Central Appalachian Understory Red Spruce (Picea rubens Sarg.) Growth Rates and Allometric Relationships

Red spruce (Picea rubens) was a prized timber species in West Virginia during the era of resource exploitation in the late 1800s and early 1900s. Consequently, Central Appalachian red spruce has faced large reductions in range and changes in stand composition. This region is relatively underrepresented in literature partially due to these constrictions. Investigating how stem growth occurs in young individuals can fill in some of our gaps in understanding the species and aid in restoration efforts. We sampled an array of high elevation sites on federal and state lands in West Virginia to analyze understory spruce growth and allometric relationships. We compared these relationships to those found in other regions in the range of red spruce. Stem analysis was carried out on understory trees. Results were applied to build reference curves to model growth percentiles for the young trees. Growth rates tend to peak between 10 and 30 years of age. Heights range from 0.95 m to 6.85 m after 50 years. Results allow for comparison of growth rates to the cohort of understory red spruce regionally. Nonlinear analysis was carried out on allometric measures on the same cohort of red spruce. Diameter at breast height was found to be a somewhat reliable predictor of total height as well as crown width. Total height was less reliable when predicting crown width. None of the three measures were found to be reliable for predicting tree age as may be expected with a shade tolerant species

Toward tactilely transparent gloves: Collocated slip sensing and vibrotactile actuation

Tactile information plays a critical role in the human ability to manipulate objects with one\u27s hands. Many environments require the use of protective gloves that diminish essential tactile feedback. Under these circumstances, seemingly simple tasks such as picking up an object can become very difficult. This paper introduces the SlipGlove, a novel device that uses an advanced sensing and actuation system to return this vital tactile information to the user. Our SlipGlove prototypes focus on providing tactile cues associated with slip between the glove and a contact surface. Relative motion is sensed using optical mouse sensors embedded in the glove\u27s surface. This information is conveyed to the wearer via miniature vibration motors placed inside the glove against the wearer\u27s skin. The collocation of slip sensing and tactile feedback creates a system that is natural and intuitive to use. We report results from a human subject study demonstrating that the SlipGlove allows the wearer to approach the capabilities of bare skin in detecting and reacting to fingertip slip. Users of the SlipGlove also had significantly faster and more consistent reaction to fingertip slip when compared to a traditional glove design. The SlipGlove technology allows us to enhance human perception when interacting with real environments and move toward the goal of a tactilely transparent glove

A Blind Search for Magnetospheric Emissions from Planetary Companions to Nearby Solar-type Stars

This paper reports a blind search for magnetospheric emissions from planets around nearby stars. Young stars are likely to have much stronger stellar winds than the Sun, and because planetary magnetospheric emissions are powered by stellar winds, stronger stellar winds may enhance the radio luminosity of any orbiting planets. Using various stellar catalogs, we selected nearby stars (<~ 30 pc) with relatively young age estimates (< 3 Gyr). We constructed different samples from the stellar catalogs, finding between 100 and several hundred stars. We stacked images from the 74-MHz (4-m wavelength) VLA Low-frequency Sky Survey (VLSS), obtaining 3\sigma limits on planetary emission in the stacked images of between 10 and 33 mJy. These flux density limits correspond to average planetary luminosities less than 5--10 x 10^{23} erg/s. Using recent models for the scaling of stellar wind velocity, density, and magnetic field with stellar age, we estimate scaling factors for the strength of stellar winds, relative to the Sun, in our samples. The typical kinetic energy carried by the stellar winds in our samples is 15--50 times larger than that of the Sun, and the typical magnetic energy is 5--10 times larger. If we assume that every star is orbited by a Jupiter-like planet with a luminosity larger than that of the Jovian decametric radiation by the above factors, our limits on planetary luminosities from the stacking analysis are likely to be a factor of 10--100 above what would be required to detect the planets in a statistical sense. Similar statistical analyses with observations by future instruments, such as the Low Frequency Array (LOFAR) and the Long Wavelength Array (LWA), offer the promise of improvements by factors of 10--100.Comment: 11 pages; AASTeX; accepted for publication in A

Probing the Space of Toric Quiver Theories

We demonstrate a practical and efficient method for generating toric Calabi-Yau quiver theories, applicable to both D3 and M2 brane world-volume physics. A new analytic method is presented at low order parametres and an algorithm for the general case is developed which has polynomial complexity in the number of edges in the quiver. Using this algorithm, carefully implemented, we classify the quiver diagram and assign possible superpotentials for various small values of the number of edges and nodes. We examine some preliminary statistics on this space of toric quiver theories

Towards Space-like Photometric Precision from the Ground with Beam-Shaping Diffusers

We demonstrate a path to hitherto unachievable differential photometric precisions from the ground, both in the optical and near-infrared (NIR), using custom-fabricated beam-shaping diffusers produced using specialized nanofabrication techniques. Such diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. This PSF reshaping significantly increases the achievable dynamic range of our observations, increasing our observing efficiency and thus better averages over scintillation. Diffusers work in both collimated and converging beams. We present diffuser-assisted optical observations demonstrating $62^{+26}_{-16}$ppm precision in 30 minute bins on a nearby bright star 16-Cygni A (V=5.95) using the ARC 3.5m telescope---within a factor of $\sim$2 of Kepler's photometric precision on the same star. We also show a transit of WASP-85-Ab (V=11.2) and TRES-3b (V=12.4), where the residuals bin down to $180^{+66}_{-41}$ppm in 30 minute bins for WASP-85-Ab---a factor of $\sim$4 of the precision achieved by the K2 mission on this target---and to 101ppm for TRES-3b. In the NIR, where diffusers may provide even more significant improvements over the current state of the art, our preliminary tests have demonstrated $137^{+64}_{-36}$ppm precision for a $K_S =10.8$ star on the 200" Hale Telescope. These photometric precisions match or surpass the expected photometric precisions of TESS for the same magnitude range. This technology is inexpensive, scalable, easily adaptable, and can have an important and immediate impact on the observations of transits and secondary eclipses of exoplanets.Comment: Accepted for publication in ApJ. 30 pages, 20 figure

Hyperstrong Radio-Wave Scattering in the Galactic Center. II. A Likelihood Analysis of Free Electrons in the Galactic Center

The scattering diameters of Sgr A* and several nearby OH masers (~ 1" at 1 GHz) indicate that a region of enhanced scattering is along the line of sight to the Galactic center. We combine radio-wave scattering data and free-free emission and absorption measurements in a likelihood analysis that constrains the following parameters of the GC scattering region: The GC-scattering region separation, d; the angular extent of the region, \psi_l; the outer scale on which density fluctuations occur, l_0; and the gas temperature, T. The maximum likelihood estimates of these parameters are d = 133_{-80}^{+200} pc, 0.5 degrees <= \psi_l <~ 1 degrees, and (l_0/1 pc)^{2/3}T^{-1/2} = 10^{-7 +/- 0.8}. As host media for the scattering, we consider the photoionized surface layers of molecular clouds and the interfaces between molecular clouds and the 10^7 K ambient gas. We are unable to make an unambiguous determination, but we favor an interface model in which the scattering medium is hot (T ~ 10^6 K) and dense (n_e ~ 10 cm^{-3}). The GC scattering region produces a 1 GHz scattering diameter for an extragalactic source of 90", if the region is a single screen, or 180", if the region wraps around the GC, as appears probable. We modify the Taylor-Cordes model for the Galactic distribution of free electrons in order to include an explicit GC component. Pulsars seen through this region will have a dispersion measure of approximately 2000 pc cm^{-3}, of which 75% arises from the GC component. We stress the uniqueness of the GC scattering region, probably resulting from the high-pressure environment in the GC.Comment: 39 pages with 9 PostScript figures; LaTeX2e with AASTeX macro aaspp4, to be published in Ap

Pennsylvania Folklife Vol. 19, No. 2

• Powwowing in Berks County • Belsnickling in Paxtonville • The Folk Tradition of the Sweetheart Tree • Pigpens and Piglore in Rural Pennsylvania • Gravestones and Ostentation: A Study of Five Delaware County Cemeteries • Notes on Eighteenth-Century Emigration to the British Colonies • A Siegerland Emigrant List of 1738 • Local Place Names: Folk-Cultural Questionnaire No. 14https://digitalcommons.ursinus.edu/pafolklifemag/1038/thumbnail.jp

G359.87+0.18: An FR II Radio Galaxy 15 Arcminutes from Sgr A*. Implications for the Scattering Region in the Galactic Center

G359.87+0.18 is an enigmatic object located 15' from Sgr A*. It has been variously classified as an extragalactic source, Galactic jet source, and young supernova remnant. We present new observations of G359.87+0.18 between 0.33 and 15 GHz and use these to argue that this source is an Faranoff-Riley II radio galaxy. We are able to place a crude limit on its redshift of z > 0.1. The source has a spectral index \alpha < -1 (S \propto \nu^\alpha), suggestive of a radio galaxy with a redshift z >~ 2. The scattering diameters of Sgr A* and several nearby OH masers (~ 1" at 1 GHz) indicate that a region of enhanced scattering is along the line of sight to the Galactic center. If the region covers the Galactic center uniformly, the implied diameter for a background source is at least 600" at 0.33 GHz, in contrast with the observed 20" diameter of G359.87+0.18. Using the scattering diameter of a nearby OH maser OH 359.762+0.120 and the widths of two, nearby, non-thermal threads, G0.08+0.15 and G359.79+0.17, we show that a uniform scattering region should cover G359.87+0.18. We therefore conclude that the Galactic center scattering region is inhomogeneous on a scale of 5' (~ 10 pc at a distance of 8.5 kpc). This scale is comparable to the size scale of molecular clouds in the Galactic center. The close agreement between these two lengths scales is an indication that the scattering region is linked intimately to the Galactic center molecular clouds.Comment: Accepted for publication in the ApJ, vol. 515, LaTeX2e manuscript using aaspp4 macro, 19 pages, 8 figures in 11 PostScript file