Ectopic Sequestered Thyroid Tissue: An Unusual Cause of a Mediastinal Mass

An 80-year-old female presented with an incidental finding of a retrosternal mass on magnetic resonance imaging. Ultrasound demonstrated a mediastinal lesion adjacent to but separate from the inferior pole of the right thyroid lobe. Fine needle aspiration cytology demonstrated colloid and follicular cells. At surgery, the right thyroid lobe was found to be normal. A discrete 5 cm nodule was found in the anterior mediastinum separate from the thyroid and just anterior and to the right of the trachea and thymus. The nodule had a vascular pedicle arising from the mediastinum. The differential diagnosis included metastatic thyroid carcinoma. Histology was consistent with a benign ectopic sequestered thyroid nodule. Extensive investigations demonstrated no sign of a thyroid malignancy

Dynamics of Learning with Restricted Training Sets I: General Theory

We study the dynamics of supervised learning in layered neural networks, in the regime where the size $p$ of the training set is proportional to the number $N$ of inputs. Here the local fields are no longer described by Gaussian probability distributions and the learning dynamics is of a spin-glass nature, with the composition of the training set playing the role of quenched disorder. We show how dynamical replica theory can be used to predict the evolution of macroscopic observables, including the two relevant performance measures (training error and generalization error), incorporating the old formalism developed for complete training sets in the limit $\alpha=p/N\to\infty$ as a special case. For simplicity we restrict ourselves in this paper to single-layer networks and realizable tasks.Comment: 39 pages, LaTe

Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. I. NGC 6940

We present near-infrared spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. High-resolution (R$\simeq$45000) and high signal-to-noise ratio (S/N > 100) near-infrared H and K band spectra were gathered with the Immersion Grating Infrared Spectrograph (IGRINS) on the 2.7m Smith Telescope at McDonald Observatory. We obtained abundances of H-burning (C, N, O), ${\alpha}$ (Mg, Si, S, Ca), light odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Fe, Co, Ni) and neutron-capture (Ce, Nd, Yb) elements. We report the abundances of S, P, K, Ce, and Yb in NGC 6940 for the first time. Many OH and CN features in the H band were used to obtain O and N abundances. C abundances were measured from four different features: CO molecular lines in the K band, high excitation C I lines present in both near-infrared and optical, CH and $C_2$ bands in the optical region. We have also determined $^{12}C/^{13}C$ ratios from the R-branch band heads of first overtone (2-0) and (3-1) $^{12}CO$ (2-0) $^{13}CO$ lines near 23440 \overset{\lower.5em\circ}{\mathrm{A}} and (3-1) $^{13}CO$ lines at about 23730 \overset{\lower.5em\circ}{\mathrm{A}}. We have also investigated the HF feature at 23358.3 \overset{\lower.5em\circ}{\mathrm{A}}, finding solar fluorine abundances without ruling out a slight enhancement. For some elements (such as the ${\alpha}$ group), IGRINS data yield more internally self-consistent abundances. We also revisited the CMD of NGC 6940 by determining the most probable cluster members using Gaia DR2. Finally, we applied Victoria isochrones and MESA models in order to refine our estimates of the evolutionary stages of our targets.Comment: 16 pages, 10 figure

Heavy rain effects on airplane performance

The objective is to determine if the aerodynamic characteristics of an airplane are altered while flying in the rain. Wind-tunnel tests conducted at the NASA Langley Research Center (LaRC) have shown losses in maximum lift, reduction in stall angle, and increases in drag when a wing is placed in a simulated rain spray. For these tests the water spray concentration used represented a very heavy rainfall. A lack of definition of the scaling laws for aerodynamic testing in a two-phase, two-component flow makes interpolation of the wind-tunnel test uncertain. Tests of a large-scale wing are to be conducted at the LaRC. The large-scale wing is mounted on top of the Aircraft Landing Dynamics Facility (ALDF) carriage. This carriage (which is 70-foot long, 30-foot wide, and 30-foot high) is propelled with the wing model attached down a 3000-foot long test track by a water jet at speeds of up to 170 knots. A simulated rain spray system has been installed along 500 feet of the test track and can simulate rain falls from 2 to 40 inches/hour. Operational checks are underway and the initial tests should be completed by the Fall of 1989

Detection of Coulomb Charging around an Antidot in the Quantum Hall Regime

We have detected oscillations of the charge around a potential hill (antidot) in a two-dimensional electron gas as a function of a large magnetic field B. The field confines electrons around the antidot in closed orbits, the areas of which are quantised through the Aharonov-Bohm effect. Increasing B reduces each state's area, pushing electrons closer to the centre, until enough charge builds up for an electron to tunnel out. This is a new form of the Coulomb blockade seen in electrostatically confined dots. Addition and excitation spectra in DC bias confirm the Coulomb blockade of tunnelling.Comment: 4 pages, 4 Postscript figure

Magnetic moment non-conservation in magnetohydrodynamic turbulence models

The fundamental assumptions of the adiabatic theory do not apply in presence of sharp field gradients as well as in presence of well developed magnetohydrodynamic turbulence. For this reason in such conditions the magnetic moment $\mu$ is no longer expected to be constant. This can influence particle acceleration and have considerable implications in many astrophysical problems. Starting with the resonant interaction between ions and a single parallel propagating electromagnetic wave, we derive expressions for the magnetic moment trapping width $\Delta \mu$ (defined as the half peak-to-peak difference in the particle magnetic moment) and the bounce frequency $\omega_b$. We perform test-particle simulations to investigate magnetic moment behavior when resonances overlapping occurs and during the interaction of a ring-beam particle distribution with a broad-band slab spectrum. We find that magnetic moment dynamics is strictly related to pitch angle $\alpha$ for a low level of magnetic fluctuation, $\delta B/B_0 = (10^{-3}, \, 10^{-2})$, where $B_0$ is the constant and uniform background magnetic field. Stochasticity arises for intermediate fluctuation values and its effect on pitch angle is the isotropization of the distribution function $f(\alpha)$. This is a transient regime during which magnetic moment distribution $f(\mu)$ exhibits a characteristic one-sided long tail and starts to be influenced by the onset of spatial parallel diffusion, i.e., the variance $$ grows linearly in time as in normal diffusion. With strong fluctuations $f(\alpha)$ isotropizes completely, spatial diffusion sets in and $f(\mu)$ behavior is closely related to the sampling of the varying magnetic field associated with that spatial diffusion.Comment: 13 pages, 10 figures, submitted to PR

Water as a Factor in Energy Resources Development

Water, in many cases, is a key factor in the development of energy resources in the western states. The total water supply available in the arid west is fixed; yet potential water uses in the region are growing continually. In fact, in many areas quantities of water desired to be put to beneficial use has already surpassed the limit of local supplies as indicated by filings for water rights. The availability of water, in adequate quantities and of suitable quality, is one of the essentials to the economic viability of some economic sectors in the states in the Colorado River Basin. Many existing water uses are already under economic pressure which could shift water to users who can afford to pay higher prices. With the entire region undergoing an energy boom, Duchesne and Uintah Counties, which are agriculture oriented, for example, may see water bought from agriculture for energy development