bluuebunny/crossref_metadata_2025_split huggingface dataset:
Superconductivity of InN with a well defined Fermi surface
Authors: Inushima T. , Kato N. , Maude D. K. , Lu Hai , Schaff W. J. , Tauk R. , Meziani Y. , Ruffenack S. , Briot O. , Knap W. , Gil B. , Miwa H. , Yamamoto A. , Muto D. , Nanishi Y. , Higashiwaki M. , Matsui T. 
Published: June 2006

AbstractIn this report we present our recent investigation on the co‐existence of superconducting and semiconducting properties in InN grown on sapphire (0001) by the use of MBE and MOCVD methods. Magnetotransport measurements were done using InN with a carrier density ne from 4 × 1017 to 4 × 1020 cm–3 in the temperature range from 20 mK to 2 K and under the magnetic field (B) up to 23 T. As a result, even InN samples with ne as low as 4 × 1017 cm–3 showed superconductivity at Tc = 0.12 K. The vortex solid of InN was melted by thermal fluctuation and by the external field, similarly to the observation in layered high Tc superconductors. By the Shubnikov–de Haas oscillation measurements it was found that there were substantial carriers spread in the a–b plane which played an essential role not only for the occurrence of the superconductivity, but also for many other unexpected electronic and optical properties of InN. Based on these results we present a possible mechanism of superconductivity in terms of the interaction between the conduction electrons and the fixed d‐electrons of In atoms spread in the a–b plane. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The dominant shallow 0.225 eV acceptor in GaN
Authors: Monemar B. , Paskov P. P. , Bergman J. P. , Paskova T. , Figge S. , Dennemarck J. , Hommel D. 
Published: June 2006

AbstractWe have studied the optical signatures of the Mg acceptor in GaN, using samples that are doped with Mg during MOCVD growth. In order to reduce the defect density in the material and thus achieve narrow linewidths in optical spectra we have used thick HVPE grown GaN layers as templates in the MOCVD growth. The photoluminescence (PL) spectra show two acceptor‐related bound exciton peaks at 3.466 eV and 3.455 eV respectively. In the lower photon energy range the 3.27 eV emission with its LO‐phonon replicas is dominant, riding on a broad background emission peaking at about 3.1 eV. These results, together with previous data in the literature, indicate that there are two acceptors in Mg‐doped GaN, one dominating the optical spectra (the 3.466 eV and the 3.27 eV emissions) and another related to the 3.455 eV and the 3.1 eV emissions. We suggest that the latter is related to the Mg acceptor, while the former is a H‐related complex, not necessarily involving Mg. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hot carrier energy losses in conducting layers of AlGaN/GaN heterostructures grown on SiC and Al2O3 substrates
Authors: Danilchenko B. A. , Zelensky S. E. , Drok E. , Vitusevich S. A. , Danylyuk S. V. , Klein N. , Lüth H. , Belyaev A. E. , Kochelap V. A. 
Published: June 2006

AbstractThe energy relaxation rate for hot electrons in AlGaN/GaN heterostructures was measured over the temperature range 4.2–300 K. Samples grown on sapphire and 4H‐SiC substrates were studied. The most important result is that the hot carrier energy dissipation differs for samples grown on sapphire and SiC substrates. In the case of sapphire substrate, the dissipation can be described by the emission of optical phonons with an energy of 90 meV and relaxation time of 25 fs. In the case of SiC substrate, both activation energy and relaxation time exceed the values characteristic of the electron‐LO‐phonon dissipation process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural evaluation of GaN/sapphire grown by epitaxial lateral overgrowth by X‐ray microdiffraction
Authors: Drakopoulos M. , Laügt M. , Riemann T. , Beaumont B. , Gibart P. 
Published: June 2006

AbstractThe cover picture from the article [1] depicts the geometry of X‐ray diffraction on a GaN/sapphire structure made by a two‐step epitaxial lateral overgrowth (2S‐ELO) process. Below, the X‐ray rocking curve as a function of the vertical beam position in 2S‐ELO GaN/sapphire is shown. A low intensity line diverging from the main peak position (arrow) may be interpreted as the disappearance of a winged crystal region due to dislocation curvature.This paper is a presentation from the 6th International Conference on Nitride Semiconductors held in Bremen, Germany, in 2005. Further articles from ICNS‐6 are also being published in phys. stat. sol. (a) 203, No. 7 (2006) and phys. stat. sol. (c) 3, No. 6 (2006).
UPLC/MSE; a new approach for generating molecular fragment information for biomarker structure elucidation
Authors: Plumb Robert S. , Johnson Kelly A. , Rainville Paul , Smith Brian W. , Wilson Ian D. , Castro‐Perez Jose M. , Nicholson Jeremy K. 
Published: June 2006

AbstractA new approach to obtain fragmentation information in liquid chromatography/mass spectrometry (LC/MS) studies of small molecules in complex mixtures is presented using simultaneous acquisition of exact mass at high and low collision energy, MSE. LC/MS‐TOF and LC/MS/MS‐TOF are powerful tools for the analysis of complex mixtures, especially those for biological fluids allowing the elucidation of elemental composition and fragmentation information. In this example the composition of rat urine was studied using this new approach, allowing the structures of several endogenous components to be confirmed in one analytical run by the simultaneous acquisition of exact mass precursor and fragment ion data. The spectral data obtained using this new approach are comparable to those obtained by conventional LC/MS/MS as exemplified by the identification of endogenous metabolites present in rat urine. Copyright © 2006 John Wiley & Sons, Ltd.
Characterization of nodularin variants in Nodularia spumigena from the Baltic Sea using liquid chromatography/mass spectrometry/mass spectrometry
Authors: Mazur‐Marzec Hanna , Meriluoto Jussi , Pliński Marcin , Szafranek Janusz 
Published: June 2006

AbstractNodularin is a potent hepatotoxic cyclic pentapeptide produced by planktonic cyanobacterium Nodularia spumigena. Bloom and culture samples of the cyanobacterium collected and isolated from the Gulf of Gdańsk, southern Baltic Sea, were analyzed. Hybrid quadrupole‐time‐of‐flight liquid chromatography/mass spectrometry/mass spectrometry (TOF‐LC/MS/MS) with ionspray (ISP) and collision‐induced dissociation (CID) were used to characterize nodularin and its analogues. The identification process was based on the comparison of recorded product ion spectra with the previously reported FAB‐MS/CID (high‐energy) mass spectra of the corresponding nodularin variants. Amino acid structures and sequences were derived from the fragmentation pattern of the [M+H]+ ions. Apart from unmodified nodularin with an arginine residue (NOD‐R), three demethylated variants have been found. The sites of demethylation were located on aspartic acid [Asp1]NOD, the Adda residue [DMAdda3]NOD, and dehydrobutyric acid [dhb5]NOD. In two other nodularin variants an additional methyl group is located in the Adda [MeAdda]NOD and Glu [Glu4(OMe)]NOD residues. The linear NOD and the geometrical isomer of NOD‐R, reported earlier in N. spumigena from New Zealand, have also been detected. Two of the total eight nodularin variants characterized in the present study, [dhb5]NOD and [MeAdda]NOD, have not been described earlier. Copyright © 2006 John Wiley & Sons, Ltd.
Flushing time and storage effects on the accuracy and precision of carbon and oxygen isotope ratios of sample using the Gasbench II technique
Authors: Paul Debajyoti , Skrzypek Grzegorz 
Published: June 2006

AbstractContinuous‐flow isotope ratio mass spectrometry interfaced with a Gasbench II is used for automated and faster analyses of δ13C and δ18O in water, carbonate, and air samples that are accurate and highly precise. Prior to online chemistry and measurement using the Gasbench technique, rubber septa‐capped glass vials are routinely flushed to remove air. Due to the small amounts of sample gas required for isotope analyses using current techniques, care should be taken to properly flush these vials to avoid contamination of sample gas with air. Our results indicate that isotopic composition of sample CO2 gas remains constant when 10 mL vials are flushed (rate of 100 mL/min) for ≥600 s, whereas for vials flushed <600 s, the isotopic composition becomes substantially lighter with decreasing time of flushing, which affects the accuracy of analyses. This largely depends on the isotopic composition (and volume) of air that still remains after flushing. This effect is more pronounced on δ18O than on δ13C of sample CO2 gas because there is very little carbon in the air. After 24 h storage in vials with punctured septa, both δ13C and δ18O of CO2 become isotopically heavier compared with first day analyses, suggesting time‐dependent changes in isotopic composition. The magnitude of shift depends on the concentration and the isotopic composition of CO2 in laboratory air as well as on fractionation due to outflow of sample gas or inflow of air via punctured septa. Contamination of sample gas with air can be observed as a secondary peak on chromatograms that precedes sample peaks, and the intensity of these peaks depends on the amount of air. Such peaks are always present with short flushing times. For accuracy and better precision, irrespective of the magnitude of the secondary peaks, the analyses should be discarded if these appear in the chromatograms. Copyright © 2006 John Wiley & Sons, Ltd.
Contributions of common sources of polycyclic aromatic hydrocarbons to soil contamination
Authors: Simon John A. , Sobieraj James A. 
Published: June 2006

AbstractAsphalt products, particularly sealants, are prepared using petroleum products that contain a com‐plex mixture of aliphatic and aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs). Clearly, these products are ubiquitous in urban environments, which raises an issue regard‐ing the potential for PAHs to be transported from parking lots to underlying or adjacent soil, surface‐water bodies, or groundwater. Based on a literature review, there are limited studies focus‐ing on this issue; however, the studies that have been published have fascinating conclusions. The literature shows, as expected, that asphalt‐based products contain PAHs. The highest PAH concen‐trations are present in asphalt sealants, particularly those manufactured using coal tar. Furthermore, due to the low solubility and high partition coefficients of PAHs, the potential for PAHs to leach from asphalt surfaces is negligible, which has been confirmed by leachability studies. Thus, there is little risk that PAHs will be present in stormwater runoff or leach into groundwater from asphalt‐paved areas in a dissolved form. However, asphalt pavement and sealants produce particulate matter that can contain concentrations of PAHs in the sub‐percent range (100s to 1,000s mg/kg total PAHs) that is transported in stormwater runoff. Some studies show that this can cause soil and sediment con‐tamination with total PAH concentrations in the range of 1 to 10 mg/kg. From a remediation per‐spective, many site cleanups are conducted to remediate the presence of PAHs to cleanup goals below 1 mg/kg or, in some cases, 0.1 mg/kg or lower. From a total risk perspective, remediating sites to low PAH cleanup goals may be unwarranted in light of the risk of transportable PAHs produced from paved parking surfaces. In other words, is it reasonable to conduct a cleanup to remediate low PAH concentrations and then redevelop the area with asphalt pavement and sealant, which may pose a greater PAH‐related risk? © 2006 Wiley Periodicals, Inc.
Environmental cleanup of the nation's former nuclear weapons sites: Unprecedented public‐private challenges at the largest facilities
Authors: Mayer Henry , Faass Josephine , Greenberg Michael R. , Lewis David 
Published: June 2006

AbstractIn 1994, the U.S. Department of Energy (DOE) initiated a contract reform program intended to strengthen oversight capabilities and encourage the creation of contract and incentive structures, which would effectively facilitate the treatment of onsite contamination and waste. The remedia‐tion and disposal of these legacy wastes is the core of the Department's environmental manage‐ment mission (Government Accountability Office [GAO], 2003). Despite a concerted effort toward achieving the goals of the reform, progress has been slow. Many projects continue to necessitate cost and time extensions above those originally agreed upon. Although the Department insti‐tuted an accelerated cleanup program in 2002, promising to shave some $50 billion and 35 years from its earlier cost and schedule projections, there have been delays in critical project areas that call into question the attainability of the proposed reductions (GAO, 2005). Numerous explana‐tions have been offered as to why achieving these goals has proven so difficult, many of which have concluded that flawed contracting practices are to blame. This article concludes that the root of the problem is much deeper and that the organizational criticisms aimed at DOE are as much a legacy as the waste itself. Although the focus of this article is on large former nuclear weapons sites, these types of contracting and organizational issues are often found at other gov‐ernment and private complex hazardous waste sites. © 2006 Wiley Periodicals, Inc.
Enhanced anaerobic bioremediation of chlorinated solvents utilizing vegetable oil emulsions
Authors: Newman William A. , Pelle Ronald C. 
Published: June 2006

AbstractThe use of vegetable oil as an electron donor to enhance the reductive dechlorination of chlori‐nated solvents as an in situ remediation technology is gaining significant traction. Vegetable oil is a cost‐effective slow‐release electron donor with greater hydrogen‐release efficiency than other electron‐donor products. However, neat vegetable oil can inhibit distribution in aquifers due to the oil droplets blocking the flow of groundwater through the smaller pore spaces in the aquifer materials. This issue has been partially overcome by applying the vegetable oil as an oil‐water emulsion, which typically is created in the field. However, the field preparation results in a mixture of droplet sizes, including larger droplets that can make the emulsions unstable and reduce the soil permeability by blocking soil‐pore throats with oil. RNAS, Inc., has developed a kinetically sta‐ble soybean oil emulsion (“Newman Zone”) consisting of submicron droplets with less droplet‐size variation than field‐prepared emulsions. This product is composed of a blend of fast‐release (sodium lactate) and slow‐release (soybean oil) electron donors. The emulsion is produced in a stable factory environment in which it is pasteurized and packaged in sterile packaging. This ma‐terial can be utilized as an electron donor without further treatments or amendments in the field. This article discusses factors associated with selecting electron donors and the development of vegetable oil–based products. A case study of an application of Newman Zone at a former adhe‐sives manufacturing facility is then presented. The case study demonstrates the effect of Newman Zone in reducing chlorinated solvent concentrations in groundwater by both rapidly stimulating initial microbial activity and supporting long‐term reductive dechlorination with a slow‐release electron donor. © 2006 Wiley Periodicals, Inc.
Nitrogen dynamics in sediment during water level manipulation on the Upper Mississippi River
Authors: Cavanaugh Jennifer C. , Richardson William B. , Strauss Eric A. , Bartsch Lynn A. 
Published: June 2006

AbstractNitrogen (N) has been linked to increasing eutrophication in the Gulf of Mexico and as a result there is increased interest in managing and improving water quality in the Mississippi River system. Water level reductions, or ‘drawdowns’, are being used more frequently in large river impoundments to improve vegetation growth and sediment compaction. We selected two areas of the Upper Mississippi River system (Navigation Pool 8 and Swan Lake) to examine the effects of water level drawdown on N dynamics. Navigation Pool 8 experienced summer drawdowns in 2001 and 2002. Certain areas of Swan Lake have been drawn down annually since the early 1970s where as other areas have remained inundated. In the 2002 Pool 8 study we determined the effects of sediment drying and rewetting resulting from water level drawdown on (1) patterns of sediment nitrification and denitrification and (2) concentrations of sediment and surface water total N (TN), nitrate, and ammonium (NH). In 2001, we only examined sediment NH and TN. In the Swan Lake study, we determined the long‐term effects of water level drawdowns on concentrations of sediment NH and TN in sediments that dried annually and those that remained inundated. Sediment NH decreased significantly in the Pool 8 studies during periods of desiccation, although there were no consistent trends in nitrification and denitrification or a reduction in total sediment N. Ammonium in sediments that have dried annually in Swan Lake appeared lower but was not significantly different from sediments that remain wet. The reduction in sediment NH in parts of Pool 8 was likely a result of increased plant growth and N assimilation, which is then redeposited back to the sediment surface upon plant senescence. Similarly, the Swan Lake study suggested that drawdowns do not result in long term reduction in sediment N. Water level drawdowns may actually reduce water retention time and river‐floodplain connectivity, while promoting significant accumulation of organic N. These results indicate that water level drawdowns are probably not an effective means of removing N from the Upper Mississippi River system. Copyright © 2006 John Wiley & Sons, Ltd.
Inter‐habitat variation in the benthos of the Upper Missouri River (North Dakota, USA): implications for Great River bioassessment
Authors: Angradi Ted R. , Schweiger E. William , Bolgrien David W. 
Published: June 2006

AbstractWe examined inter‐habitat variation in benthic macroinvertebrate assemblages in the 180‐km Garrison Reach of the Upper Missouri River, North Dakota (USA) in 2001–2003. The Garrison Reach is unchannelized with a mostly rural setting. Flows are regulated by Garrison Dam. We sampled benthos from three habitats defined a priori: channel, shoreline, and backwater. Benthic assemblages were different in each habitat. Average Bray‐Curtis dissimilarity in assemblage composition ranged from 89% for backwater versus channel habitat to 70% for backwater versus shoreline habitat. There were distinct intra‐habitat groups within a priori habitats: channel assemblages included moving‐sand assemblages and other‐substrate channel assemblages; backwater assemblages included connected (to the river channel) and unconnected backwater assemblages; shorelines assemblages varied between natural (unprotected) and riprap (rock revetment) shorelines. Abundance and taxa richness were lowest and spatial variability highest for moving‐sand channel assemblages. Abundance was highest in backwaters. Taxa richness in backwaters and along channel shorelines were similar. Assemblages in all three habitats were dominated by Nematoda, Oligochaeta and Chironomidae. Taxa in these groups comprised at least 80% of mean abundance in all three habitats. Taxa that discriminated among habitats included the psammophilic chironomid Chernovskiia for moving‐sand channel substrates versus all other habitats; Hydroptila (Trichoptera) for riprap vs natural shorelines, Aulodrilus (Oligochaeta) for connected versus unconnected backwaters; and Nematoda for backwater versus channel and shoreline versus channel. Based on overlap patterns in benthic assemblages among habitats, we concluded that sampling main channel shorelines should also capture much of the natural and stressor‐induced variation in connected backwater and channel habitat exclusive of moving‐sand channel habitat. Published in 2006 by John Wiley & Sons, Ltd.
Influences of environmental conditions on macrophyte communities in drought‐affected headwater streams
Authors: Westwood C. G. , Teeuw R. M. , Wade P. M. , Holmes N. T. H. , Guyard P. 
Published: June 2006

AbstractA 10‐year study of groundwater‐dominated headwater streams in the chalklands of southern England has highlighted the major influence that stream flow has on the composition of in‐channel macrophyte communities. Macrophytes supply much of the physical structure within these headwater channels, as well as providing habitats for a rich assemblage of higher life forms, some of them specialized and rare. The overall influence of stream flow however, is modulated by many environmental factors operating at diverse spatial scales. Data describing the relevant environmental variables were accumulated for six chalk streams in the Thames basin and related directly to the vegetation record by means of Canonical Correspondence Analysis, correlation tests and other analyses, to reveal the circumstances in which communities would be likely to thrive and those in which they would be negatively impacted by variations in stream flow. It was found that local topography and channel dimensions had a direct influence on the composition of communities at local level and that land use and rates of water abstraction had an underlying, but no less important, influence at catchment level. The species most associated with positive species diversity were those of sluggish flow and damp margins indicating the importance of velocity and moisture gradients across the channel in producing a full manifestation of the flora. Strong negative correlations were produced by non‐aquatic grasses and herbs, which represent prolonged periods of channel desiccation. The environmental parameters most associated with positive diversity were high local water stages, wide channels and a high degree of semi‐natural land use within the catchment. Steep channel gradients were strongly associated with negative diversity. The results have confirmed that optimal channel conditions, as exemplified by the classic ‘winterbourne’ with its low‐flow channel, extensive margins, gently sloping banks and high seasonal inundation, will produce good conditions for species diversity and make communities more resistant to the effects of drought. These conditions can be enhanced through sensitive catchment management that encourages rainfall percolation, limits abstractions and seeks to maintain a low intensity of landcover management. Copyright © 2006 John Wiley & Sons, Ltd.