298 research outputs found
Spatial and temporal dynamics of stream chemistry in a forested watershed
Spatial dynamics of solute chemistry and natural abundance isotopes of nitrate (15N and 18O) were examined in seven locations and at the watershed outlet in 2001 and 2002 in a forest watershed in the Adirondack Mountains of New York State, USA. Temporal dynamics were examined during five discharge periods: winter, snowmelt, spring, summer, and fall, based on discharge levels at the watershed outlet. Solute concentrations were variable across space and time with significant (pâ€0.05) interaction effects. Year*period was significant for pH, NH4+, NO3-, total N, DOC, and total Al suggesting that inter-annual variability in discharge levels was more important for these solutes than intra-annual variability. Period*sampling point was significant for pH, Mg2+, Ca2+, sum of base cations, Si, and total Al suggesting that the differences in concentration of these solutes among sampling points were moderated by discharge levels. In general, groundwater sources located in upper watershed controlled stream chemistry at higher elevations with highest pH, Ca2+, sum of base cations, Si, and SO42- concentrations, with higher values in summer, and dilution effects during snowmelt. Two low elevation wetlands had a substantial influence over stream chemistry at those locations contributing lowest NO3- and highest DOC. Snowmelt exhibited among the lowest pH, sum of base cations, and SO42-, and highest NO3-, total N, and total Al; snowmelt appeared to dilute groundwater, and flush stored soil-derived solutes. Summer discharge, composed mainly of groundwater, exhibited the lowest flow, among the highest Mg2+, Ca2+, and lowest DON, DOC, and total Al concentrations. Isotopic analysis indicated that NO3-was microbial with primary source in upper watershed soil, from where it was flushed to stream under high discharge-conditions, or drained to groundwater which became its secondary source when discharge was low. Watershed outlet did not exhibit specific solute levels found at source-areas, but represented solute dynamics in the rest of the watershed well
Non-equilibrium hysteresis and spin relaxation in the mixed-anisotropy dipolar coupled spin-glass LiHoErF
We present a study of the model spin-glass LiHoErF using
simultaneous AC susceptibility, magnetization and magnetocaloric effect
measurements along with small angle neutron scattering (SANS) at sub-Kelvin
temperatures. All measured bulk quantities reveal hysteretic behavior when the
field is applied along the crystallographic c axis. Furthermore avalanche-like
relaxation is observed in a static field after ramping from the
zero-field-cooled state up to Oe. SANS measurements are employed to
track the microscopic spin reconfiguration throughout both the hysteresis loop
and the related relaxation. Comparing the SANS data to inhomogeneous mean-field
calculations performed on a box of one million unit cells provides a real-space
picture of the spin configuration. We discover that the avalanche is being
driven by released Zeeman energy, which heats the sample and creates positive
feedback, continuing the avalanche. The combination of SANS and mean-field
simulations reveal that the conventional distribution of cluster sizes is
replaced by one with a depletion of intermediate cluster sizes for much of the
hysteresis loop.Comment: 6 pages, 4 figure
Application of new methods of environment analysis and assessment in landscape audits : case studies of urban areas like Czestochowa, Poland
Following the 2000 European Landscape Convention, a new act strengthening landscape protection
instruments has been in force since 2015. It sets forth legal aspects of landscape shaping (Dziennik Ustaw 2015, poz.
774) and introduces landscape audits at the province level. A landscape audit consists in identification and
characterization of selected landscapes, assessment of their value, selection of so-called priority landscapes and
identification of threats for preservation of their value. An audit complies with GIS standards. Analyses use source
materials, i.e. digital maps of physical-geographical mesoregions, current topographic maps of digital resources of
cartographic databases, latest orthophotomaps and DTMs, maps of potential vegetation, geobotanic regionalization,
historic-cultural regionalization and natural landscape types, documentation of historical and cultural values and
related complementary resources. A special new methodology (Solon et al. 2014), developed for auditing, was tested
in 2015 in an urban area (Myga-Piatek et al. 2015). Landscapes are characterized by determining their analytic
(natural and cultural) and synthetic features, with particular focus on the stage of delimitation and identification of
landscape units in urban areas. Czestochowa was selected as a case study due to its large natural (karst landscapes of
the Czestochowa Upland, numerous forests, nature reserves) and cultural (Saint Maryâs Sanctuary, unique urban
architecture) potential. Czestochowa is also a city of former iron ore and mineral resources exploitation, still active
industry, dynamic urban sprawl within former farming areas, and dynamically growing tourism. Landscape
delimitation and identification distinguished 75 landscape units basing on uniform landscape background (uniform
cover and use of the land). Landscape assessment used a new assessment method for anthropogenic transformation of
landscape â the indicator describing the correlation between the mean shape index (MSI) and the Shannon diversity
index (SHDI) (Pukowiec-Kurda, Sobala 2016). Particular threats and planning suggestions, useful in development of
urban areas, were presented for selected priority landscapes
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Life in the Atacama â Year 2: Geologic reconnaissance through long-range roving and implications on the search for life
The Life in the Atacama-2004 project, which included geological, morphological, and mineralogical mapping through combined satellite, field-based, and microscopic perspectives and long-range roving, led to the localization of potential habitats
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Spectroscopic results from the Life in the Atacama (LITA) project 2004 field season
Analysis of spectroscopy datasets from rover field tests in the Atacama Desert (Chile), focusing on the composition of the surface and identification of potential habitats for life
Spectral evidence of size dependent space weathering processes on asteroid surfaces
Most compositional characterizations of the minor planets are derived from analysis of visible and near-infrared reflectance spectra. However, such spectra are derived from light which has only interacted with a very thin surface layer. Although regolith processes are assumed to mix all near-surface lithologic units into this layer, it has been proposed that space weathering processes can alter this surface layer to obscure the spectral signature of the bedrock lithology. It has been proposed that these spectral alteration processes are much less pronounced on asteroid surfaces than on the lunar surface, but the possibility of major spectral alteration of asteroidal optical surfaces has been invoked to reconcile S-asteroids with ordinary chondrites. The reflectance spectra of a large subset of the S-asteroid population have been analyzed in a systematic investigation of the mineralogical diversity within the S-class. In this sample, absorption band depth is a strong function of asteroid diameter. The S-asteroid band depths are relatively constant for objects larger than 100 km and increase linearly by factor of two toward smaller sizes (approximately 40 km). Although the S-asteroid surface materials includes a diverse variety of silicate assemblages, ranging from dunites to basalts, all compositional subtypes of the S-asteroids conform to this trend. The A-, R-, and V-type asteroids which are primarily silicate assemblages (as opposed to the metal-silicate mixtures of most S-asteroids) follow a parallel but displaced trend. Some sort of textural or regolith equilibrium appears to have been attained in the optical surfaces of asteroids larger than about 100 km diameter but not on bodies below this size. The relationships between absorption band depth, spectral slope, surface albedo and body size provide an intriguing insight into the nature of the optical surfaces of the S-asteroids and space weathering on these objects
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Searching for life with rovers: exploration methods and science results from the 2004 field campaign of the âLife in the Atacamaâ project and applications to future Mars Missions
LITA develops and field tests a long-range automated rover and a science payload to search for microbial life in the Atacama. The Atacama's evolution provides a unique training ground for designing and testing exploration strategies and life detection methods for the search for life on Mars
New Optical Reddening Maps of the Large and Small Magellanic Clouds
We present new reddening maps of the SMC and LMC based on the data of the
third phase of the Optical Gravitational Lensing Experiment (OGLE III). We have
used two different methods to derive optical reddening maps. We adopt a
theoretical mean unreddened colour for the red clump in the SMC and LMC,
respectively. We subdivide the photometric data for both Clouds into subfields
and calculate the difference between the observed red clump position and the
theoretical value for each field, which provides us with the reddening value in
(V-I). Furthermore reddening values are obtained for 13490 LMC RR Lyrae ab and
1529 SMC RR Lyrae ab stars covering the whole OGLE III region of the MCs. The
observed colours (V-I) of the RR Lyrae stars are compared with the colour from
the absolute magnitudes. The absolute magnitude of each RR Lyrae star is
computed using its period and metallicity derived from Fourier decomposition of
its lightcurve. In general we find a low and uniform reddening distribution in
both Magellanic Clouds. The red clump method indicates a mean reddening of the
LMC of E(V-I) = 0.09 +/- 0.07 mag, while for the SMC E(V-I) = 0.04 +/- 0.06 mag
is obtained. With RR Lyrae stars a median value of E(V-I) = 0.11 +/- 0.06 mag
for the LMC and E(V-I) = 0.07 +/- 0.06 mag for the SMC is found. The LMC shows
very low reddening in the bar region, whereas the reddening in the star-forming
leading edge and 30 Doradus is considerably higher. In the SMC three pronounced
regions with higher reddening are visible. Two are located along the bar, while
the highest reddening is found in the star-forming wing of the SMC. In general
the regions with higher reddening are in good spatial agreement with infrared
reddening maps as well as with reddening estimations of other studies. The
position-dependent reddening values from the red clump method are available via
the Virtual Observatory interface.Comment: 15 pages, 22 Figures, AJ publishe
Phase diagram with an enhanced spin-glass region of the mixed Ising-<em>XY</em> magnet LiHo<sub><em>x</em></sub>Er<sub>1<em>-x</em></sub>F<sub>4</sub>
We present the experimental phase diagram of LiHoxEr1 xF4, a dilution series of dipolar coupled model magnets. The phase diagram was determined using a combination of ac susceptibility and neutron scattering. Three unique phases in addition to the Ising ferromagnet LiHoF4 and the XY antiferromagnet LiErF4 have been identified. Below x 0.86, an embedded spin glass phase is observed, where a spin glass exists within the ferromagnetic structure. Below x 0.57, an Ising spin glass is observed consisting of frozen needlelike clusters. For x amp; 8764; 0.3 0.1, an antiferromagnetically coupled spin glass occurs. A reduction of TC x for the ferromagnet is observed which disobeys the mean field predictions that worked for LiHoxY1 xF4
On the isolated dwarf galaxies: from cuspy to flat dark matter density profiles and metallicity gradients
The chemodynamical evolution of spherical multi-component self-gravitating
models for isolated dwarf galaxies is studied. We compare their evolution with
and without feedback effects from star formation processes. We find that
initially cuspy dark matter profiles flatten with time as a result of star
formation, without any special tuning conditions. Thus the seemingly flattened
profiles found in many dwarfs do not contradict the cuspy profiles predicted by
cosmological models. We also calculate the chemical evolution of stars and gas,
to permit comparisons with observational data.Comment: Accepted the 28/01/1
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