The Occurrence of Chestnut Lamprey (lchthyomyzon castaneus; Pisces: Petromyzontidae) in the Chariton River in South-Central Iowa

In the mid-1990s, Iowa Department of Natural Resources (IDNR) Fisheries Bureau biologists began receiving reports from anglers of a parasitic lamprey attached to fish taken immediately downstream from Rathbun Lake on the Chariton River in south-central Iowa; these reports have continued to present. In 2002, the IDNR received and identified a chestnut lamprey (Ichthyomyzon castaneus Girard) from an angler who removed the lamprey from a common carp (Cyprinus carpio Linnaeus) he captured. This record was the first for a lamprey from the Chariton River drainage in Iowa. Five additional specimens of chestnut lamprey have been collected and identified since this specimen was found, all from the same location. The Rathbun Lake tailrace is one of only a few locations on Iowa\u27s interior rivers and streams with verified records for chestnut lamprey

Preheated Advection Dominated Accretion Flow

All high temperature accretion solutions including ADAF are physically thick, so outgoing radiation interacts with the incoming flow, sharing as much or more resemblance with classical spherical accretion flows as with disk flows. We examine this interaction for the popular ADAF case. We find that without allowance for Compton preheating, a very restricted domain of ADAF solution is permitted and with Compton preheating included a new high temperature PADAF branch appears in the solution space. In the absence of preheating, high temperature flows do not exist when the mass accretion rate mdot == Mdot c^2 / L_E >~ 10^-1.5. Below this mass accretion rate, a roughly conical region around the hole cannot sustain high temperature ions and electrons for all flows having mdot >~ 10^-4, which may lead to a funnel possibly filled with a tenuous hot outgoing wind. If the flow starts at large radii with the usual equilibrium temperature ~10^4 K, the critical mass accretion rate is much lower, mdot \~10^-3.7 above which level no self-consistent ADAF (without preheating) can exist. However, above this critical mass accretion rate, the flow can be self-consistently maintained at high temperature if Compton preheating is considered. These solutions constitute a new branch of solutions as in spherical accretion flows. High temperature PADAF flows can exist above the critical mass accretion rate in addition to the usual cold thin disk solutions. We also find solutions where the flow near the equatorial plane accretes normally while the flow near the pole is overheated by Compton preheating, possibly becoming, a polar wind, solutions which we designate WADAF.Comment: 41 pages with 10 postscript figures (aastex5). Submitted to Ap

Does the Slim-Disk Model Correctly Consider Photon-Trapping Effects?

We investigate the photon-trapping effects in the super-critical black hole accretion flows by solving radiation transfer as well as the energy equations of radiation and gas. It is found that the slim-disk model generally overestimates the luminosity of the disk at around the Eddington luminosity (L_E) and is not accurate in describing the effective temperature profile, since it neglects time delay between energy generation at deeper inside the disk and energy release at the surface. Especially, the photon-trapping effects are appreciable even below L ~ L_E, while they appear above ~ 3L_E according to the slim disk. Through the photon-trapping effects, the luminosity is reduced and the effective temperature profile becomes flatter than r^{-3/4} as in the standard disk. In the case that the viscous heating is effective only around the equatorial plane, the luminosity is kept around the Eddington luminosity even at very large mass accretion rate, Mdot>>L_E/c^2. The effective temperature profile is almost flat, and the maximum temperature decreases in accordance with rise in the mass accretion rate. Thus, the most luminous radius shifts to the outer region when Mdot/(L_E/c^2) >> 10^2. In the case that the energy is dissipated equally at any heights, the resultant luminosity is somewhat larger than in the former case, but the energy-conversion efficiency still decreases with increase of the mass accretion rate, as well. The most luminous radius stays around the inner edge of the disk in the latter case. Hence, the effective temperature profile is sensitive to the vertical distribution of energy production rates, so is the spectral shape. Future observations of high L/L_E objects will be able to test our model.Comment: 10 pages, 7 figures, accepted for publication in Ap

Spin correlations in p⃗p⃗→pnπ+\vec{p}\vec{p}\to pn\pi^{+} pion production near threshold

A first measurement of longitudinal as well as transverse spin correlation coefficients for the reaction $\vec{p}\vec{p}\to pn\pi^+$ was made using a polarized proton target and a polarized proton beam. We report kinematically complete measurements for this reaction at 325, 350, 375 and 400 MeV beam energy. The spin correlation coefficients $A_{xx}+A_{yy}, A_{xx}-A_{yy}, A_{zz}, A_{xz},$ and the analyzing power $A_{y},$ as well as angular distributions for $\sigma(\theta_{\pi})$ and the polarization observables $A_{ij}(\theta_{\pi})$ were extracted. Partial wave cross sections for dominant transition channels were obtained from a partial wave analysis that included the transitions with final state angular momenta of $l\leq 1$. The measurements of the ${\vec{p}\vec{p}\to pn\pi^{+}}$ polarization observables are compared with the predictions from the J\"ulich meson exchange model. The agreement is very good at 325 MeV, but it deteriorates increasingly for the higher energies. At all energies agreement with the model is better than for the reaction ${\vec{p}\vec{p}\to pp\pi^{0}}$.Comment: Preprint, 21 pp, submitted to Phys. Rev. C. Keywords: Mesons, Polarization, Spin Correlations, Few body system

Volumetric imaging of shark tail hydrodynamics reveals a three-dimensional dual-ring vortex wake structure

Understanding how moving organisms generate locomotor forces is fundamental to the analysis of aerodynamic and hydrodynamic flow patterns that are generated during body and appendage oscillation. In the past, this has been accomplished using two-dimensional planar techniques that require reconstruction of three-dimensional flow patterns. We have applied a new, fully three-dimensional, volumetric imaging technique that allows instantaneous capture of wake flow patterns, to a classic problem in functional vertebrate biology: the function of the asymmetrical (heterocercal) tail of swimming sharks to capture the vorticity field within the volume swept by the tail. These data were used to test a previous three-dimensional reconstruction of the shark vortex wake estimated from two-dimensional flow analyses, and show that the volumetric approach reveals a different vortex wake not previously reconstructed from two-dimensional slices. The hydrodynamic wake consists of one set of dual-linked vortex rings produced per half tail beat. In addition, we use a simple passive shark-tail model under robotic control to show that the three-dimensional wake flows of the robotic tail differ from the active tail motion of a live shark, suggesting that active control of kinematics and tail stiffness plays a substantial role in the production of wake vortical patterns

Analyzing Powers for pp → pnπ^+

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Dependence of pp->pp pi0 near Threshold on the Spin of the Colliding Nucleons

A polarized internal atomic hydrogen target and a stored, polarized beam are used to measure the spin-dependent total cross section Delta_sigma_T/sigma_tot, as well as the polar integrals of the spin correlation coefficient combination A_xx-A_yy, and the analyzing power A_y for pp-> pp pi0 at four bombarding energies between 325 and 400 MeV. This experiment is made possible by the use of a cooled beam in a storage ring. The polarization observables are used to study the contribution from individual partial waves.Comment: 6 pages, 1 table, 4 figures, corrected equations 2 and

Observation of strong final-state effects in pi+ production in pp collisions at 400 MeV

Differential cross sections of the reactions $pp \to d\pi^+$ and $pp \to pn\pi^+$ have been measured at $T_p = 400$ MeV by detecting the charged ejectiles in the angular range $4^0 \leq \Theta_{Lab} \leq 21^\circ$. The deduced total cross sections agree well with those published previously for neighbouring energies. The invariant mass spectra are observed to be strongly affected by $\Delta$ production and $NN$ final-state interaction. The data are well described by Monte Carlo simulations including both these effects. The ratio of $pp \to pn\pi^+$ and $pp \to d\pi^+$ cross sections also compares favourably to a recent theoretical prediction which suggests a dominance of $np$-production in the relative $^3S_1$-state.Comment: 17 pages, 5 figure

Elastic modulus of tree frog adhesive toe pads

Previous work using an atomic force microscope in nanoindenter mode indicated that the outer, 10- to 15-μm thick, keratinised layer of tree frog toe pads has a modulus of elasticity equivalent to silicone rubber (5–15 MPa) (Scholz et al. 2009), but gave no information on the physical properties of deeper structures. In this study, micro-indentation is used to measure the stiffness of whole toe pads of the tree frog, Litoria caerulea. We show here that tree frog toe pads are amongst the softest of biological structures (effective elastic modulus 4–25 kPa), and that they exhibit a gradient of stiffness, being stiffest on the outside. This stiffness gradient results from the presence of a dense network of capillaries lying beneath the pad epidermis, which probably has a shock absorbing function. Additionally, we compare the physical properties (elastic modulus, work of adhesion, pull-off force) of the toe pads of immature and adult frogs