary entry trajectory and atmosphere reconstruction process for a lander or probe. The program can be divided into two parts: (1) the data generator and (2) the reconstructor. The data generator provides the real environment in which the lander or probe is presumed to find itself. The reconstructor reconstructs the entry trajectory and atmosphere using sensor data generated by the data generator and a Kalman-Schmidt consider filter. A wide variety of vehicle and environmental parameters may be either solved-for or considered in the filter process