Floristic and Biogeographical Trends in Seaweed Assemblages from a Subtropical Insular Island Complex in the Gulf of California

Floristic and biogeographical trends of the seaweed assemblages in subtidial rocky areas were evaluated at 10 sites around Espiritu Santo Island in the Gulf of California. Seasonal sampling in two consecutive years with intensive surveys in a 500-m2 area at each site was done. An intensive search was made of previous records from the literature. We found 85 species in the field with an additional 69 species from the literature, for a total 116 species. Species composition was significantly different between sides of the island in the first year, but very similar in the second. Species composition was not influenced by the presence of epiphytes. Phenologically, most species were ephemeral or annual with a low reproductive effort. Biogeographically, tropical elements dominated, but there was an important contribution from temperate species. Our results indicate that Espiritu Santo Island is a dynamic system that is strongly influenced by local oceanographic conditions

Star Formation History and Extinction in the central kpc of M82-like Starbursts

We report on the star formation histories and extinction in the central kpc region of a sample of starburst galaxies that have similar far infrared (FIR), 10 micron and K-band luminosities as those of the archetype starburst M82. Our study is based on new optical spectra and previously published K-band photometric data, both sampling the same area around the nucleus. Model starburst spectra were synthesized as a combination of stellar populations of distinct ages formed over the Hubble time, and were fitted to the observed optical spectra and K-band flux. The model is able to reproduce simultaneously the equivalent widths of emission and absorption lines, the continuum fluxes between 3500-7000 Ang, the K-band and the FIR flux. We require a minimum of 3 populations -- (1) a young population of age < 8 Myr, with its corresponding nebular emission, (2) an intermediate-age population (age < 500 Myr), and (3) an old population that forms part of the underlying disk or/and bulge population. The contribution of the old population to the K-band luminosity depends on the birthrate parameter and remains above 60% in the majority of the sample galaxies. Even in the blue band, the intermediate age and old populations contribute more than 40% of the total flux in all the cases. A relatively high contribution from the old stars to the K-band nuclear flux is also apparent from the strength of the 4000 Ang break and the CaII K line. The extinction of the old population is found to be around half of that of the young population. The contribution to the continuum from the relatively old stars has the effect of diluting the emission equivalent widths below the values expected for young bursts. The mean dilution factors are found to be 5 and 3 for the Halpha and Hbeta lines respectively.Comment: 20 pages, uses emulateapj.cls. Scheduled to appear in ApJ Jan 1, 200

Significance Testing of Site 41SS164, San Saba County, Texas

SWCA Environmental Consultants (SWCA) conducted significance testing excavations at site 41SS164, San Saba County, Texas on behalf of the Texas Department of Transportation (TxDOT). The tested portion of the site is in TxDOT’s right-of-way (ROW) of County Road (CR) 228 on the eastern bank of Richland Springs Creek, a tributary of the San Saba River. SWCA performed the investigations under General Services Contract #575XXSA007, Work Authorization #575 21 SA007, and Texas Antiquities Permit 4156. The final report was written under General Services Contract #577XXSA002, Work Authorization #577 05 SA002. In the course of the investigations, SWCA conducted backhoe trenching, hand excavations, special sampling, and other documentation at the project area. As the ROW on the eastern side of the CR 228 bridge is extremely narrow, all trench and hand excavations were conducted in the roadway after the removal of the gravel roadbed and several layers of fill. In all, approximately 3 m3 were excavated by hand at the site, beginning at the transition point between the fill layers and layers containing cultural material, or just above it. In addition to the hand excavations, the testing project included two backhoe trenches excavated perpendicular to each other. As an additional element of the investigations, SWCA excavated one 50-x-50-cm column sample to assess the site’s potential artifact recovery and potential cultural layers. The testing determined that the site contains one intact cultural component, designated Analytical Unit 1 (AU 1), in an alluvial setting. A second deposit containing cultural material above AU 1 was determined to be part of an ambiguous interface fill deposit and not an in situ component. AU 1 contains two burned sandstone rock features, debitage, bone, a dart point, lithic tools, and two charcoal samples. The radiocarbon samples yielded widely disparate dates; one is interpreted as an intrusive sample, and the other found in Feature 2 dated to the Late Archaic. A Pandale dart point dating to the Early/Middle Archaic (8,800–4,000 B.P.) was also found in Feature 2 within AU 1. The deposits appeared to be highly compressed. Geomorphological investigations of the east-west backhoe trench revealed a steady downward slope of cultural material in both AU 1 and the ambiguous interface fill deposit as one approached Richland Springs Creek. Thus, although cultural material was encountered at various depths within the site area, it was identified as one cultural component. Artifact recovery was sparse, with modest amounts of organic material preserved. Although the site contains one analytical unit with prehistoric cultural material in an observable natural stratum, the sloping stratigraphy and complex soil deposition makes it difficult to subdivide the component into more than one occupation period subject to specific research questions. Geomorphic analysis suggests a level of compression in the component. Additionally, the quantity and diversity of cultural material recovered from the site indicates the potential data yield to answer specific research questions is marginal. SWCA recommends that the portion of 41SS164 within the road ROW is not eligible for National Register of Historic Places (NRHP) listing under Criterion D, 36 CFR 60.4, and is not eligible for State Archeological Landmark (SAL) designation under Criteria 1 and 2 of the Rules of Practice and Procedure for the Antiquities Code of Texas, 13 TAC 26.8. Data recovery investigations are not recommended for the portion of the site within the ROW. Portions of the site outside of the ROW have not been fully evaluated

The role of the synchrotron component in the mid infrared spectrum of M 87

We study in detail the mid-infrared Spitzer-IRS spectrum of M 87 in the range 5 to 20 micron. Thanks to the high sensitivity of our Spitzer-IRS spectra we can disentangle the stellar and nuclear components of this active galaxy. To this end we have properly subtracted from the M 87 spectrum, the contribution of the underlying stellar continuum, derived from passive Virgo galaxies in our sample. The residual is a clear power-law, without any additional thermal component, with a zero point consistent with that obtained by high spatial resolution, ground based observations. The residual is independent of the adopted passive template. This indicates that the 10 micron silicate emission shown in spectra of M 87 can be entirely accounted for by the underlying old stellar population, leaving little room for a possible torus contribution. The MIR power-law has a slope alpha ~ 0.77-0.82 (S$_\nu\propto\nu^{-\alpha}$), consistent with optically thin synchrotron emission.Comment: 5 pages, 4 figures, accepted for publication in ApJ main journa

Water vapor radiometry research and development phase

This report describes the research and development phase for eight dual-channel water vapor radiometers constructed for the Crustal Dynamics Project at the Goddard Space Flight Center, Greenbelt, Maryland, and for the NASA Deep Space Network. These instruments were developed to demonstrate that the variable path delay imposed on microwave radio transmissions by atmospheric water vapor can be calibrated, particularly as this phenomenon affects very long baseline interferometry measurement systems. Water vapor radiometry technology can also be used in systems that involve moist air meteorology and propagation studies