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2010

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Articles 6331 - 6360 of 8625

Full-Text Articles in Physical Sciences and Mathematics

Cobalt Nanoclusters On Metal-Supported Xe Monolayers: Influence Of The Substrate On Cluster Formation Kinetics And Magnetism, V. Sessi, K. Kuhnke, J. Zhang, Jan Honolka, Klaus Kern, Axel Enders, P. Bencok, S. Bornemann, Ján Minár, Hubert Ebert Jan 2010

Cobalt Nanoclusters On Metal-Supported Xe Monolayers: Influence Of The Substrate On Cluster Formation Kinetics And Magnetism, V. Sessi, K. Kuhnke, J. Zhang, Jan Honolka, Klaus Kern, Axel Enders, P. Bencok, S. Bornemann, Ján Minár, Hubert Ebert

Axel Enders Publications

The growth dynamics of submonolayer coverages of cobalt during buffer layer assisted growth on Ag(111) and Pt(111) substrates is investigated by variable temperature scanning tunneling microscopy in the temperature range between 80 and 150 K. It is found that attractive cluster-substrate interactions can govern the cluster formation on the Xe buffer layer if the Xe layer is sufficiently thin. The interpretation of the microscopy results is supported by x-ray magnetic circular dichroism data which monitor the effect of cluster-substrate interactions on the formation of magnetic moments and magnetic anisotropy of Co nanocluster during the different stages of growth. Ab initio …

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Seasonal Ice Cycle At The Mars Phoenix Landing Site: 2. Postlanding Crism And Ground Observations, Selby Cull, R. E. Arvidson, R. V. Morris, M. Wolff, M. T. Mellon, M. T. Lemmon Jan 2010

Seasonal Ice Cycle At The Mars Phoenix Landing Site: 2. Postlanding Crism And Ground Observations, Selby Cull, R. E. Arvidson, R. V. Morris, M. Wolff, M. T. Mellon, M. T. Lemmon

Geology Faculty Research and Scholarship

The combination of ground observations from the Mars Phoenix Lander and orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provided a detailed view of the formation of late summer surface water ice at the landing site and surrounding regions. CRISM observations of the landing site during and immediately after Phoenix operations were analyzed to track the seasonal and diurnal ice cycles during the late spring to late summer, and a nonlinear mixing model was used to estimate grain sizes and relative abundances of water ice and dust. The surface around the Phoenix landing site was ice-free from …

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Seasonal H2o And Co2 Ice Cycles At The Mars Phoenix Landing Site: 1. Prelanding Crism And Hirise Observations, Selby Cull, Raymond E. Arvidson, Michael Mellon, Sandra Wiseman, Roger Clark, Timothy Titus, Richard V. Morris, Patrick Mcguire Jan 2010

Seasonal H2o And Co2 Ice Cycles At The Mars Phoenix Landing Site: 1. Prelanding Crism And Hirise Observations, Selby Cull, Raymond E. Arvidson, Michael Mellon, Sandra Wiseman, Roger Clark, Timothy Titus, Richard V. Morris, Patrick Mcguire

Geology Faculty Research and Scholarship

The condensation, evolution, and sublimation of seasonal water and carbon dioxide ices were characterized at the Mars Phoenix landing site from Martian northern midsummer to midspring (Ls ∼ 142° – Ls ∼ 60°) for the year prior to the Phoenix landing on 25 May 2008. Ice relative abundances and grain sizes were estimated using data from the Compact Reconnaissance Imaging Spectrometer for Mars and High Resolution Imaging Science Experiment aboard Mars Reconnaissance Orbiter and a nonlinear mixing model. Water ice first appeared at the Phoenix landing site during the afternoon in late summer (Ls ∼ 167°) as …

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Compositions Of Subsurface Ices At The Mars Phoenix Landing Site, Selby Cull, Raymond E. Arvidson, Michael T. Mellon, Philip Skemer, Amy Shaw, Richard V. Morris Jan 2010

Compositions Of Subsurface Ices At The Mars Phoenix Landing Site, Selby Cull, Raymond E. Arvidson, Michael T. Mellon, Philip Skemer, Amy Shaw, Richard V. Morris

Geology Faculty Research and Scholarship

NASA's Phoenix Lander uncovered two types of ice at its 2008 landing site on the northern plains of Mars: a brighter, slab-like ice that broke during Robotic Arm operations; and a darker icy deposit. Spectra from the Phoenix Surface Stereo Imager (SSI) are used to demonstrate that the brighter material consists of nearly pure water ice, which probably formed by migration and freezing of liquid water. The darker icy material consists of similar to 30 +/- 20 wt% ice, with the remainder composed of fine-grained soil, indicating that it probably formed as pore ice. These two types of ice represent …

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Rotational Doppler Effect In Magnetic Resonance, S Ledinez, Eugene M. Chudnovsky, Javier Tejada Jan 2010

Rotational Doppler Effect In Magnetic Resonance, S Ledinez, Eugene M. Chudnovsky, Javier Tejada

Publications and Research

We compute the shift in the frequency of the spin resonance in a solid that rotates in the field of a circularly polarized electromagnetic wave. Electron spin resonance, nuclear magnetic resonance, and ferromagnetic resonance are considered. We show that contrary to the case of the rotating LC circuit, the shift in the frequency of the spin resonance has strong dependence on the symmetry of the receiver. The shift due to rotation occurs only when rotational symmetry is broken by the anisotropy of the gyromagnetic tensor, by the shape of the body, or by magnetocrystalline anisotropy. General expressions for the resonance …

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Edges And Diffractive Effects In Casimir Energies, Daniel N. Kabat, Dimitra Karabali, V P. Nair Jan 2010

Edges And Diffractive Effects In Casimir Energies, Daniel N. Kabat, Dimitra Karabali, V P. Nair

Publications and Research

The prototypical Casimir effect arises when a scalar field is confined between parallel Dirichlet boundaries. We study corrections to this when the boundaries themselves have apertures and edges. We consider several geometries: a single plate with a slit in it, perpendicular plates separated by a gap, and two parallel plates, one of which has a long slit of large width, related to the case of one plate being semi-infinite. We develop a general formalism for studying such problems, based on the wavefunctional for the field in the gap between the plates. This formalism leads to a lower dimensional theory defined …

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Single Magnetic Molecule Between Conducting Leads: Effect Of Mechanical Rotations, Reem Jaafar, Eugene M. Chudnovsky, Dmitry A. Garanin Jan 2010

Single Magnetic Molecule Between Conducting Leads: Effect Of Mechanical Rotations, Reem Jaafar, Eugene M. Chudnovsky, Dmitry A. Garanin

Publications and Research

We study spin-rotation effects in a magnetic molecule bridge d between two conducting leads. Dy- namics of the total angular momentum couples spin tunneling to the mechanical rotations. Landau- Zener spin transition produced by the time-dependent magne tic field generates a unique pattern of mechanical oscillations that can be detected by measuring t he electronic tunneling current through the molecule.

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Optical Characterization Of Silver Doped Poly (Vinyl Alcohol) Films, W. A. Jabbar, N. F. Habubi, S. S. Chiad Jan 2010

Optical Characterization Of Silver Doped Poly (Vinyl Alcohol) Films, W. A. Jabbar, N. F. Habubi, S. S. Chiad

Journal of the Arkansas Academy of Science

Silver-doped PVA films were prepared by casting method in order to study the effect of silver on the optical properties of poly(vinyl alcohol) using UV/VIS spectroscopy. It was found that these thin films have an indirect optical band gap (2.4-1.3) eV as the doping percentage increase. Extinction coefficient and refractive index increase as the doping percentage increase, while in general the optical dispersion parameters show an opposite behavior with doping

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Characterization Of Secondary Organic Aerosol (Soa) Formed By The Reaction Of Β-Caryophyllene, Soot And Ozone: Climate Impact, A. Sarkar, N. A. Marley, J. S. Gaffney Jan 2010

Characterization Of Secondary Organic Aerosol (Soa) Formed By The Reaction Of Β-Caryophyllene, Soot And Ozone: Climate Impact, A. Sarkar, N. A. Marley, J. S. Gaffney

Journal of the Arkansas Academy of Science

Diesel soot (black carbon, BC) is an important light absorbing aerosol component in atmosphere that can cause tropospheric heating. Laboratory studies have found it to be unreactive to ozone at ambient temperature. The low uptake coefficient i.e., γ 300 K = 2× 10-7 , of the soot-O3 reaction indicates a low probability of irreversible O3 loss from gas phase to surface-adsorbed product (Particle phase). This shows clearly that at low temperature soot is not reactive with atmospheric oxidants. In contrast, sesquiterpenes (SQT) such as β-caryophyllene (C15H24), which are produced primarily by plants, are extremely reactive with ozone. For example, the …

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A New Class Of Attacks On Time Series Data Mining, Ye Zhu, Yongjian Fu, Huirong Fu Jan 2010

A New Class Of Attacks On Time Series Data Mining, Ye Zhu, Yongjian Fu, Huirong Fu

Electrical and Computer Engineering Faculty Publications

Traditional research on preserving privacy in data mining focuses on time-invariant privacy issues. With the emergence of time series data mining, traditional snapshot-based privacy issues need to be extended to be multi-dimensional with the addition of time dimension. We find current techniques to preserve privacy in data mining are not effective in preserving time-domain privacy. We present the data flow separation attack on privacy in time series data mining, which is based on blind source separation techniques from statistical signal processing. Our experiments with real data show that this attack is effective. By combining the data flow separation method and …

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Forensic Analysis Of The Windows 7 Registry, Khawla Abdulla Alghafli, Andrew Jones, Thomas Anthony Martin Jan 2010

Forensic Analysis Of The Windows 7 Registry, Khawla Abdulla Alghafli, Andrew Jones, Thomas Anthony Martin

Australian Digital Forensics Conference

The recovery of digital evidence of crimes from storage media is an increasingly time consuming process as the capacity of the storage media is in a state of constant growth. It is also a difficult and complex task for the forensic investigator to analyse all of the locations in the storage media. These two factors, when combined, may result in a delay in bringing a case to court. The concept of this paper is to start the initial forensic analysis of the storage media in locations that are most likely to contain digital evidence, the Windows Registry. Consequently, the forensic …

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The 2010 Personal Firewall Robustness Evaluation, Satnam Singh Bhamra Jan 2010

The 2010 Personal Firewall Robustness Evaluation, Satnam Singh Bhamra

Australian Digital Forensics Conference

With the advent of cheaper Internet connections, the number of Internet connections among home users is on the rise. Generally, home users have little understanding of the security concerns associated with Internet connectivity. To protect against computer attacks, generally a home user may install a personal firewall on his/her computer. To determine the effectiveness of personal firewalls, evaluation tests were performed against the ten firewall products available to users at local electronic stores and listed on popular firewall security websites. The firewalls were tested in their default and maximum security mode. The investigation was carried out by performing a port …

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Cyber Forensics Assurance, Glenn S. Dardick Jan 2010

Cyber Forensics Assurance, Glenn S. Dardick

Australian Digital Forensics Conference

As the usage of Cyber Forensics increases, so does the potential for errors in the practice of applying Cyber Forensic. Errors in opinions derived from faulty practices have resulted in grievous miscarriages of justice. However, utilizing the foundations of Information Systems Assurance and Information Quality, a solid foundation for improving the quality and effectiveness of Cyber Forensics can be derived. The foundations of Information Systems Assurance and information Quality provide a solid foundation for improving the current efforts in Cyber Forensics. With increasing computer and network systems usage as well as the increasing frequency of attacks on information systems, the …

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An Investigation Into The Efficacy Of Three Erasure Tools Under Windows 7, Cheng Toy Chiang, Kelvin Triton, Andrew Woodward Jan 2010

An Investigation Into The Efficacy Of Three Erasure Tools Under Windows 7, Cheng Toy Chiang, Kelvin Triton, Andrew Woodward

Australian Digital Forensics Conference

This paper examined three erasure software tools aimed at removing evidence of online and other activity, and was investigated using the Windows 7 operating system as the test platform. The tools in question were Anti- Tracks, Free Internet Eraser and Free Internet Window Washer. The findings included each of the tested software’s ability to completely erase target data on the drive. It also included examined whether the data was erased or merely the link to the data was deleted, making the file recoverable. It was found that the Anti-Tracks program did not erase any of the information targeted by the …

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The Similarity Problem For Indefinite Sturm-Liouville Operators With Periodic Coefficients, Aleksey Kostenko Jan 2010

The Similarity Problem For Indefinite Sturm-Liouville Operators With Periodic Coefficients, Aleksey Kostenko

Articles

We investigate the problem of similarity to a self-adjoint operator for $J$-positive Sturm-Liouville operators $L=\frac{1}{\omega}(-\frac{d^2}{dx^2}+q)$ with $2\pi$-periodic coefficients $q$ and $\omega$. It is shown that if 0 is a critical point of the operator $L$, then it is a singular critical point. This gives us a new class of $J$-positive differential operators with the singular critical point 0. Also, we extend the Beals and Parfenov regularity conditions for the critical point $\infty$ to the case of operators with periodic coefficients.

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Seasonal And Salinity Effects On The Distribution Of Higher Filamentous Marine Fungi At Rookery Bay, Fl., Julia Ossler Jan 2010

Seasonal And Salinity Effects On The Distribution Of Higher Filamentous Marine Fungi At Rookery Bay, Fl., Julia Ossler

HCNSO Student Theses and Dissertations

More than 500 species of higher marine fungi in over 300 genera have been described. Many marine fungi are highly specialized for marine environments relative to their terrestrial counterparts, having appendaged ascospores and conidia to aid in buoyancy, entrapment, and adherence to substrates. They have been reported to inhabit a wide variety of substrates including decaying wood, leaves, calcareous and chitinous substrates, seaweeds, and seagrasses. Most early studies on marine fungi were carried out in temperate regions. Investigations have now shifted to tropical locations in order to better evaluate the abundance and diversity of marine fungi on a global basis. …

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Synthesis And Manufacture Of Photocrosslinkable Poly(Caprolactone)-Based 3d Scaffolds For Tissue Engineering Applications, Nathan Jonathan Castro Jan 2010

Synthesis And Manufacture Of Photocrosslinkable Poly(Caprolactone)-Based 3d Scaffolds For Tissue Engineering Applications, Nathan Jonathan Castro

Open Access Theses & Dissertations

It is known that the body can efficiently repair hard tissue (bone) micro fractures by suturing the defect through the deposition of minerals resulting in an area that is stronger post-injury. Larger defects, however, generally cause more trouble since the body is incapable of repairing them. Bone defects can occur as a result of congenital abnormalities, trauma, or disease. Traditional methods for addressing these defects have involved the use of acellular cadaverous bone or autologous bone. Both contain innate problems associated with them; the former method can result in disease transmission, as well as very low integration with the host …

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Barcoding Bushmeat: Molecular Identification Of Central African And South American Harvested Vertebrates, Mitchell J. Eaton, Greta J. Meyers, Sergios-Orestis Kolokotronis, Matthew S. Leslie, Andrew P. Martin, George Amato Jan 2010

Barcoding Bushmeat: Molecular Identification Of Central African And South American Harvested Vertebrates, Mitchell J. Eaton, Greta J. Meyers, Sergios-Orestis Kolokotronis, Matthew S. Leslie, Andrew P. Martin, George Amato

United States Geological Survey: Staff Publications

The creation and use of a globally available database of DNA sequences from a standardized gene region has been proposed as a tool for species identification, assessing genetic diversity and monitoring the legal and illegal trade in wildlife species. Here, we contribute to the Barcode of Life Data System and test whether a short region of the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene would reliably distinguish among a suite of commonly hunted African and South American mammal and reptile species. We used universal primers to generate reference barcode sequences of 645 bp for 23 species from five vertebrate …

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Barcoding Bushmeat: Molecular Identification Of Central African And South American Harvested Vertebrates, Mitchell J. Eaton, Greta L. Meyers, Sergios-Orestis Kolokotronis, Matthew S. Leslie, Andrew P. Martin, George Amato Jan 2010

Barcoding Bushmeat: Molecular Identification Of Central African And South American Harvested Vertebrates, Mitchell J. Eaton, Greta L. Meyers, Sergios-Orestis Kolokotronis, Matthew S. Leslie, Andrew P. Martin, George Amato

United States Geological Survey: Staff Publications

The creation and use of a globally available database of DNA sequences from a standardized gene region has been proposed as a tool for species identification, assessing genetic diversity and monitoring the legal and illegal trade in wildlife species. Here, we contribute to the Barcode of Life Data System and test whether a short region of the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene would reliably distinguish among a suite of commonly hunted African and South American mammal and reptile species. We used universal primers to generate reference barcode sequences of 645 bp for 23 species from five vertebrate …

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Development And Application Of A Pollen-Based Paleohydrologic Reconstruction From The Lower Roanoke River Basin, North Carolina, Usa, Debra Willard, Christopher Bernhardt, Roger Brown, Bryan Landacre, Philip A. Townsend Jan 2010

Development And Application Of A Pollen-Based Paleohydrologic Reconstruction From The Lower Roanoke River Basin, North Carolina, Usa, Debra Willard, Christopher Bernhardt, Roger Brown, Bryan Landacre, Philip A. Townsend

United States Geological Survey: Staff Publications

We used pollen assemblages to reconstruct late-Holocene paleohydrologic patterns in floodplain deposits from the lower Roanoke River basin (North Carolina, southeastern USA). Using 120 surface samples from 38 transects, we documented statistical relationships between pollen assemblages, vegetation, and landforms. Backswamp pollen assemblages (long hydroperiods) are dominated by Nyssa (tupelo) and Taxodium (cypress) and have high pollen concentrations. Sediments from elevated levees and seasonally flooded forests (shorter hydroperiods) are characterized by dominant Pinus (pine) pollen, variable abundance of hardwood taxa, and low pollen concentrations. We apply the calibration data set to interpret past vegetation and paleohydrology. Pollen from a radiocarbon-dated sediment …

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Abandoned Mine Drainage In The Swatara Creek Basin, Southern Anthracite Coalfield, Pennsylvania, Usa: 2. Performance Of Treatment Systems, Charles A. Cravotta Iii Jan 2010

Abandoned Mine Drainage In The Swatara Creek Basin, Southern Anthracite Coalfield, Pennsylvania, Usa: 2. Performance Of Treatment Systems, Charles A. Cravotta Iii

United States Geological Survey: Staff Publications

A variety of passive and semi-passive treatment systems were constructed by state and local agencies to neutralize acidic mine drainage (AMD) and reduce the transport of dissolved metals in the upper Swatara Creek Basin in the Southern Anthracite Coalfield in eastern Pennsylvania. To evaluate the effectiveness of selected treatment systems installed during 1995–2001, the US Geological Survey collected water-quality data at upstream and downstream locations relative to each system eight or more times annually for a minimum of 3 years at each site during 1996– 2007. Performance was normalized among treatment types by dividing the acid load removed by the …

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Abandoned Mine Drainage In The Swatara Creek Basin, Southern Anthracite Coalfield, Pennsylvania, Usa: 1. Stream Water Quality Trends Coinciding With The Return Of Fish, Charles A. Cravotta Iii, Robin A. Brightbill, Michael J. Langland Jan 2010

Abandoned Mine Drainage In The Swatara Creek Basin, Southern Anthracite Coalfield, Pennsylvania, Usa: 1. Stream Water Quality Trends Coinciding With The Return Of Fish, Charles A. Cravotta Iii, Robin A. Brightbill, Michael J. Langland

United States Geological Survey: Staff Publications

Acidic mine drainage (AMD) from legacy anthracite mines has contaminated Swatara Creek in eastern Pennsylvania. Intermittently collected base-flow data for 1959–1986 indicate that fish were absent immediately downstream from the mined area where pH ranged from 3.5 to 7.2 and concentrations of sulfate, dissolved iron, and dissolved aluminum were as high as 250, 2.0, and 4.7 mg/L, respectively. However, in the 1990s, fish returned to upper Swatara Creek, coinciding with the implementation of AMD treatment (limestone drains, limestone diversion wells, limestone sand, constructed wetlands) in the watershed. During 1996–2006, as many as 25 species of fish were identified in the …

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Recent Advances In Global Lake Coring Hold Promise For Global Change Research In Paleolimnology, Walter E. Dean Jan 2010

Recent Advances In Global Lake Coring Hold Promise For Global Change Research In Paleolimnology, Walter E. Dean

United States Geological Survey: Staff Publications

Thank you, Antje, for your generous comments and I thank IPA for presenting me with this award along with three giants of paleolimnology! I am humbled and delighted to accept this award as a representative of all those in the Paleolimnology community whose creative insights continue to make Paleolimnology inspiring.

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The Influence Of Topology On Hydraulic Conductivity In A Sand-And-Gravel Aquifer, Roger H. Morin, Denis R. Leblanc, Brent M. Troutman Jan 2010

The Influence Of Topology On Hydraulic Conductivity In A Sand-And-Gravel Aquifer, Roger H. Morin, Denis R. Leblanc, Brent M. Troutman

United States Geological Survey: Staff Publications

A field experiment consisting of geophysical logging and tracer testing was conducted in a single well that penetrated a sand-and-gravel aquifer at the U.S. Geological Survey Toxic Substances Hydrology research site on Cape Cod, Massachusetts. Geophysical logs and flowmeter/pumping measurements were obtained to estimate vertical profiles of porosity ϕ, hydraulic conductivity K, temperature, and bulk electrical conductivity under background, freshwater conditions. Saline-tracer fluid was then injected into the well for 2 h and its radial migration into the surrounding deposits was monitored by recording an electromagnetic-induction log every 10 min. The field data are analyzed and interpreted primarily …

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Scale‐Invariant Stress Orientations And Seismicity Rates Near The San Andreas Fault, Amy Day-Lewis, Mark D. Zoback, Stephen Hickman Jan 2010

Scale‐Invariant Stress Orientations And Seismicity Rates Near The San Andreas Fault, Amy Day-Lewis, Mark D. Zoback, Stephen Hickman

United States Geological Survey: Staff Publications

We analyzed measurements of the direction of maximum horizontal compressive stress as a function of depth in two scientific research wells near the San Andreas Fault in central and southern California. We found that the stress orientations exhibit scale‐invariant fluctuations over intervals from tens of cm to several km. Similarity between the scaling of the stress orientation fluctuations and the scaling of earthquake frequency with fault size suggests that these fluctuations are controlled by stress perturbations caused by slip on faults of various sizes in the critically‐stressed crust adjacent to the fault. The apparent difference in stress scaling parameters between …

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The Ties That Bind: Soil Surveyor William Edgar Tharp And Oceanographic Cartographer Marie Tharp, Edward R. Landa Jan 2010

The Ties That Bind: Soil Surveyor William Edgar Tharp And Oceanographic Cartographer Marie Tharp, Edward R. Landa

United States Geological Survey: Staff Publications

The link between soil science and geology is personified in the American father and daughter: soil surveyor William Edgar Tharp (1870–1959) and oceanographic cartographer Marie Tharp (1920–2006). From 1904 to 1935, W.E. Tharp mapped soils in 14 states for the US Department of Agriculture, and campaigned during the late 1920s–early 1930s to raise awareness of the high rates of soil erosion from croplands. The lifestyle of the federal soil surveyor in the United States during the early 20th century involved frequent household moves, and it played a formative role in Marie Tharp’s childhood. Her path to a career in geology …

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Mercury Concentrations In Fish From A Sierra Nevada Foothill Reservoir Located Downstream From Historic Gold-Mining Operations, Michael K. Saiki, Barbara A. Martin, Thomas W. May, Charles N. Alpers Jan 2010

Mercury Concentrations In Fish From A Sierra Nevada Foothill Reservoir Located Downstream From Historic Gold-Mining Operations, Michael K. Saiki, Barbara A. Martin, Thomas W. May, Charles N. Alpers

United States Geological Survey: Staff Publications

This study examined mercury concentrations in whole fish from Camp Far West Reservoir, an 830-ha reservoir in northern California, USA, located downstream from lands mined for gold during and following the Gold Rush of 1848–1864. Total mercury (reported as dry weight concentrations) was highest in spotted bass (mean, 0.93 μg/g; range, 0.16–4.41 μg/g) and lower in bluegill (mean, 0.45 μg/g; range, 0.22– 1.96 μg/g) and threadfin shad (0.44 μg/g; range, 0.21–1.34 μg/g). Spatial patterns for mercury in fish indicated high concentrations upstream in the Bear River arm and generally lower concentrations elsewhere, including downstream near the dam. These findings coincided …

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Microbial Production Of Isotopically Light Iron(Ii) In A Modern Chemically Precipitated Sediment And Implications For Isotopic Variations In Ancient Rocks, G. E. Tangalos, B. L. Beard, C. M. Johnson, Charles N. Alpers, E. S. Shelobolina, H. Xu, H. Konishi, E. E. Roden Jan 2010

Microbial Production Of Isotopically Light Iron(Ii) In A Modern Chemically Precipitated Sediment And Implications For Isotopic Variations In Ancient Rocks, G. E. Tangalos, B. L. Beard, C. M. Johnson, Charles N. Alpers, E. S. Shelobolina, H. Xu, H. Konishi, E. E. Roden

United States Geological Survey: Staff Publications

The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the …

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The Role Of African Dust In The Formation Of Quaternary Soils On Mallorca, Spain And Implications For The Genesis Of Red Mediterranean Soils, Daniel R. Muhs, James Budahn, Anna Avila, Gary Skipp, Joshua Freeman, Deanna Patterson Jan 2010

The Role Of African Dust In The Formation Of Quaternary Soils On Mallorca, Spain And Implications For The Genesis Of Red Mediterranean Soils, Daniel R. Muhs, James Budahn, Anna Avila, Gary Skipp, Joshua Freeman, Deanna Patterson

United States Geological Survey: Staff Publications

African dust additions explain the origin of terra rossa soils that are common on the carbonate-platform island of Mallorca, Spain. Mineralogical and geochemical analyses indicate that Quaternary carbonate eolianites on Mallorca have a very high purity, usually composed of more than 90% carbonate minerals (calcite, dolomite, and aragonite). In contrast, terra rossa soils developed on these eolianites have lower carbonate contents and contain higher concentrations of quartz and other silicates. Analyses of immobile trace elements indicate that the non-carbonate fractions of the eolianites have distinctive Zr/Hf, La/Yb, Cr/Sc and Th/Ta values that differ from the superjacent terra rossa soils. These …

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Assessing The Potential For Luminescence Dating Of Basalts, S. Tsukamoto, G. A.T. Duller, A. G. Wintle, Daniel R. Muhs Jan 2010

Assessing The Potential For Luminescence Dating Of Basalts, S. Tsukamoto, G. A.T. Duller, A. G. Wintle, Daniel R. Muhs

United States Geological Survey: Staff Publications

The possibility of dating basalt using luminescence was tested on four samples with independent age control from Cima volcanic !eld, California, with the ultimate aim of assessing whether the technique could be used to date sediments on the surface of Mars. Previous analysis of these samples had demonstrated that the infrared stimulated luminescence (IRSL) signal is most suitable for dating as it showed the lowest fading rate among various luminescence signals. In this study, changes in equivalent dose as a function of preheat are described. The ages for the two youngest Cima samples agree with the independent ages based on …

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