Terahertz Waveguiding in Silicon-Core Fibers

We propose the use of a silicon-core optical fiber for terahertz (THz) waveguide applications. Finite-difference time-domain simulations have been performed based on a cylindrical waveguide with a silicon core and silica cladding. High-resistivity silicon has a flat dispersion over a 0.1 - 3 THz range, making it viable for propagation of tunable narrowband CW THz and possibly broadband picosecond pules of THz radiation. Simulations show the propagation dynamics and the integrated intensity, from which transverse mode profiles and absorption lengths are extraced. It is found that for 140 - 250 micron core diameters the mode is primarily confined to the core, such that the overall absorbance is only slightly less than in bulk polycrystalline silicon.Comment: 6 pages, 3 figures, journal submissio

FeH Absorption in the Near-Infrared Spectra of Late M and L Dwarfs

We present medium-resolution z-, J-, and H-band spectra of four late-type dwarfs with spectral types ranging from M8 to L7.5. In an attempt to determine the origin of numerous weak absorption features throughout their near-infrared spectra, and motivated by the recent tentative identification of the E 4\Pi- A ^4\Pi system of FeH near 1.6 microns in umbral and cool star spectra, we have compared the dwarf spectra to a laboratory FeH emission spectrum. We have identified nearly 100 FeH absorption features in the z-, J-, and H-band spectra of the dwarfs. In particular, we have identified 34 features which dominate the appearance of the H-band spectra of the dwarfs and which appear in the laboratory FeH spectrum. Finally, all of the features are either weaker or absent in the spectrum of the L7.5 dwarf which is consistent with the weakening of the known FeH bandheads in the spectra of the latest L dwarfs.Comment: accepted by Ap

A Method of Correcting Near-Infrared Spectra for Telluric Absorption

We present a method for correcting near-infrared medium-resolution spectra for telluric absorption. The method makes use of a spectrum of an A0V star, observed near in time and close in airmass to the target object, and a high-resolution model of Vega, to construct a telluric correction spectrum that is free of stellar absorption features. The technique was designed specifically to perform telluric corrections on spectra obtained with SpeX, a 0.8-5.5 micron, medium-resolution cross-dispersed spectrograph at the NASA Infrared Telescope Facility, and uses the fact that for medium resolutions there exist spectral regions uncontaminated by atmospheric absorption lines. However, it is also applicable (in a somewhat modified form) to spectra obtained with other near-infrared spectrographs. An IDL-based code that carries out the procedures is available for downloading via the World Wide Web from the IRTF website.Comment: 39 pages, 10 figures, To appear in the Feb 2003 issue of PASP; IDL source code, as well as full resolution versions of the figures, are available at http://irtfweb.ifa.hawaii.edu/Facility/spex

Marshall University Music Department Presents a Tuba & Euphonium Day 2014, Featuring Velvet Brown

https://mds.marshall.edu/music_perf/1285/thumbnail.jp

Dediščina izjemnih osebnosti kot potencial za razvoj kulturnega turizma v Romuniji

This article investigates how domestic tourists perceive the possibilities of boosting cultural heritage tourism in Romania, through the capitalization of national genius personalities. The methodology is based on the survey method. The research identified 22 geniuses, largely represented in national culture, and acknowledged and demanded by the market. The vast majority have been converted into tourist attractions, however those of international visibility are missing or are underrepresented in Romanian heritage tourism. An increased focus on geniuses would be highly valued by tourists and could reinforce the value of cultural heritage, consequently, boosting tourism resources. This would lead to multiple and sustainable benefits for destinations’ development, but certain infrastructure and management gaps would need to be filled.Avtorji v članku proučujejo mnenja domačih turistov o možnostih spodbujanja razvoja kulturnega turizma v Romuniji na podlagi izjemnih osebnosti iz romunske kulturne zgodovine. Uporabljena metodologija temelji na anketi, v kateri so vprašani izpostavili 22 romunskih kulturnih osebnosti, prepoznanih na trgu. Večina je bila preobražena v turistične zanimivosti, pri čemer pa v romunskem dediščinskem turizmu manjkajo mednarodno prepoznavne osebnosti ali so te slabo zastopane. Večji poudarek na tovrstnih osebnostih bi turisti zelo dobro sprejeli, hkrati bi se s tem povečala vrednost kulturne dediščine, kar bi posledično spodbudilo razvoj novih turističnih virov. Navedeno bi imelo različne trajnostne koristi za razvoj destinacij, treba pa bi bilo zapolniti nekatere vrzeli v infrastrukturi in upravljanju

Discoveries from a Near-infrared Proper Motion Survey using Multi-epoch 2MASS Data

We have conducted a 4030-square-deg near-infrared proper motion survey using multi-epoch data from the Two Micron All-Sky Survey (2MASS). We find 2778 proper motion candidates, 647 of which are not listed in SIMBAD. After comparison to DSS images, we find that 107 of our proper motion candidates lack counterparts at B-, R-, and I-bands and are thus 2MASS-only detections. We present results of spectroscopic follow-up of 188 targets that include the infrared-only sources along with selected optical-counterpart sources with faint reduced proper motions or interesting colors. We also establish a set of near-infrared spectroscopic standards with which to anchor near-infrared classifications for our objects. Among the discoveries are six young field brown dwarfs, five "red L" dwarfs, three L-type subdwarfs, twelve M-type subdwarfs, eight "blue L" dwarfs, and several T dwarfs. We further refine the definitions of these exotic classes to aid future identification of similar objects. We examine their kinematics and find that both the "blue L" and "red L" dwarfs appear to be drawn from a relatively old population. This survey provides a glimpse of the kinds of research that will be possible through time-domain infrared projects such as the UKIDSS Large Area Survey, various VISTA surveys, and WISE, and also through z- or y-band enabled, multi-epoch surveys such as Pan-STARRS and LSST.Comment: To appear in the September 2010 issue of The Astrophysical Journal, Supplement Serie

Clouds in the Coldest Brown Dwarfs: FIRE Spectroscopy of Ross 458C

Condensate clouds are a salient feature of L dwarf atmospheres, but have been assumed to play little role in shaping the spectra of the coldest T-type brown dwarfs. Here we report evidence of condensate opacity in the near-infrared spectrum of the brown dwarf candidate Ross 458C, obtained with the Folded-Port Infrared Echellette (FIRE) spectrograph at the Magellan Telescopes. These data verify the low-temperature nature of this source, indicating a T8 spectral classification, log Lbol/Lsun = -5.62+/-0.03, Teff = 650+/-25 K, and a mass at or below the deuterium burning limit. The data also reveal enhanced emission at K-band associated with youth (low surface gravity) and supersolar metallicity, reflecting the properties of the Ross 458 system (age = 150-800 Myr, [Fe/H] = +0.2 to +0.3). We present fits of FIRE data for Ross 458C, the T9 dwarf ULAS J133553.45+113005.2, and the blue T7.5 dwarf SDSS J141624.08+134826.7B, to cloudless and cloudy spectral models from Saumon & Marley. For Ross 458C we confirm a low surface gravity and supersolar metallicity, while the temperature differs depending on the presence (635 [+25,-35] K) or absence (760 [+70,-45] K) of cloud extinction. ULAS J1335+1130 and SDSS J1416+1348B have similar temperatures (595 [+25,-45] K), but distinct surface gravities (log g = 4.0-4.5 cgs versus 5.0-5.5 cgs) and metallicities ([M/H] ~ +0.2 versus -0.2). In all three cases, cloudy models provide better fits to the spectral data, significantly so for Ross 458C. These results indicate that clouds are an important opacity source in the spectra of young cold T dwarfs, and should be considered when characterizing the spectra of planetary-mass objects in young clusters and directly-imaged exoplanets. The characteristics of Ross 458C suggest it could itself be regarded as a planet, albeit one whose cosmogony does not conform with current planet formation theories.Comment: Accepted for publication to ApJ: 18 pages, 11 figures in emulateapj forma