Comparative analyses of East Texas forest cover maps generated from Landsat and AVHRR data

Comparing satellite data derived map products are affected by differences in data characteristics, image acquisition dates, processing techniques, and classification schemes used for assigning pixels to a thematic class. By comparing two forest maps generated from Landsat Enhanced Thematic Mapper Plus (ETM+) and Advanced Very High Resolution Radiometer (AVHRR) images acquired on the same day, and processed using identical classification scheme and methods these differences were minimized. The ETM+ derived map had higher classification accuracy values and more precise area estimates than the AVHRR derived map. In the ETM+ derived map, 87 of the 599 verification data were misclassified, whereas in the AVHRR derived map, 155 of the 469 verification data were misclassified. Detailed error analyses by land cover class revealed that a land use based definition of forest accounted for 74% (64 out of 87) and 57% (89 out of 155) of the classification errors in ETM+ and AVHRR derived maps, respectively.     

A Lost Realm in the Internal Domains of the Betic-Rif Orogen (Spain and Morocco): Evidence from Conglomerates and Consequences for Alpine Geodynamic Evolution

The Malaguide-Ghomaride Complex is capped by Upper Oligocene-Aquitanian clastic deposits postdating early Alpine orogenesis but predating the main tectonic-metamorphic evolution, end of nappe emplacement, unroofing, and exhumation of the metamorphic units of the Betic-Rif Orogen. Two conglomerate intervals within these deposits are characterized by clasts of sedimentary, epimetamorphic, and mafic volcanic rocks derived from Malaguide-Ghomaride units and by clasts of acidic magmatic and orthogneissic rocks of unknown provenance, here studied. Magmatic rocks originated from late-Variscan two-mica cordierite-bearing granitoids and, subordinately, from aplitic dikes. Orthogneisses derive from similar plutonic rocks but are affected by an Alpine metamorphic overprint evolving from greenschist (T=510&j0;-530 degrees C and P=5-6 kbar) to low-temperature amphibolite facies (T>550&j0;C and P<3 kbar). Such a plutonic rock suite is unknown in any Betic-Rif unit or in the basement of the Alboran Sea, and the metamorphic evolution in the orthogneisses is different from (and older than) that of Alpujarride-Sebtide rocks to which they were formerly ascribed. Magmatic and metamorphic rocks very similar to those studied characterize the basements of some Kabylia and Calabria-Peloritani units. Therefore, the source area is a currently lost continental-crust realm of Calabria-Peloritani-Kabylia type, located to the ESE of the Malaguide-Ghomaride Domain and affected by a pre-latest Oligocene Alpine metamorphism. Increasingly active tectonics transformed this realm into rising areas from which erosion fed small subsiding synorogenic basins formed on the Malaguide-Ghomaride Complex. This provenance analysis demonstrates that all these domains constituted a single continental-crust block until Aquitanian-Burdigalian times, before its dispersal around nascent western Mediterranean basins.     

Preliminary Photometric Evidence of Starspot Umbrae and Penumbrae on Late-Type Active Stars

We constrain the properties of the spotted regions on the photosphere of the active late-type star DX Leonis by comparing the observed amplitudes of light and color variations with synthetic amplitudes obtained by means of Dorren's spot model and computed for a grid of values of spot temperatures, areas and latitudes.     

Characterization of the Frictional Behavior of Steel-Polymer Interfaces with Pronounced Stick-Slip Effect for Use in Seismic Isolation

Bulletin of Earthquake Engineering - The frictional behavior of steel-PTFE interfaces for use in seismic isolation has been studied extensively in the past. However, alternative polymers, such as...     

Photoluminescence properties of S<Subscript>2</Subscript> molecule trapped in Melanophlogite

We studied the photoluminescence properties of a sample of SiO₂-clathrate Melanophlogite, a crystalline microporous material which is found in nature as a rare mineral. Upon β irradiation, the material displays an intense light emission under near-UV illumination. We studied in detail this optical activity by steady-state and time-resolved photoluminescence measurements as a function of temperature. The spectroscopic properties we find can be ascribed to a population of quasi-free molecules trapped within each of the two different types of cage available in the structure of this clathrate, although the spectroscopic properties of the guest molecules are affected by their interactions with the host matrix. Based on the available data, we attribute the observed photoluminescence to trapped S₂ molecules, emitting from their excited ³Σ _u ^? or ³Π _u electronic states, depending on the cage they are trapped in and on temperature. Our results have an impact on the fundamental understanding of host–guest interactions characteristic of microporous systems such as clathrates. Indeed, the data highlight that even a relatively weak coupling between quasi-free S₂ molecules and the two types of cages provided by the Melanophlogite host has a surprisingly complex influence on the optical properties of the guest.     

Magnetic activity on 12 Cam and 29 Dra from long‐term photometry

We present newly discovered magnetic cycles of two late‐type and long‐period SB1 systems: 12 Cam and 29 Dra. The long‐term photometry study revealed the presence of magnetic multiperiodic cycles on both stars, namely 14.8 and 8.5 yr for 12 Cam and 20.3, 11.1, and 7.6 yr for 29 Dra. Furthermore, the modelling of the V ‐band light curves revealed the existence of two active longitudes on 12 Cam and probably on 29 Dra as well. Both stars show changes of rotational period. The 12 Cam is the slowest rotating star whose activity cycle has been determined. The activity cycles determined by us allow us to extend to the slower rotation regime and to improve the significance of the empirical relation between rotation period and magnetic cycle length (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Landslide risk assessment

Landslide risk can be assessed by evaluating geological conditions associated with past events. A sample of 2,4 16 slides from urban areas in West Virginia, each with 12 associated geological factors, has been analyzed using SAS computer methods. In addition, selected data have been normalized to account for areal distribution of rock formations, soil series, and slope percents. Final calculations yield landslide risk assessments of <0.50=low risk, 0.50 to 1.50=moderate risk, and >1.50=high risk. The simplicity of the method provides for a rapid, initial assessment prior to financial investment. However, it does not replace on-site investigations, nor excuse poor construction.     

Photospheric Magnetic Activity in a Proxy for the Young Sun: HD 134319

We present the results of a long-term photometric monitoring of the young single main-sequence star HD134319. It shows short-term variability of the optical-band continuum flux with a period of 4.448 days. The variability is attributed to dark spots or spots groups unevenly distributed in longitude on the star's photosphere, whose visibility is modulated by the star's rotation. Maps of the photospheric spot pattern have been obtained with light curve inversion techniques based on the Maximum Entropy and the Tikhonov regularization criteria. The overall spot pattern shows evidence for two long-lasting active longitudes located about 180° apart, with a total area of at least 16% of the stellar surface (assuming an inclination of the stellar rotation axis of 90° on the line of sight). The longitude distribution of the spot pattern and its total area do not show any clear evidence for a long-term variation along the five years of observations. A comparison with recent mean field dynamo models is also addressed, suggesting a possible interpretation of such a behaviour. Singularity, spectral type, youth and a high level of photospheric and chromospheric activity make HD134319 a suitable proxy for studying the magnetic activity of the young Sun not far after its arrival on the zero age main sequence.     

Terrain analysis of the Racetrack Basin and the sliding rocks of Death Valley

The Racetrack Playa's unusual surface features known as sliding rocks have been the subject of an ongoing debate and several mapping projects for half a century, although the causative mechanism remains unresolved. Clasts ranging in volume from large pebbles to medium boulders have, unwitnessed, maneuvered around the nearly flat dry lake over considerable distances. The controversy has persisted partly because eyewitness accounts of the phenomenon continue to be lacking, and the earlier mapping missions were limited in method and geographic range. In July 1996, we generated the first complete map of all observed sliding rock trails by submeter differential Global Positioning System (DGPS) mapping technology. The resulting map shows 162 sliding rocks and associated trails to an accuracy of approximately 30 cm. Although anemometer data are not available in the Racetrack wilderness, wind is clearly a catalyst for sliding rock activity; an inferred wind rose was constructed from DGPS trail segment data. When the entire trail network is examined in plan, some patterns emerge, although other (perhaps expected relations) remain elusive: terrain analysis of the surrounding topography demonstrates that the length and morphology of trails are more closely related to where rocks rested at the onset of motion than to any physical attribute of the rocks themselves. Follow-up surveys in May 1998, May 1999, August 1999, and November 1999 revealed little modification of the July, 1996 sliding rock configuration. Only four rocks were repositioned during the El Niño winter of 1997–1998, suggesting that activity may not be restricted to winter storms.     

The large-scale structure of the universe in skewed cold dark matter models

We present results from N-body simulations of the clustering properties of the universe in a cubic box of size 260h⁻¹ Mpc, within a cold dark matter (CDM) cosmology with skewed distributions for initial adiabatic density perturbations δ_M. We consider two non-Gaussian models, Chi-squared and Lognormal, where the primordial gravitational potential is obtained from a non-linear transformation on a Gaussian random field. Our procedure yields for each model two primordial density distributions with opposite skewness δ³_M. The gravitational evolution and the present statistical properties of our simulations are strongly sensitive to the sign of the initial skewness. Skew-positive simulations produce a highly lumpy distribution with little power on large scales. Skew-negative simulations, on the contrary, evolve towards a cellular structure with high power on large scales, showing, in many respects, better agreement with observations than the standard CDM model. Giving up the random-phase hypothesis for primordial perturbations seems then a viable possibility to reproduce the large-scale properties of the universe; such a possibility is further motivated by many physical models either within the inflationary dynamics or phase transitions in the early universe.