bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas Turbine Cycles With Solid Oxide Fuel Cells—Part II: A Detailed Study of a Gas Turbine Cycle With an Integrated Internal Reforming Solid Oxide Fuel Cell
Authors: Harvey S. P. , Richter H. J.
Published: April 2008

In conventional energy conversion processes, the fuel combustion is usually highly irreversible, and is thus responsible for the low overall efficiency of the power generation process. The energy conversion efficiency can be improved if immediate contact of air and fuel is prevented. One means to prevent this immediate contact is the use of fuel cell technology. Significant research is currently being undertaken to develop fuel cells for large-scale power production. High-temperature solid oxide fuel cells (SOFC) have many features that make them attractive for utility and industrial applications. However, in view of their high operating temperatures and the incomplete nature of the fuel oxidation process, such fuel cells must be combined with conventional power generation technology to develop power plant configurations that are both functional and efficient. Most fuel cell cycles proposed in the literature use a high-temperature fuel cell running at ambient pressure and a steam bottoming cycle to recover the waste heat generated by the fuel cell. With such cycles, the inherent flexibility and shorter start-up time characteristics of the fuel cell are lost. In Part I of this paper (Harvey and Richter, 1994), a pressurized cycle using a solid oxide fuel cell and an integrated gas turbine bottoming cycle was presented. The cycle is simpler than most cycles with steam bottoming cycles and more suited to flexible power generation. In this paper, we will discuss this cycle in more detail, with an in-depth discussion of all cycle component characteristics and losses. In particular, we will make use of the fuel cell’s internal fuel reforming capability. The optimal cycle parameters were obtained based on calculations performed using Aspen Technology’s ASPEN PLUS process simulation software and a fuel cell simulator developed by Argonne National Laboratory (Ahmed et al., 1991). The efficiency of the proposed cycle is 68.1 percent. A preliminary economic assessment of the cycle shows that it should compare favorably with a state-of-the-art combined cycle plant on a cost per MWe basis.
Combined x-ray photoelectron spectroscopy/ultraviolet photoelectron spectroscopy/field emission spectroscopy for characterization of electron-emission mechanism of diamond
Authors: Yamaguchi H. , Kudo Y. , Masuzawa T. , Kudo M. , Yamada T. , Takakuwa Y. , Okano K.
Published: April 2008

A possible mechanism for the field emission spectroscopy (FES) peak energy shift observed for lightly nitrogen (N)-doped chemical vapor deposition (CVD) diamond was investigated using natural IIb diamond as a reference. Combined ultraviolet photoelectron spectroscopy/FES spectra of natural IIb diamond indicated that the origin of field-emitted electrons is at the valence-band maximum and does not shift depending on the applied voltages. To further investigate the mechanism, FES peak energy was plotted versus emission current and the plot was best fitted to a straight line. The resistance of the diamond obtained from the slope was 109Ω and almost 0 for natural IIb diamond and lightly N-doped CVD diamond, respectively. The result was confirmed to be consistent with the resistivity of lightly N-doped CVD diamond and natural IIb diamond. Therefore, the result strongly implies that the observed energy shift is due to the voltage drop at the field emission site due to the resistance of the diamond bulk. Details of a possible mechanism are explained.
Optical and electrical properties of amorphous zinc tin oxide thin films examined for thin film transistor application
Authors: Jayaraj Madambi K. , Saji Kachirayil J. , Nomura Kenji , Kamiya Toshio , Hosono Hideo
Published: April 2008

Structural, electronic, and optical properties of amorphous and transparent zinc tin oxide films deposited on glass substrates by pulsed laser deposition (PLD) were examined for two chemical compositions of Zn:Sn=1:1 and 2:1 as a function of oxygen partial pressure (PO2) used for the film deposition and annealing temperature. Different from a previous report on sputter-deposited films [Chiang et al., Appl. Phys. Lett. 86, 013503 (2005)], the PLD-deposited films crystallized at a lower temperature <450 °C to give crystalline ZnO and SnO2 phases. The optical band gaps (Tauc gaps) were 2.80−2.85 eV and almost independent of oxygen PO2, which are smaller than those of the corresponding crystals (3.35−3.89 eV). Films deposited at low PO2 showed significant subgap absorptions, which were reduced by postthermal annealing. Hall mobility showed steep increases when carrier concentration exceeded threshold values and the threshold value depended on the film chemical composition. The films deposited at low PO2<2 Pa had low carrier concentrations. It is thought that the low PO2 produced high-density oxygen deficiencies and generated electrons, but these electrons were trapped in localized states, which would be observed as the subgap absorptions. Similar effects were observed for 600 °C crystallized films and their resistivities were increased by formation of subgap states due to the reducing high-temperature condition. High carrier concentrations and large mobilities were obtained in an intermediate PO2 region for the as-deposited films.
Electrical biasing and time dependent evolution of defects in poly(triphenylamine)-butane vinyl organic semiconductor devices
Authors: Devine R. A. B. , Wang Fei , Rauh R. D.
Published: April 2008

Field effect transistors based upon the organic semiconductor poly(triphenylamine)-butane vinyl have been characterized. The carrier mobility is observed to vary significantly with time immediately after manufacture of the devices but to become very stable after extended periods (>1month). The stabilized, carrier mobility is estimated to be ∼6×10−5cm2V−1s−1 from saturation source-drain current measurements. Repeated measurements of source-drain currents as a function of gate electrode potential evidence the presence of positive charge trapping at defects in the semiconductor layer during the measurement leading to uncertainty in mobility and threshold voltage determination. Constant bias stressing at −2MVcm−1 results in a decrease in the carrier mobility and an increasingly negative threshold voltage shift consistent with positive charge trapping. Following the removal of the stressing field, the mobility increases back to its prestress value and the threshold voltage shift decreases. From these data, a crude estimate of the trap depth is estimated to be 0.7–0.8eV. An anomalous channel length dependence of the carrier mobility is determined from source-drain saturation current as a function of gate-source voltage measurements.
Defects in CdHgTe grown by molecular beam epitaxy on (211)B-oriented CdZnTe substrates
Authors: Selvig E. , Tonheim C. R. , Kongshaug K. O. , Skauli T. , Hemmen H. , Lorentzen T. , Haakenaasen R.
Published: April 2008

A systematic study of the evolution of the defect morphology and crystalline quality in molecular beam epitaxially grown CdxHg1−xTe epilayers with growth temperature is presented. The layers were characterized with optical microscopy, atomic force microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and high-resolution x-ray diffraction. Four types of defects (microvoids, hillocks, high-temperature voids, and needles) were characterized on epilayers grown in the growth temperature range 188.9−209.9 °C. There is a minimum in the area covered by defects at a temperature just below the onset of Te precipitation, which is defined as the optimal growth temperature. Microvoids with various shapes, and at various stages of growth, were observed side-by-side in many of the CdxHg1−xTe layers, along with hillocks and needles. The defect density of microvoids changes by several orders of magnitude in the studied temperature range. A mechanism for the formation of microvoids and needles is suggested. High-temperature voids associated with Te precipitates appear above the optimal growth temperature. The onset of Te precipitation is well described by a thermodynamic model.
Indium-doped ZnO nanospirals synthesized by thermal evaporation
Authors: Gao Hong , Ji Hong , Zhang Xitian , Lu Huiqing , Liang Yao
Published: April 2008

Indium-doped ZnO nanospirals were synthesized by one-step thermal evaporation. Transmission electron micrographs show that the nanospirals are structurally uniform and free of defects. The helical nanostructures, which are constructed by rolling nanobelts grown along the ⟨101¯0⟩ direction with the ±(0001) polar planes as the dominate surfaces, are energetically favored in terms of the electrostatic polar charge model. The typical radius of curvature of the nanospirals is several micrometers. The In-doped nanospirals are expected to have interesting optoelectronic and mechanical properties and could be potential building blocks in nanoscale optoelectronic and electromechanical systems.
Enhanced growth of anodic alumina nanochannels on Ga-ion pre-irradiated aluminum
Authors: Liu C. Y. , Datta A. , Liu N. W. , Wu Y. R. , Wang H. H. , Chuang T. H. , Wang Y. L.
Published: April 2008

Exposure of an Al substrate to energetic Ga ions is found to result in enhanced growth rate of its nanochannels during a subsequent anodization process. Depending on the ion dose, the nanochannels in the pre-irradiated area exhibit different lengths. This interesting phenomenon is exploited by scanning a Ga focused ion beam over the desired area to facilitate the fabrication of arrays of anodic alumina nanochannels with custom-designed super-structure, which is based on the variation of channel length in different areas.
Three-dimensional metal patterning over nanostructures by reversal imprint
Authors: Peng C. , Cardozo B. L. , Pang S. W.
Published: April 2008

Reversal imprint is used to pattern three-dimensional (3D) metal structures over substrates with complex topography. Metal films are deposited onto SU-8 polymer layers on glass molds, lithographically patterned, and transferred to Si or SU-8 substrates with nanosctructured surfaces by reversal imprint at 5MPa, 80°C, and 1s of UV exposure. The transfer of metal patterns of 50∕20nm thick Au∕Ti and 0.5μm thick Al as well as 3D Al structures have been demonstrated.
Electron-emission properties of silicon field-emitter arrays in gaseous ambient for charge-compensation device
Authors: Takeuchi Mitsuaki , Kojima Toshihiko , Oowada Atsushi , Gotoh Yasuhito , Nagao Masayoshi , Tsuji Hiroshi , Ishikawa Junzo , Sakai Sigeki , Kimoto Tsunenobu
Published: April 2008

Electron-emission properties of silicon field-emitter arrays treated with trifluoromethane plasma (Si:C-FEA) were evaluated under H2, CH4, CO, CO2, O2, and C2H4 ambients. Oxidizing gases, including O2 and CO2, make shortened the lifetime. However, reductive gases such as H2 and CH4 lengthened the lifetime longer. On the other hand, C2H4 caused a decrease of the emission current, despite the fact that C2H4 is considered to be one of the reductive gases. Furthermore, emission properties can be recovered by the aging process in an ultrahigh vacuum. This is probably attributable to physisorption and desorption of C2H4 molecules or decomposed molecules onto the emitter surface of the Si:C-FEA.
Synthesis of epitaxial silicon nanowires on Si(111) substrates using ultrahigh vacuum magnetron sputtering
Authors: Zhao X. W. , Yang F. Y.
Published: April 2008

Epitaxial silicon nanowires on Si(111) surface and nonepitaxial silicon nanowires on thermally oxidized silicon substrates have been synthesized using ultrahigh vacuum sputtering. Silicon nanowires with noncylindrical shape and diameter of 200–300nm were obtained on thermally oxidized Si substrates using Au(15Å)∕Si(8Å)∕Au(15Å) trilayer as catalysts. Cylindrical silicon nanowires with diameter between 40 and 100nm and length up to 8μm were synthesized using epitaxial growth on Si(111) substrates. Sputter provides an alternative fabrication technique for silicon nanowire synthesis in ultrahigh vacuum environment.
Effect of growth temperature on InGaSb metamorphic layers and the fabrication of InGaSb p-i-n diodes
Authors: Mohammedy F. M. , Hulko O. , Robinson B. J. , Thompson D. A. , Deen M. J.
Published: April 2008

Metamorphic growth of In0.15Ga0.85Sb on a GaSb substrate is reported using InxGa1−xSb buffer layers compositionally graded in steps of x=0.03. All layers were grown using gas source molecular beam epitaxy with a fixed Sb flux providing an excess group-V overpressure. The growth temperature was varied from 450to540°C. X-ray diffraction analysis was used to determine the effect of growth temperature on relaxation and residual strain. As the growth temperature is increased, cross-sectional transmission electron microscopy (TEM) shows that the number of dislocations threading through the metamorphic layer are reduced. Plan-view TEM yields misfit dislocation density around 108cm−2 and from atomic force microscopy, the surface roughness is ∼1nm. Both surface roughness and dislocation density improves with higher growth temperature. Finally, p-i-n homojunction diodes of various sizes on metamorphic layers were demonstrated.
The Antidepressant Fluoxetine Restores Plasticity in the Adult Visual Cortex
Authors: Vetencourt José Fernando Maya , Sale Alessandro , Viegi Alessandro , Baroncelli Laura , De Pasquale Roberto , F. O'Leary Olivia , Castrén Eero , Maffei Lamberto
Published: April 2008

We investigated whether fluoxetine, a widely prescribed medication for treatment of depression, restores neuronal plasticity in the adult visual system of the rat. We found that chronic administration of fluoxetine reinstates ocular dominance plasticity in adulthood and promotes the recovery of visual functions in adult amblyopic animals, as tested electrophysiologically and behaviorally. These effects were accompanied by reduced intracortical inhibition and increased expression of brain-derived neurotrophic factor in the visual cortex. Cortical administration of diazepam prevented the effects induced by fluoxetine, indicating that the reduction of intracortical inhibition promotes visual cortical plasticity in the adult. Our results suggest a potential clinical application for fluoxetine in amblyopia as well as new mechanisms for the therapeutic effects of antidepressants and for the pathophysiology of mood disorders.
Phytoplankton Calcification in a High-CO
2
World
Authors: Iglesias-Rodriguez M. Debora , Halloran Paul R. , Rickaby Rosalind E. M. , Hall Ian R. , Colmenero-Hidalgo Elena , Gittins John R. , Green Darryl R. H. , Tyrrell Toby , Gibbs Samantha J. , von Dassow Peter , Rehm Eric , Armbrust E. Virginia , Boessenkool Karin P.
Published: April 2008

Ocean acidification in response to rising atmospheric CO
2
partial pressures is widely expected to reduce calcification by marine organisms. From the mid-Mesozoic, coccolithophores have been major calcium carbonate producers in the world's oceans, today accounting for about a third of the total marine CaCO
3
production. Here, we present laboratory evidence that calcification and net primary production in the coccolithophore species
Emiliania huxleyi
are significantly increased by high CO
2
partial pressures. Field evidence from the deep ocean is consistent with these laboratory conclusions, indicating that over the past 220 years there has been a 40% increase in average coccolith mass. Our findings show that coccolithophores are already responding and will probably continue to respond to rising atmospheric CO
2
partial pressures, which has important implications for biogeochemical modeling of future oceans and climate.
Atomlike, Hollow-Core–Bound Molecular Orbitals of C
60
Authors: Feng Min , Zhao Jin , Petek Hrvoje
Published: April 2008

The atomic electron orbitals that underlie molecular bonding originate from the central Coulomb potential of the atomic core. We used scanning tunneling microscopy and density functional theory to explore the relation between the nearly spherical shape and unoccupied electronic structure of buckminsterfullerene (C
60
) molecules adsorbed on copper surfaces. Besides the known π* antibonding molecular orbitals of the carbon-atom framework, above 3.5 electron volts we found atomlike orbitals bound to the core of the hollow C
60
cage. These “superatom” states hybridize like the s and p orbitals of hydrogen and alkali atoms into diatomic molecule-like dimers and free-electron bands of one-dimensional wires and two-dimensional quantum wells in C
60
aggregates. We attribute the superatom states to the central potential binding an electron to its screening charge, a property expected for hollow-shell molecules derived from layered materials.
Kaposi's Sarcoma-Associated Herpesvirus-Encoded LANA Can Interact with the Nuclear Mitotic Apparatus Protein To Regulate Genome Maintenance and Segregation
Authors: Si Huaxin , Verma Subhash C. , Lampson Michael A. , Cai Qiliang , Robertson Erle S.
Published: April 2008

Kaposi's sarcoma-associated herpesvirus (KSHV) genomes are tethered to the host chromosomes and partitioned faithfully into daughter cells with the host chromosomes. The latency-associated nuclear antigen (LANA) is important for segregation of the newly synthesized viral genomes to the daughter nuclei. Here, we report that the nuclear mitotic apparatus protein (NuMA) and LANA can associate in KSHV-infected cells. In synchronized cells, NuMA and LANA are colocalized in interphase cells and separate during mitosis at the beginning of prophase, reassociating again at the end of telophase and cytokinesis. Silencing of NuMA expression by small interfering RNA and expression of LGN and a dominant-negative of dynactin (P150-CC1), which disrupts the association of NuMA with microtubules, resulted in the loss of KSHV terminal-repeat plasmids containing the major latent origin. Thus, NuMA is required for persistence of the KSHV episomes in daughter cells. This interaction between NuMA and LANA is critical for segregation and maintenance of the KSHV episomes through a temporally controlled mechanism of binding and release during specific phases of mitosis.
Amino Acids 143 to 150 of the Herpes Simplex Virus Type 1 Scaffold Protein Are Required for the Formation of Portal-Containing Capsids
Authors: Huffman Jamie B. , Newcomb William W. , Brown Jay C. , Homa Fred L.
Published: April 2008

The herpes simplex virus type 1 (HSV-1) portal is composed of a dodecamer of UL6 protein molecules whose incorporation into the capsid is mediated by interaction with the HSV-1 UL26.5 scaffold protein. Previous results with an in vitro capsid assembly assay demonstrated that nine amino acids (amino acids 143 to 151) of the UL26.5 protein are required for its interaction with UL6 and for incorporation of the portal complex into capsids. In the present study an HSV-1 mutant, bvFH411, was isolated and contained a deletion that removed the codons for UL26.5 amino acids 143 to 150. The mutant virus failed to produce infectious virus in noncomplementing cells, and only B capsids that contained only minor amounts of portal protein were made. These data corroborate our previous in vitro studies and demonstrate that amino acids 143 to 150 of UL26.5 are required for the formation of portal-containing HSV-1 capsids.
Sulfatide Is Required for Efficient Replication of Influenza A Virus
Authors: Takahashi Tadanobu , Murakami Kouki , Nagakura Momoe , Kishita Hideyuki , Watanabe Shinya , Honke Koichi , Ogura Kiyoshi , Tai Tadashi , Kawasaki Kazunori , Miyamoto Daisei , Hidari Kazuya I. P. J. , Guo Chao-Tan , Suzuki Yasuo , Suzuki Takashi
Published: April 2008

Sulfatide is abundantly expressed in various mammalian organs, including the intestines and trachea, in which influenza A viruses (IAVs) replicate. However, the function of sulfatide in IAV infection remains unknown. Sulfatide is synthesized by two transferases, ceramide galactosyltransferase (CGT) and cerebroside sulfotransferase (CST), and is degraded by arylsulfatase A (ASA). In this study, we demonstrated that sulfatide enhanced IAV replication through efficient translocation of the newly synthesized IAV nucleoprotein (NP) from the nucleus to the cytoplasm, by using genetically produced cells in which sulfatide expression was down-regulated by RNA interference againstCSTmRNA or overexpression of theASAgene and in which sulfatide expression was up-regulated by overexpression of both theCSTandCGTgenes. Treatment of IAV-infected cells with an antisulfatide monoclonal antibody (MAb) or an anti-hemagglutinin (HA) MAb, which blocks the binding of IAV and sulfatide, resulted in a significant reduction in IAV replication and accumulation of the viral NP in the nucleus. Furthermore, antisulfatide MAb protected mice against lethal challenge with pathogenic influenza A/WSN/33 (H1N1) virus. These results indicate that association of sulfatide with HA delivered to the cell surface induces translocation of the newly synthesized IAV ribonucleoprotein complexes from the nucleus to the cytoplasm. Our findings provide new insights into IAV replication and suggest new therapeutic strategies.
A New Role for ns Polyprotein Cleavage in Sindbis Virus Replication
Authors: Gorchakov Rodion , Frolova Elena , Sawicki Stanley , Atasheva Svetlana , Sawicki Dorothea , Frolov Ilya
Published: April 2008

One of the distinguishing features of the alphaviruses is a sequential processing of the nonstructural polyproteins P1234 and P123. In the early stages of the infection, the complex of P123+nsP4 forms the primary replication complexes (RCs) that function in negative-strand RNA synthesis. The following processing steps make nsP1+P23+nsP4, and later nsP1+nsP2+nsP3+nsP4. The latter mature complex is active in positive-strand RNA synthesis but can no longer produce negative strands. However, the regulation of negative- and positive-strand RNA synthesis apparently is not the only function of ns polyprotein processing. In this study, we developed Sindbis virus mutants that were incapable of either P23 or P123 cleavage. Both mutants replicated in BHK-21 cells to levels comparable to those of the cleavage-competent virus. They continuously produced negative-strand RNA, but its synthesis was blocked by the translation inhibitor cycloheximide. Thus, after negative-strand synthesis, the ns proteins appeared to irreversibly change conformation and formed mature RCs, in spite of the lack of ns polyprotein cleavage. However, in the cells having no defects in α/β interferon (IFN-α/β) production and signaling, the cleavage-deficient viruses induced a high level of type I IFN and were incapable of causing the spread of infection. Moreover, the P123-cleavage-deficient virus was readily eliminated, even from the already infected cells. We speculate that this inability of the viruses with unprocessed polyprotein to productively replicate in the IFN-competent cells and in the cells of mosquito origin was an additional, important factor in ns polyprotein cleavage development. In the case of the Old World alphaviruses, it leads to the release of nsP2 protein, which plays a critical role in inhibiting the cellular antiviral response.
The impact of components of fine particulate matter on cardiovascular mortality in susceptible subpopulations
Authors: Ostro B D , Feng W-Y , Broadwin R , Malig B J , Green R S , Lipsett M J
Published: April 2008

Background:

Several studies have demonstrated associations between daily mortality and ambient particulate matter less than 2.5 microns in diameter (fine particles or PM2.5). Few, however, have examined the relative toxicities of PM2.5 constituents, including elemental carbon and organic carbon (EC and OC, respectively), nitrates and transition metals. There is also little information about whether associations between PM2.5 constituents and mortality are modified by socioeconomic and demographic factors.

Aim:

To examine associations of daily cardiovascular mortality with PM2.5 and its constituents after stratification by gender, race/ethnicity and education, using data from six California counties during 2000 to 2003.

Methods:

The association of daily counts of cardiovascular mortality with PM2.5 components was analysed using time-series regression analyses. Poisson models with natural splines were used to control for time-varying covariates such as season and weather. Separate models were run after stratification by gender, race/ethnicity (White, Hispanic, Black) and education (high school graduation or not). Models were run for each county and results were combined using random effects meta-analysis.

Results:

Daily counts of cardiovascular mortality were associated with PM2.5 and several of its species including EC, OC, nitrates, sulphates, potassium, copper and iron. For many of these species, there were significantly higher effect estimates among those with lower educational attainment and Hispanic individuals. For example, while essentially no association was observed for individuals who graduated from high school, an interquartile change in several of the components of PM2.5 was associated with a 3–5% increase in daily mortality among non-high school graduates.

Conclusion:

There is evidence that several PM2.5 constituents may represent important contributors to cardiovascular mortality. Many of these constituents are generated by motor vehicles, especially those with diesel engines, and by residential wood combustion. In addition, factors associated with low educational attainment may increase susceptibility to PM2.5 and its components.
Measurement of trends in incidence of work-related skin and respiratory diseases, UK 1996–2005
Authors: McNamee R , Carder M , Chen Y , Agius R
Published: April 2008

Objectives:

The ability to measure temporal trends in disease incidence is important, but valid methods are needed. This study investigates UK trends during 1996–2005 in work-related skin and respiratory diseases including non-malignant pleural disease, asthma, mesothelioma and pneumoconiosis and the potential for bias when using surveillance systems for this purpose.

Methods:

The volunteer reporters in three surveillance schemes were specialist physicians for skin diseases, specialist physicians for respiratory diseases and occupational physicians, respectively, who provided monthly reports of new cases of disease which they considered work related. Poisson regression models were used to investigate variation by calendar year (trend), season and reporter characteristics. Separately, temporal patterns in the probabilities of non-response and zero reports were investigated. Annual changes in disease incidences were compared between reporter groups.

Results:

There was little evidence of change in incidences of non-malignant pleural disease, mesothelioma, skin neoplasia and urticaria, but falls were seen for contact dermatitis and pneumoconiosis. Although the directions of change were similar across reporter groups, the magnitude of annual change in incidence was often inconsistent: for occupational asthma, it was −1.9% (95% CI −5.2 to 1.4) and −12.1% (95% CI−19.5 to −4.1) using respiratory and occupational physician reports, respectively. Response rates were high (∼85%), but non-response increased slightly with membership time, as did the probability of a zero return in some groups. Adjustment of results for presumed reporting fatigue led to an upward correction in some calendar trends.

Conclusions:

As some estimated changes in incidence based on volunteer reporting may be biased by reporting fatigue, apparent downward trends need to be interpreted cautiously. Differences in the population bases of the surveillance schemes and UK health service capacity constraints may also explain the differences in trends found here.
Temporal and spatial concordance in community composition of phytoplankton, zooplankton, macroinvertebrate, crayfish, and fish on the Precambrian Shield
Authors: Bowman Michelle F , Ingram Ron , Reid Ron A , Somers Keith M , Yan Norman D , Paterson Andrew M , Morgan George E , Gunn John M
Published: April 2008

Concordance among communities dictates how broadly we can extrapolate results derived from a set of ecosystems. We used Mantel tests to evaluate the degree of concordance in community composition among phytoplankton, zooplankton, benthic macroinvertebrate, crayfish, and fish in eight lakes near Dorset, Ontario, Canada. Spatial concordance across lakes at the decadal scale was stronger (mean Mantel r = 0.51, standard deviation (SD) = 0.20) than both intra-annual agreement (mean Mantel r = 0.38, SD = 0.20) and temporal concordance within a single lake (mean Mantel r = 0.20, SD = 0.15). The degree of temporal concordance was not related to climatic fluctuations, with the exception of increased spatial synchrony in phytoplankton communities in 1997. Strength of overall spatial concordance was most commonly related to variability in chemical attributes of the study lakes. An understanding of the determinants of concordance among taxon groups is germane to the advancement of ecology in general, as well as biodiversity conservation strategies, ecosystem monitoring, and impact diagnosis.
Statistical Analysis of Embedded Replicates in Mark–Recovery Experiments
Authors: Schnute Jon T.
Published: April 2008

This paper examines statistical theory related to a specialized mark–recovery experiment in which a group of fish is marked with coded wire tags (CWTs) cut sequentially from a wire roll. If the roll contains several codes embedded repetitively and if fish are selected randomly for marking, the resulting marked group automatically comprises several random subgroups called "embedded replicate" groups. When the fish are recovered, each subgroup can be identified by a distinct mark. Consequently, embedded replication appears to offer an easy technique for extending the information available from a conventional CWT experiment with only one code. The paper contends, however, that embedded replicate groups inherently provide no useful information beyond that obtained by treating them as a single group. In particular, the use of embedded replicates for variance estimation can be deceptive. Analytical results supporting these claims are presented for two cases of special interest. The paper also provides an overview of statistical methods that can be used, without recourse to embedded replication, to assess uncertainty in parameters commonly measured by mark–recovery experiments.
Deep Diving in Wild, Free-Ranging Beluga Whales, Delphinapterus leucas
Authors: Martin A. R. , Smith T. G.
Published: April 2008

Three adult female beluga whales, Delphinapterus leucas, were captured during summer in the Canadian high Arctic and equipped with satellite-linked radio transmitters that measured and recorded ambient pressure every 20 s. Diving behaviour was divisible into three distinct categories: (1) near-surface, (2) "spike" dives to 20–150 m depth, and (3) prolonged, flat-bottomed dives to a maximum depth of 350 m. The duration of these prolonged dives was 9.3–13.7 min, but the upper bound is known to be underestimated. Average descent rates varied between dives in the range 1.43–2.20 m/s and ascent rates between 1.23 and 1.84 m/s. Within periods of 20 s duration, maximum descent and ascent rates were 2.55 and 2.35 m/s, respectively. After most prolonged dives the rate of ascent declined progressively as the surface was approached, particularly in the final 100 m. Such dives were usually to, or near to, the seabed and were probably for foraging. Up to 42% of an animal's time could be spent at depths of 8 m or more.
Rent Capture in an Individual Transferable Quota Fishery
Authors: Grafton R. Quentin
Published: April 2008

The problem of capturing economic rent in a fishery regulated by an individual transferable quota scheme is addressed using a profit tax and a quota tax as two methods of rent collection. Using a theoretical model of a fishery with representative fishers employing different harvesting functions, the effects of the taxes are evaluated with respect to their ability to capture rent, flexibility to adjust to changes in the fishery, effects upon economic efficiency, the burden of taxation on different fishers, and ease of implementation. A quota tax is shown to be preferred over a comparable profit tax by those fishers who earn the highest average net returns on quota owned. A quota tax also has the potential to allow fishers to capture the full benefits of efficiency improvements. The profit tax can allow for greater risk sharing between the regulator and fishers and is able to capture the entire rent in the fishery in both the short and long run.
Generality of Microhabitat Suitability Models for Young Colorado River Cutthroat Trout (Oncorhynchus clarki pleuriticus) across Sites and among Years in Wyoming Streams
Authors: Bozek Michael A. , Rahel Frank J.
Published: April 2008

The generality of microhabitat-use and preference models for young-of-year (YOY) Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus) was tested across sites and years among geomorphically different streams. Depths, velocities, and substrate types used by YOY cutthroat trout often differed across both sites and years. These differences could only partially be explained as a result of differences in microhabitat availability. Microhabitat-use and preference models also varied in their ability to predict the amount of suitable microhabitat across sites. Estimates of suitable microhabitat abundance differed by up to 40% when microhabitat models were randomly used across sites. However, use of a composite model resulted in estimates of suitable microhabitat abundance that differed by less than 20% of that estimated by site-specific models. Therefore, composite models developed for a region may be a useful approach for assessing microhabitat when development of site-specific microhabitat models is not possible. We recommend that further assessment of model generality be conducted for other life stages and species prior to applying microhabitat models to sites other than those where the models were developed.
Identification and characterization of NBS–LRR class resistance gene analogs in faba bean (Vicia faba L.) and chickpea (Cicer arietinum L.)
Authors: Palomino C. , Satovic Z. , Cubero J.I. , Torres A.M.
Published: April 2008

A PCR approach with degenerate primers designed from conserved NBS–LRR (nucleotide binding site – leucine-rich repeat) regions of known disease-resistance (R) genes was used to amplify and clone homologous sequences from 5 faba bean (Vicia faba) lines and 2 chickpea (Cicer arietinum) accessions. Sixty-nine sequenced clones showed homologies to various R genes deposited in the GenBank database. The presence of internal kinase-2 and kinase-3a motifs in all the sequences isolated confirm that these clones correspond to NBS-containing genes. Using an amino-acid sequence identitiy of 70% as a threshold value, the clones were grouped into 10 classes of resistance-gene analogs (RGA01 to RGA10). The number of clones per class varied from 1 to 30. RGA classes 1, 6, 8, and 9 were comprised solely of clones isolated from faba bean, whereas classes 2, 3, 4, 5, and 7 included only chickpea clones. RGA10, showing a within-class identity of 99%, was the only class consisting of both faba bean and chickpea clones. A phylogenetic tree, based on the deduced amino-acid sequences of 12 representative clones from the 10 RGA classes and the NBS domains of 6 known R genes (I2 and Prf from tomato, RPP13 from Arabidopsis, Gro1–4 from potato, N from tobacco, L6 from flax), clearly indicated the separation between TIR (Toll/interleukin-1 receptor homology: Gro1–4, L6, N, RGA05 to RGA10)- and non-TIR (I2, Prf, RPP13, RGA01 to RGA04)-type NBS–LRR sequences. The development of suitable polymorphic markers based on cloned RGA sequences to be used in genetic mapping will facilitate the assessment of their potential linkage relationships with disease-resistance genes in faba bean and chickpea. This work is the first to report on faba bean RGAs.
UV photoelectron spectroscopic and computational study of 7-substituted cycloheptatrienes
Authors: Bajorek T , Werstiuk N H
Published: April 2008

The He(I) photoelectron (PE) spectra of cycloheptatriene (1), 7-methylcycloheptatriene (2), 7-methoxycycloheptatriene (3), 7-methylthiocycloheptatriene (4), and 7-diemthylaminocycloheptatriene (5) were recorded and interpreted using MO energies and ionization potentials acquired from B3PW91 calculations. Partial simulated PE spectra were in good agreement with the experimental results. The axial and equatorial conformers have distinct PE spectra as illustrated by simulation. The PE spectra of 2, 3, and 5 are representative of the equatorial conformers, while the PE spectrum of 4 was in accord with a 1:1 mixture of equatorial and axial conformational isomers based on spectral simulation. The calculated free energy differences between the equatorial and axial conformers are in the order of 2 kcal mol–1 (1 cal = 4.184 J) for compounds 2, 3, and 5, where the equatorial conformational isomer is lowest in energy. In the case of 4, the equatorial conformer was only marginally lower in energy than its axial counterpart, where the free energy difference is 0.1 kcal mol–1.Key words: 7-substituted cycloheptatrienes, He(I) photoelectron spectroscopy, B3PW91, spectral simulation.
Susceptibility of white spruce to attack by spruce beetles during the early years of an outbreak in Alaska
Authors: Hard John S. , Werner Richard A. , Holsten Edward H.
Published: April 2008

Twenty-five variable sample plots were examined in mature white spruce (Piceaglauca (Moench) Voss) stands, in southcentral Alaska. These stands, located in the Canyon Creek – Quartz Creek valley on the Kenai Peninsula, have been infested by spruce beetle, Dendroctonusrufipennis (Kirby), since 1978. Diameter was not an important criterion for spruce susceptibility to attack or death unless large diameter was coupled with slower than average radial growth in the last 5 years, an apparent indicator of current tree vigor. A sigmoid transformation of percent mortality of spruce was inversely related to the logarithm of mean cumulative radial growth of spruce in the last 5 years and was directly related to number of spruce per hectare greater than 24.1 cm in diameter. This relationship is portrayed graphically as a rudimentary stand hazard rating model.
Influence of canopy removal on oak forest floor decomposition
Authors: Yin Xiwei , Perry James A. , Dixon Robert K.
Published: April 2008

We compared leaf and forest floor mass loss rates over 2 years on undisturbed (NC), shelterwood-cut (SC0), and clear-cut (CC) sites in a Quercus forest at the Hardie's Creek Forest, Wisconsin, U.S.A. Litterbag techniques and a budgetary approach based on forest floor surveys and litterfall estimations were used. SC0 and NC variables did not differ until final harvest on SC0 (creating SC1). Over a 6-month period, 19% of initial cellulose (filter disk) mass was lost from litterbags placed on SC1 compared with 71% on NC. Leaf mass loss from litterbags was consistently slower on CC than on NC. Rates of mass loss to the upper (01) and lower (02) forest floor horizons in 1985 and total forest floor mass loss rate in both years did not differ among sites; mass loss rate for 01 was lower on CC than on NC, but higher for 02 in 1986. Differences in mass loss rates between CC and NC were attributed to changes in environment (ambient temperature and water content of the soil and forest floor) that were induced by clear-cutting. We suggest that the effects of canopy removal on mass loss from leaf litter appear to vary with regional climatic variables, while the effects on overall forest floor mass loss rate may be buffered by compensation among various forest floor horizons in most areas.
Height-growth and site-index curves for jack pine in north central Ontario
Authors: Carmean Willard H. , Lenthall Daniel J.
Published: April 2008

Height-growth patterns for jack pine (Pinusbanksiana Lamb.) were studied using stem analyses from dominant and codominant trees on 141 plots in north central Ontario. All plots were in natural, well-stocked, even-aged stands 50 years of age or older. Data from 32 of the 141 plots were randomly selected to confirm results, the remaining 109 plots were used for computing the curves. Height-growth curves were developed using a five-parameter Chapman–Richards nonlinear regression that expressed height as a function of age and site index. A site-index prediction equation was also computed using a similar model that expressed site index as a function of age and tree height. Estimated site index using height-growth curves based on the 109 computation plots agreed closely with site index observed from stem analyses on the 32 confirmation plots. Major results were as follows: (i) height-growth curves based on breast-height age were more accurate than curves based on total age; (ii) polymorphic height-growth patterns were related to site index, becoming more curvilinear as site index increased; (iii) average height-growth patterns were similar for jack pine growing on four glacial landforms: shallow and deep moraines, outwashed glacial sands, and lacustrine clays and silts; and (iv) height-growth patterns for ages less than 50 years were very similar to patterns of the commonly used Plonski curves for jack pine site classes in Ontario, but after 50 years, height growth was somewhat better for all sites than predicted by the Plonski curves.
Prediction of forest-floor moisture content on jack pine cutovers
Authors: Chrosciewicz Z.
Published: April 2008

Moisture contents of organic forest-floor materials were studied by strata on a clear-cut jack pine (Pinusbanksiana Lamb.) site in relation to slash distribution and changes in both duff moisture code and fine fuel moisture code, the two weather-based components of the Canadian Forest Fire Weather Index System. The best-fitting curvilinear regression (Y = a + b/X) of the duff moisture code showed distinctive patterns of variation, so that both the surface and subsurface forest-floor strata were consistently moister under slash cover than in slash openings, and for each of these two slash conditions, the subsurface forest-floor strata were consistently moister than the surface strata. Combinations of these materials down to mineral soil showed intermediate moisture contents both in slash openings and under slash cover. The straight line regression (Y = a + bX) of the fine fuel moisture code was the best-fitting moisture content relationship for the surface forest-floor materials, but only in slash openings; under slash cover, the curvilinear regression (Y = a + b/X) of the duff moisture code was more suitable. The coefficients of correlation, r, as derived from these varied regressions, were all very highly significant at P < 0.001.
Postthinning growth and yield of row-thinned and selectively thinned loblolly and slash pine plantations
Authors: Baldwin Jr. V. C. , Feduccia D. P. , Haywood J. D.
Published: April 2008

This study compared growth responses in planted loblolly pine (Pinustaeda L.) and slash pine (P. elliottii Engelm.) stands thinned by using three row-felling methods and at the same density levels, three selective felling methods. The study plots were in six plantations, aged 15–22 years, located in central Louisiana. Growth was measured 5 and 10 years after plot installation. Site index varied from 19.5 to 31.7 m (base age 50) and initial planting densities ranged from 1993 to 2989 trees/ha. Study results show there will likely be less diameter increment and less net basal area and cubic-metre volume per unit area growth and yield, and the growth will be in smaller-sized trees, if row thinning is used rather than selective thinning from below. These differences will probably be greater in slash pine plantations than in loblolly pine plantations.
SYNCHRONOUS QUANTUM GRAVITY
Authors: CIANFRANI FRANCESCO , MONTANI GIOVANNI
Published: April 2008

The implications of restricting the covariance principle within a Gaussian gauge are developed both on a classical and a quantum level. Hence, we investigate the cosmological issues of the obtained Schrödinger Quantum Gravity with respect to the asymptotically early dynamics of a generic Universe. A dualism between time and the reference frame fixing is then inferred.
CURVATURE-SPIN COUPLING FROM THE SEMI-CLASSICAL LIMIT OF THE DIRAC EQUATION
Authors: CIANFRANI FRANCESCO , MONTANI GIOVANNI
Published: April 2008

The notion of a classical particle is inferred from Dirac quantum fields on a curved space-time, by an eikonal approximation and a localization hypothesis for amplitudes. This procedure allows to define a semi-classical version of the spin-tensor from internal quantum degrees of freedom, which has a Papapetrou-like coupling with the curvature.
Effective Field Theory and Finite-Density Systems
Authors: Furnstahl Richard J. , Rupak Gautam , Schäfer Thomas
Published: April 2008

This review gives an overview of effective field theory (EFT) as applied at finite density, with a focus on nuclear many-body systems. Uniform systems with short-range interactions illustrate the ingredients and virtues of many-body EFT; we also survey the varied frontiers of EFT for finite nuclei and nuclear matter.
Family Structure and the Reproduction of Inequalities
Authors: McLanahan Sara , Percheski Christine
Published: April 2008

Over the past four decades, income inequality has increased and family structures have diversified. We argue that family structure has become an important mechanism for the reproduction of class, race, and gender inequalities. We review studies of income inequality and family structure changes and find a wide range of estimates of the correlation. We discuss how increases in income inequality may lead to increases in single motherhood, particularly among less educated women. Single motherhood in turn decreases intergenerational economic mobility by affecting children's material resources and the parenting they experience. Because of the unequal distribution of family structure by race and the negative effects of single motherhood, family structure changes exacerbate racial inequalities. Gender inequalities also increase as mothers incur more child-related costs and fewer fathers experience family life with children.
Volume-sensitive NADPH oxidase activity and taurine efflux in NIH3T3 mouse fibroblasts
Authors: Friis Martin Barfred , Vorum Katrine Gribel , Lambert Ian Henry
Published: April 2008

Reactive oxygen species (ROS) are produced in NIH3T3 fibroblasts during hypotonic stress, and H2O2 potentiates the concomitant release of the organic osmolyte taurine (Lambert IH. J Membr Biol 192: 19–32, 2003). The increase in ROS production [5-(and-6)-carboxy-2′, 7′-dichlorodihydrofluorescein diacetate fluorescence] is detectable after a reduction in the extracellular osmolarity from 335 mosM (isotonic) to 300 mosM and reaches a maximal value after a reduction to 260 mosM. The swelling-induced ROS production is reduced by the flavoprotein inhibitor diphenylene iodonium chloride (25 μM) but is unaffected by the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester, indicating that the volume-sensitive ROS production is NADPH oxidase dependent. NIH3T3 cells express the NADPH oxidase components: p22phox, a NOX4 isotype; p47phox; and p67phox (real-time PCR). Exposure to the Ca2+-mobilizing agonist ATP (10 μM) potentiates the release of taurine but has no effect on ROS production under hypotonic conditions. On the other hand, addition of the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA, 100 nM) or the lipid messenger lysophosphatidic acid (LPA, 10 nM) potentiates the swelling-induced taurine release as well as the ROS production. Overexpression of Rac1 or p47phox or p47phox knockdown [small interfering (si)RNA] had no effect on the swelling-induced ROS production or taurine release. NOX4 knockdown (siRNA) impairs the increase in the ROS production and the concomitant taurine release following osmotic exposure. It is suggested that a NOX4 isotype plus p22phox account for the swelling-induced increase in the ROS production in NIH3T3 cells and that the oxidase activity is potentiated by PKC and LPA but not by Ca2+.