bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of clustering and nonstationarity in the time distribution of large worldwide earthquakes
Authors: Lombardi Anna Maria , Marzocchi Warner
Published: February 2007

The purpose of this paper is to characterize the statistical distribution of worldwide largest earthquakes. We analyze the distribution of worldwide shallow events withMs7.0+ since 1900, by following the Occam's razor philosophy; we start from the simplest possible model (stationary Poisson process), and we inspect more complicated models only if the data show significant departures from the simplest one. The results show two important characteristics; first, worldwideMs7.0+ earthquakes tend to cluster in time and space, with features similar to smaller events. Second, for some seismic regions there is evidence in favor of long‐term fluctuations of the earthquake rate. These results support the hypothesis of universality, suggesting that an ETAS model with a background varying with time can be considered reliable to describe the seismicity distribution over a wide space‐time‐magnitude window. From a practical point of view, our findings suggest that the paradigm that seismic zones are stationary systems, implicitly assumed in seismic hazard assessment, should be regarded with caution.
Trace gas and particulate emissions from the 2003 southern California wildfires
Authors: Mühle J. , Lueker T. J. , Su Y. , Miller B. R. , Prather K. A. , Weiss R. F.
Published: February 2007

In October 2003, thirteen major wildfires in southern California burned more than 300,000 hectares of mainly chaparral biome. High‐precision in situ trace gas and particle measurements of the wildfire plumes in La Jolla, California, showed a high degree of correlation among carbon dioxide (CO2), methane (CH4), nonmethane hydrocarbons, and methyl halide mixing ratios, as well as with particle number concentrations (10–300 nm and 500–2500 nm aerodynamic diameter). Aerosol time‐of‐flight mass spectrometry of individual aerosol particles (50–2500 nm range) showed that 70–85% had typical biomass burning signatures (levoglucosan coupled with potassium). Only 5–18% of particles in the 50–300 nm range had vehicle signatures. Molar trace gas enhancement ratios (ERs) versus ethane and CO2were calculated and showed a narrow age distribution, consistent with the short distance from the wildfires. ERs for N2O and CH3CCl3versus CO2were determined, but correlations were poor. No significant CH2Cl2or CHCl3emissions were detected. CO2emissions from the nearby Cedar fire were estimated both with a simple Lagrangian atmospheric transport model and a burned area approach and extrapolated to 11 Tg CO2for the total burned area in southern California. Total CO2, CH4, C2‐hydrocarbons, benzene, toluene, methyl chloride, methyl iodide, and PM2.5emissions were ∼0.2–3.5% of yearly global extratropical forest fire emissions and more than 28% of CH4, C6H6, and PM2.52003 San Diego and South Coast Air Basins anthropogenic emissions. Particle distributions and single particle chemistry are discussed. PM2.5considerably exceeded the EPA short‐term exposure limit.
Nanoclimate environment of cyanobacterial communities in China's hot and cold hyperarid deserts
Authors: Warren‐Rhodes Kimberley A. , Rhodes Kevin L. , Liu Shuangjiang , Zhou Peijin , McKay Christopher P.
Published: February 2007

This paper analyzes linkages between lithic (lithobiontic, lithophytic) cyanobacterial community (LCC) abundance and climate across a wide range of environmental conditions and geographical distance in China's northwest region, an area containing some of the world's oldest, driest and most isolated deserts. In situ monitoring and long‐term climate data show that extreme heterogeneity in liquid water availability characterizes the LCC environment across multiple spatial and temporal scales, with rainfall and snowmelt being the main moisture sources. Mean annual precipitation (MAP) primarily dictates LCC ecology across sites, but the interacting effects of temperature, moisture and light create a gradient of soil liquid water (ALW, 505–1839 hr yr−1) and conditions suitable for metabolic activity (200–922 hr yr−1) that also correlate with LCC abundance (0.99 ± 0.2% to 12.6 ± 1.8%). In situ soil temperatures indicate a minimum range of thermal tolerance for LCC in China's deserts of −23.8°C to 53.8°C. Through a comparison of similar available climate data for other deserts, we conclude that from a microbial physiological standpoint, although the hyperarid core of the Atacama Desert represents the driest nanoclimate environment recorded and the Dry Valleys in Antarctica represent the coldest desert conditions, it is the high‐altitude deserts in the Qinghai‐Tibetan Plateau that offer the coldest and driest recorded extremes for LCC on Earth.
Charge carrier transport in metal phthalocyanine based disordered thin films
Authors: Mahapatro Ajit Kumar , Ghosh Subhasis
Published: February 2007

The charge carrier transport in metal phthalocyanine based disordered thin films has been investigated. Charge carrier mobility in these disordered thin films strongly depends on the electric field and temperature due to hopping conduction. The applicability of two different Gaussian disorder models has been compared and evaluated for charge carrier transport using simple experimental results and based on our extensive analysis, it has been found that spatial and energetic correlation is important in explaining the electrical transport in these organic semiconductors.
MeV heavy ion induced recrystallization of buried silicon nitride layer: Role of energy loss processes
Authors: Som T. , Sinha O. P. , Ghatak J. , Satpati B. , Kanjilal D.
Published: February 2007

We report on MeV heavy ion beam induced epitaxial crystallization of a buried silicon nitride layer. Transmission electron micrographs and selected area diffraction patterns are used to study the recrystallization of an ion beam synthesized layer. We observe complete recrystallization of the silicon nitride layer having good quality interfaces with the top and substrate Si. Recrystallization is achieved at significantly lower temperatures of 100, 150, and 200°C for oxygen, silicon, and silver ions, respectively. The fact that recrystallization is achieved at the lowest temperature for the oxygen ions is discussed on the basis of the energy loss processes.
Effect of nitrogen on the magnetic moment of α-Fe and FeCo alloys from first-principle calculations
Authors: Chandran Mahesh , Iorio Luana E. , Subramanian P. R.
Published: February 2007

The effect of nitrogen on the magnetization of α-Fe and Fe1−xCox alloys was studied within the spin-polarized density functional theory. For α-Fe, the average magnetic moment (per atom) μ increases with increasing concentration of interstitial nitrogen. The increase in moment occurs due to inter-atomic charge transfer, which increases the moment on the Fe atoms that are next-nearest neighbor to the N atom. In Fe1−xCox alloys, nitrogen suppresses the peak in μ(x) and shifts it to lower Co concentrations compared to the pure Fe-Co system. The decrease in moment in the FeCo-N system occurs due to competing inter-atomic (promoted by N) and intra-atomic (promoted by Co) charge transfer on the Fe atoms surrounding the N atom. The addition of nitrogen was not found to significantly increase the magnetization of α-Fe and Fe1−xCox alloys.
Effect of 3d, 4d, and 5d transition metal doping on damping in permalloy thin films
Authors: Rantschler J. O. , McMichael R. D. , Castillo A. , Shapiro A. J. , Egelhoff W. F. , Maranville B. B. , Pulugurtha D. , Chen A. P. , Connors L. M.
Published: February 2007

The effect of doping on the magnetic damping parameter of Ni80Fe20 is measured for 21 transition metal dopants: Ti, V, Cr, Mn, Co, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au. For most of the dopants, the damping parameter increases linearly with dopant concentration. The strongest effects are observed for the 5d transition metal dopants, with a maximum of 7.7×10−3 per atomic percent osmium.
Ultrasonic technique for extracting nanofibers from nature materials
Authors: Zhao Hong-Ping , Feng Xi-Qiao , Gao Huajian
Published: February 2007

This letter reports a simple and versatile approach for extracting bionanofibers from natural materials using the ultrasonic technique. Bionanofibers have been fabricated from various materials, e.g., spider and silkworm silks, chitin fibers, collagen, cotton, bamboo, and ramee and hemp fibers. The obtained nanofibers have uniform diameters in the range of 25–120nm and possess the optimized hierarchical structures and superior properties of natural materials which have formed after the evolution of many millions of years. This methodology might be valuable to provide a convenient, versatile, and environmentally benign fabrication method for producing bionanofibers at an industrial scale.
Fermi-level pinning at polycrystalline silicon-HfO2 interface as a source of drain and gate current 1∕f noise
Authors: Magnone P. , Crupi F. , Pantisano L. , Pace C.
Published: February 2007

The impact of a submonolayer of HfO2 sandwiched between the SiON gate dielectric and the polycrystalline silicon layer on the low frequency noise of a n-channel metal oxide semiconductor field effect transistor is investigated. Fermi-level pinning at polycrystalline silicon-HfO2 interface acts as a dramatic source of the drain noise due to charge carrier number fluctuations, and of the gate noise due to work function fluctuations. These 1∕f noise measurements are a strong indicator that the defects at the top HfO2/polycrystalline silicon interface, rather than bulk defects in the high-k layer, are responsible for the noise degradation observed in HfO2 gate dielectrics.
Exciton spin splitting in ultrathin InAs layers
Authors: Sun Zheng , Xu Z. Y. , Ji Yang , Sun B. Q. , Wang B. R. , Huang S. S. , Ni H. Q.
Published: February 2007

Unique spin splitting behaviors in ultrathin InAs layers, which show very different spin splitting characteristics between the InAs monolayer (ML) and submonolayer (SML) have been observed. While distinct spin splitting is observed in an InAs ML, no visible spin splitting is found in a 1∕3 ML InAs SML. In addition, the spin relaxation time in the 1∕3 ML InAs is found to be much longer than that in the 1 ML sample. These results are in good agreement with the theoretical prediction that the interexcitonic exchange interaction plays a dominant role in energy splitting, while the intraexciton exchange interaction controls the spin relaxation.
Highly enhanced flux pinning in Pb and rare earth codoped Bi-2212
Authors: Biju A. , Vinod K. , Sarun P. M. , Syamaprasad U.
Published: February 2007

The effect of codoping of Pb and rare earths [rare earths (REs)=La, Gd, and Yb] in Bi-2212 superconductor on structural, transport, and flux pinning properties was investigated in comparison with solo doping of REs. While the solo doping led to marked improvements in critical temperature (TC), critical current density (JC), and in-field JC (JC-B), the codoping exhibited very large enhancements in JC and JC-B at a relatively high temperature of 64K. Pb doping at Bi site improved the coupling between the two dimensional pancake vortices and the strongly coupled vortices were effectively pinned by the defects created at Sr∕Ca sites by RE doping.
Domestic Rate Reform in Northern Ireland: A Critical Review of Policy Options
Authors: McCluskey William J , Lim Lay Cheng , Davis Peadar T
Published: February 2007

Local government finance, and in particular the basis of domestic rating, is currently the subject of a major review in Northern Ireland. The authors have conducted empirical research into a comparison between the present rating system and two alternative options—a banded system or a property-specific discrete-value system. Derry City Council is used as a case study to gauge the likely redistributive effects of changes to the system. The findings are seen as significant in describing the effects of each policy regime at a local level in terms of winners and losers. In addition, the impact of the policy options in relation to a measure of income deprivation was investigated. The results indicate that a discrete-value system performs best in terms of minimising the effect of rate redistribution and providing for a more fair and equitable local tax.
Corporations and the Governance of Environmental Risk
Authors: Gouldson Andrew , Bebbington Jan
Published: February 2007

The authors sketch a framework within which the contributions to this theme issue can be understood. In particular, they discuss various frames of reference or ways of thinking that can be brought to bear on the challenges that arise in evaluating attempts to govern environmental risks. The discussion is divided into three sections. First, they discuss the factors that have led to the emergence of new ways of governing those corporate activities that are associated with the generation or management of environmental risks. Second, they problematise these new forms of governance, adopting the United Nation's Global Compact as an example, and drawing particularly on the insights derived from the contrasting perspectives associated with communicative and strategic action. As an alternative to both of these perspectives, they next focus on the Foucauldian concept of governmentality. The need for analyses to consider (a) the nature of the ways in which different risks are problematised, (b) the character of different governance regimes, (c) the significance of the organising ideals that guide the operation, and (d) the evolution of the multidimensional processes through which risks are governed, are highlighted. They conclude by suggesting that new ‘governmental technologies’ are unlikely to enable either ‘governance at a distance’, for instance, by creating opportunities for new forms of engagement and new spaces of accountability, or ‘governance of the self’, for example, by instilling values and developing technologies which allow corporations to govern their own activities more effectively.
The Governance of Corporations, Technological Change, and Risk: Examining Industrial Perspectives on the Development of Genetically Modified Crops
Authors: Tait Joyce , Chataway Joanna
Published: February 2007

Why do corporations develop technologies which can be associated with the generation of various environmental risks and how are the technologies that they develop governed by factors within and around firms? The authors examine the factors that have motivated and guided technological innovation, based on an examination of multinational companies developing genetically modified (GM) crops for the European market. The analysis is based on an inherently interdisciplinary approach to the study of innovation, which incorporates factors that are governed endogenously through the processes within companies (that is, strategic decisionmaking) and exogenously through interactions between firms and their external constituents (that is, government policies and regulations, and stakeholder and public perspectives and engagements). It is found that the introduction of GM technologies in Europe has been shaped significantly by public perception and societal reactions. It is also found that the aspects of industry strategies which contributed most to the course of European public opposition to GM crops were: (a) the choice of first-generation GM products; (b) interactions between pesticide-product and biotechnology-product strategies in different companies, and industry's efforts to present their sector and its products as contributing to sustainable development; (c) cultural and world-view differences between companies; and (d) company responses to European biotechnology policies and risk regulation. It is demonstrated that actions which seem rational to individual actors (corporations, governments, public interest groups) can have counterintuitive, and often counterproductive, outcomes in the longer term and when considered from the perspective of interactions within broader governance processes.
The Battle for Hearts and Minds? Evolutions in Corporate Approaches to Environmental Risk Communication
Authors: Gouldson Andrew , Lidskog Rolf , Wester-Herber e
Published: February 2007

In recent years there has been a great deal of discussion on the potential for a shift away from modernistic or technocratic approaches to decisionmaking on risk towards more open, inclusive, and deliberative approaches. The authors consider (a) the reasons why some companies have taken the first step in this transition by exploring the potential of more open and communicative approaches to environmental risk management, and (b) the effects that opening up can have, particularly on perceived levels of trust between corporations and stakeholders on matters relating to environmental risk. For the companies surveyed, the nature of their activities, the significance of formative events, and the failure of more traditional forms of risk communication to reduce conflict and to build trust amongst stakeholders have impelled them to experiment with new approaches to risk communication. It is found that, in the short term, such experiments are seen by managers to have had mixed effects: in contexts where trust had already been lost, open engagement can lead to an initial deterioration in relations between companies and stakeholders. However, it is also argued that in the longer term trust can be built through such open engagements. It is suggested, therefore, that opening up and engaging on matters relating to environmental risk may lead to a ‘j-curve effect’, with an initial deterioration in levels of trust being followed by a gradual improvement in levels of credibility and shared understanding over time.
Production and decomposition dynamics of hydrogen peroxide in freshwater
Authors: Richard Luc E. , Peake Barrie M. , Rusak Steven A. , Cooper William J. , Burritt David J.
Published: February 2007

Environmental context. Hydrogen peroxide (H2O2) is the most stable reactive oxygen species (ROS) formed through irradiation of chromophoric dissolved organic matter (CDOM) in freshwater. It can act as a reductant or as an oxidant and decays largely through interaction with microorganisms via unknown mechanisms. In this way it can affect biological and chemical processes in natural waters and thus shape the ecosystem biogeochemistry.
Abstract. Hydrogen peroxide (H2O2) is widely recognised as the most stable of the reactive oxygen species produced by solar radiation-driven photochemical reactions in natural waters. H2O2 concentrations were determined in a shallow fresh water system (water of Leith, Dunedin, New Zealand) by flow-injection analysis (FIA) using an acridinium ester chemiluminescent reaction system. Daytime measurements of H2O2 concentration showed a rapid increase from early morning (15 nM) to 1300 hours (491 nM), consistent with photochemical formation, lagging maximum solar irradiance by ~1.5 h. The wavelength dependency of H2O2 formation was studied and it was shown that UV-B, UV-A and PAR contributed 40, 33 and 27%, respectively. The average formation rate was 339 nM h–1 during springtime. The influence of biotic communities on the rate of H2O2 decomposition was also studied and the majority of decomposition was due to particles smaller than 0.22 μm. The overall first order decay rate constant was of the order of 7.1 h–1. The bacterial and algal communities in the water column and on the riverbed were primarily responsible for the decomposition of H2O2.
Cation influence on sulfate leaching in allophanic soils
Authors: Cichota R. , Vogeler I. , Bolan N. S. , Clothier B. E.
Published: February 2007

We have examined the influence of the ionic composition of the soil solution on the movement of sulfate and calcium in 2 New Zealand soils with differing allophane content. For this study, we have carried out a series of miscible displacement experiments using repacked and intact soil columns, in which sulfate was applied in the presence of either calcium or potassium as the accompanying cation. Our results showed that sulfate leaching was significantly retarded in the soil with higher allophane content when applied with calcium. On the other hand, no effects were observed for all studied soils when potassium was used as the accompanying cation. In addition, in soils with high allophane content, calcium also had its retention increased when sulfate was present. The increase in sulfate adsorption was accompanied by corresponding increase in calcium adsorption. These findings evidenced the presence of co-adsorption, or ion-pair adsorption (IPA), in allophane-containing soils. The extent of this adsorption is dependent on the soil pH, the accompanying cation, and the allophane content of the soil.
Decomposition of sugarcane harvest residue in different climatic zones
Authors: Robertson Fiona A. , Thorburn Peter J.
Published: February 2007

Sugarcane in Australia is increasingly grown under the green cane trash blanket system where harvest residues (trash) are retained on the soil surface instead of being burnt. This is considered a more sustainable system, but relatively little is known about its effects on soil carbon (C) and nitrogen (N). As part of a study to understand the effects of trash retention on soil C and N dynamics, we measured the composition and decomposition of sugarcane trash in terms of dry matter (DM), C, and N in 5 field experiments in contrasting climatic conditions in Queensland and New South Wales.
The trash from newly harvested sugarcane contained large quantities of DM (7–12 t/ha) and C (3–5 t/ha), which could be estimated from cane yield, and significant quantities of N (28–54 kg/ha), which could not be predicted from cane yield. Trash quality was low (C : N  ratio >70) and it took a year for most of the trash to decompose. Cumulative thermal time was the variable most closely associated with cumulative DM and C decomposition. Variation in the rate of trash DM and C decomposition between sampling dates was partially related to temperature and rainfall at 2 of the 3 sites, but was considered to be influenced by other factors (such as soil, trash, and management) as much as by climate. There were 2 phases of decomposition: an early phase when C : N ratios were high and variable and net N loss or gain was not related to C loss; and a late phase when C : N ratios were much lower and similar across experiments and net N loss was related to C loss. The rate of N loss from trash during the first 12 months was slow (1–5 kg/month), which would have been of little immediate significance for plant growth. The potential value of trash for soil N supply lies in cumulative effects over the medium–long term.
Management of sugarcane harvest residues: consequences for soil carbon and nitrogen
Authors: Robertson Fiona A. , Thorburn Peter J.
Published: February 2007

The Australian sugar industry is moving away from the practice of burning the crop before harvest to a system of green cane trash blanketing (GCTB). Since the residues that would have been lost in the fire are returned to the soil, nutrients and organic matter may be accumulating under trash blanketing. There is a need to know if this is the case, to better manage fertiliser inputs and maintain soil fertility. The objective of this work was to determine whether conversion from a burning to a GCTB trash management system is likely to affect soil fertility in terms of C and N. Indicators of short- and long-term soil C and N cycling were measured in 5 field experiments in contrasting climatic conditions.
The effects of GCTB varied among experiments. Experiments that had been running for 1–2 years (Harwood) showed no significant trash management effects. In experiments that had been running for 3–6 years (Mackay and Tully), soil organic C and total N were up to 21% greater under trash blanketing than under burning, to 0.10 or 0.25 m depth (most of this effect being in the top 50 mm). Soil microbial activity (CO2 production) and soil microbial biomass also increased under GCTB, presumably as a consequence of the improved C availability. Most of the trash C was respired by the microbial biomass and lost from the system as CO2. The stimulation of microbial activity in these relatively short-term GCTB systems was not accompanied by increased net mineralisation of soil N, probably because of the greatly increased net immobilisation of N. It was calculated that, with standard fertiliser applications, the entire trash blanket could be decomposed without compromising the supply of N to the crop. Calculations of possible long-term effects of converting from a burnt to a GCTB production system suggested that, at the sites studied, soil organic C could increase by 8–15%, total soil N could increase by 9–24%, and inorganic soil N could increase by 37 kg/ha.year, and that it would take 20–30 years for the soils to approach this new equilibrium. The results suggest that fertiliser N application should not be reduced in the first 6 years after adoption of GCTB, but small reductions may be possible in the longer term (>15 years).
Effect of soil cultivation and winter pugging on fluorine distribution in soil profiles under pasture following long-term applications of phosphate fertilisers
Authors: Loganathan P. , Bretherton M. R. , Hedley M. J.
Published: February 2007

In situations where large amounts of soil are ingested, elevated fluorine (F) concentrations in topsoil under pasture may pose a potential F risk to grazing livestock. A study conducted on a Pallic Soil (Aeric Fragiaqualf in US Soil Taxonomy) under pasture in New Zealand showed that 21 years of annual applications of phosphate fertilisers (mostly single superphosphate; mean P rate of 27 kg/ha.year; 1985–2005) significantly increased total soil F concentrations down to 150 mm soil depth but had no effect at 180–210 mm depth. The topsoil (0–30 mm depth) F concentration increased from 140 to approximately 210 mg F/kg. For agricultural soils, these topsoil F concentrations are low and are unlikely to present any risk of chronic F toxicity to livestock at present, but continuous inputs of large amounts of F through P fertiliser applications will increase topsoil F concentrations to levels that may cause F toxicity in the future if accompanied by large amounts of soil ingestion. Cultivation of soil to 150 mm depth using a mouldboard plough once every 6–9 years during pasture renovation significantly increased total soil F concentration at 60–150 mm depth but had no effect on the surface and deeper soil horizons (0–60 and 150–210 mm depths). However, the amount of post-1985 fertiliser-derived F in the 0–60 mm depth as a percentage of the total amount of post-1985 fertiliser-derived F recovered in all depths within 210 mm was less for cultivated soil (31%) than for uncultivated soil (51%), indicating that cultivation can reduce the topsoil F concentration and hence the F risk to grazing animals. Moderate winter pugging of soil caused by dairy cattle had no effect on F distribution in soil profiles. The F distribution in the surface soil horizons (0–30 and 30–60 mm depths) predicted by an empirical computer-based F model corresponded reasonably well with the measured F values.
Rational redesign of the folding pathway of a modular protein
Authors: Lowe Alan R. , Itzhaki Laura S.
Published: February 2007

The modular structures of repeat proteins afford them distinct properties compared with globular proteins, enabling them to function in a large and diverse range of cellular processes. Here, we show that they can also have different folding mechanisms. Myotrophin comprises four ankyrin repeats stacked linearly to form an elongated structure. Using site-directed mutagenesis, we find that folding of wild-type myotrophin is initiated at the C-terminal repeats. However, close examination of the mutant chevron plots reveals that simple models are insufficient to describe all of the data, and double mutant analysis subsequently confirms that there are parallel folding pathways. Destabilizing mutations in the C-terminal repeats reduce flux through the wild-type pathway, making a new route accessible in which folding is initiated at the N-terminal repeats. Thus, the folding mechanism of the repeat protein is poised on a fulcrum: When one end of the molecule is perturbed, the balance shifts between the different nucleation sites. The vast majority of studies on small globular proteins indicate a single, well defined route between the denatured and native states. By contrast, the potential to initiate folding at more than one site may be a general feature of repeat proteins arising from the symmetry inherent in their structures. We show that this simple architecture makes it straightforward to direct the folding pathway of a repeat protein by design.
Herpes simplex virus type 1 mediates fusion through a hemifusion intermediate by sequential activity of glycoproteins D, H, L, and B
Authors: Subramanian Ravi P. , Geraghty Robert J.
Published: February 2007

Virus-induced membrane fusion can be subdivided into three phases defined by studies of class I and class II fusion proteins. During Phase I, two membranes are brought into close apposition. Phase II marks the mixing of the outer membrane leaflets leading to formation of a hemifusion intermediate. A fusion pore stably forms and expands in Phase III, thereby completing the fusion process. Herpes simplex virus type 1 (HSV-1) requires four glycoproteins to complete membrane fusion, but none has been defined as class I or II. Therefore, we investigated whether HSV-1-induced membrane fusion occurred following the same general phases as those described for class I and II proteins. In this study we demonstrate that glycoprotein D (gD) and the glycoprotein H and glycoprotein L complex (gHL) mediated lipid mixing indicative of hemifusion. However, content mixing and full fusion required glycoprotein B (gB) to be present along with gD and gHL. Our results indicate that, like class I and II fusion proteins, fusion mediated by HSV-1 glycoproteins occurred through a hemifusion intermediate. In addition, both gB and gHL are probably directly involved in the fusion process. From this, we propose a sequential model for fusion via HSV-1 glycoproteins whereby gD is required for Phase I, gHL is required for Phase II, and gB is required for Phase III. We further propose that glycoprotein H and gB are likely to function sequentially to promote membrane fusion in other herpesviruses such as Epstein–Barr virus and human herpesvirus 8.
Adenovirus-mediated gene delivery into mouse spermatogonial stem cells
Authors: Takehashi Masanori , Kanatsu-Shinohara Mito , Inoue Kimiko , Ogonuki Narumi , Miki Hiromi , Toyokuni Shinya , Ogura Atsuo , Shinohara Takashi
Published: February 2007

Spermatogonial stem cells represent a self-renewing population of spermatogonia, and continuous division of these cells supports spermatogenesis throughout the life of adult male animals. Previous attempts to introduce adenovirus vectors into spermatogenic cells, including spermatogonial stem cells, have failed to yield evidence of infection, suggesting that male germ cells may be resistant to adenovirus infection. In this study we show the feasibility of transducing spermatogonial stem cells by adenovirus vectors. When testis cells from ROSA26 Cre reporter mice were incubatedin vitrowith a Cre-expressing adenovirus vector, Cre-mediated recombination occurred at an efficiency of 49–76%, and the infected spermatogonial stem cells could reinitiate spermatogenesis after transplantation into seminiferous tubules of infertile recipient testes. No evidence of germ-line integration of adenovirus vector could be found in offspring from infected stem cells that underwent Cre-mediated recombination, which suggests that the adenovirus vector infected the cells but did not stably integrate into the germ line. Nevertheless, these results suggest that adenovirus may inadvertently integrate into the patient's germ line and indicate that there is no barrier to adenovirus infection in spermatogonial stem cells.
The EGF repeat and discoidin domain protein, SED1/MFG-E8, is required for mammary gland branching morphogenesis
Authors: Ensslin Michael A. , Shur Barry D.
Published: February 2007

SED1, also known as MFG-E8, is a secreted protein composed of two EGF repeats (the second of which contains an RGD motif) and two discoidin/Factor V/VIII C domains. SED1 is expressed by a wide range of cell types, where it participates in diverse cellular interactions, such as sperm binding to the egg coat and macrophage recognition of apoptotic lymphocytes. Although SED1 was originally identified as a milk protein, its function in the mammary gland remains unclear; suggested functions include inhibition of viral infection and clearance of apoptotic cells during mammary gland involution. We report here that SED1 has an unexpected obligatory role during mammary gland development. Unlike that seen in WT glands, SED1-null glands show severely reduced branching from epithelial ducts and from terminal end buds, which are thin and poorly developed. SED1 is expressed by both luminal and myoepithelial cells in the developing epithelial duct, and binds to α
v
integrin receptors on myoepithelial cells leading to MAPK activation and cell proliferation. The absence of SED1 leads to greatly reduced levels of activated MAPK and a concomitant reduction in cell proliferation and branching throughout the epithelial tree. These results suggest that SED1 contributes, at least partly, to the intercellular signaling between luminal and myoepithelial cells that is required for branching morphogenesis.
Evidence for a functional RNA element in the hepatitis C virus core gene
Authors: McMullan Laura K. , Grakoui Arash , Evans Matthew J. , Mihalik Kathleen , Puig Montserrat , Branch Andrea D. , Feinstone Stephen M. , Rice Charles M.
Published: February 2007

In the core protein-coding region of hepatitis C virus (HCV), evidence exists for both phylogenetically conserved RNA structures and a +1 alternative reading frame (ARF). To investigate its role in HCV infection, we introduced four stop codons into the ARF of a genotype 1a H77 molecular clone. The changes did not alter the core protein sequence, but were predicted to disrupt RNA secondary structures. An attenuated infection was established after inoculation of the mutant HCV RNA into an HCV naïve chimpanzee. The acute infection was atypical with low peak viremia, minimal alanine aminotransferase elevation, and early virus control by a diverse adaptive immune response. Sequencing circulating virus revealed progressive reversions at the third and then fourth stop codon. In cell culture, RNA replication of a genome with four stop codons was severely impaired. In contrast, the revertant genome exhibited only a 5-fold reduction in replication. Genomes harboring only the first two stop codons replicated to WT levels. Similarly, reversions at stop codons 3 and 4, which improved replication, were selected with recombinant, infectious HCV in cell culture. We conclude that ARF-encoded proteins initiating at the polyprotein AUG are not essential for HCV replication in cell culture or
in vivo
. Rather, our results provide evidence for a functionally important RNA element in the ARF region.
Mice cloned from skin cells
Authors: Li Jinsong , Greco Valentina , Guasch Géraldine , Fuchs Elaine , Mombaerts Peter
Published: February 2007

Adult stem cells represent unique populations of undifferentiated cells with self-renewal capacity. In many tissues, stem cells divide less often than their progeny. It has been widely speculated, but largely untested, that their undifferentiated and quiescent state may make stem cells more efficient as donors for cloning by nuclear transfer (NT). Here, we report the use of nuclei from hair follicle stem cells and other skin keratinocytes as NT donors. When keratinocyte stem cells (KSCs) were used as NT donors, 19 liveborn mice were obtained, 9 of which survived to adulthood. Embryonic keratinocytes and cumulus cells also gave rise to cloned mice. Although cloning efficiencies were similar (<6% per transferred blastocyst), success rates were consistently higher for males than for females. Adult keratinocyte stem cells were better NT donors than so-called transit amplifying (TA) keratinocytes in both sexes (1.6% vs. 0% in females and 5.4% vs. 2.8% in males). Our findings reveal skin as a source of readily accessible stem cells, the nuclei of which can be reprogrammed to the pluripotent state by exposure to the cytoplasm of unfertilized oocytes.
Drying a tuberculosis vaccine without freezing
Authors: Wong Yun-Ling , Sampson Samantha , Germishuizen Willem Andreas , Goonesekera Sunali , Caponetti Giovanni , Sadoff Jerry , Bloom Barry R. , Edwards David
Published: February 2007

With the increasing incidence of tuberculosis and drug resistant disease in developing countries due to HIV/AIDS, there is a need for vaccines that are more effective than the present bacillus Calmette–Guérin (BCG) vaccine. We demonstrate that BCG vaccine can be dried without traditional freezing and maintained with remarkable refrigerated and room-temperature stability for months through spray drying. Studies with a model
Mycobacterium
(
Mycobacterium smegmatis
) revealed that by removing salts and cryoprotectant (e.g., glycerol) from bacterial suspensions, the significant osmotic pressures that are normally produced on bacterial membranes through droplet drying can be reduced sufficiently to minimize loss of viability on drying by up to 2 orders of magnitude. By placing the bacteria in a matrix of leucine, high-yield, free-flowing, “vial-fillable” powders of bacteria (including
M. smegmatis
and
M. bovis
BCG) can be produced. These powders show relatively minor losses of activity after maintenance at 4°C and 25°C up to and beyond 4 months. Comparisons with lyophilized material prepared both with the same formulation and with a commercial formulation reveal that the spray-dried BCG has better overall viability on drying.
The Fas pathway is involved in pancreatic β cell secretory function
Authors: Schumann Desiree M. , Maedler Kathrin , Franklin Isobel , Konrad Daniel , Størling Joachim , Böni-Schnetzler Marianne , Gjinovci Asllan , Kurrer Michael O. , Gauthier Benoit R. , Bosco Domenico , Andres Axel , Berney Thierry , Greter Melanie , Becher Burkhard , Chervonsky Alexander V. , Halban Philippe A. , Mandrup-Poulsen Thomas , Wollheim Claes B. , Donath Marc Y.
Published: February 2007

Pancreatic β cell mass and function increase in conditions of enhanced insulin demand such as obesity. Failure to adapt leads to diabetes. The molecular mechanisms controlling this adaptive process are unclear. Fas is a death receptor involved in β cell apoptosis or proliferation, depending on the activity of the caspase-8 inhibitor FLIP. Here we show that the Fas pathway also regulates β cell secretory function. We observed impaired glucose tolerance in Fas-deficient mice due to a delayed and decreased insulin secretory pattern. Expression of PDX-1, a β cell-specific transcription factor regulating insulin gene expression and mitochondrial metabolism, was decreased in Fas-deficient β cells. As a consequence, insulin and ATP production were severely reduced and only partly compensated for by increased β cell mass. Up-regulation of FLIP enhanced NF-κB activity via NF-κB-inducing kinase and RelB. This led to increased PDX-1 and insulin production independent of changes in cell turnover. The results support a previously undescribed role for the Fas pathway in regulating insulin production and release.
A natively unfolded yeast prion monomer adopts an ensemble of collapsed and rapidly fluctuating structures
Authors: Mukhopadhyay Samrat , Krishnan Rajaraman , Lemke Edward A. , Lindquist Susan , Deniz Ashok A.
Published: February 2007

The yeast prion protein Sup35 is a translation termination factor, whose activity is modulated by sequestration into a self-perpetuating amyloid. The prion-determining domain, NM, consists of two distinct regions: an amyloidogenic N terminus domain (N) and a charged solubilizing middle region (M). To gain insight into prion conversion, we used single-molecule fluorescence resonance energy transfer (SM-FRET) and fluorescence correlation spectroscopy to investigate the structure and dynamics of monomeric NM. Low protein concentrations in these experiments prevented the formation of obligate on-pathway oligomers, allowing us to study early folding intermediates in isolation from higher-order species. SM-FRET experiments on a dual-labeled amyloid core variant (N21C/S121C, retaining wild-type prion behavior) indicated that the N region of NM adopts a collapsed form similar to “burst-phase” intermediates formed during the folding of many globular proteins, even though it lacks a typical hydrophobic core. The mean distance between residues 21 and 121 was ≈43 Å. This increased with denaturant in a noncooperative fashion to ≈63 Å, suggesting a multitude of interconverting species rather than a small number of discrete monomeric conformers. Fluorescence correlation spectroscopy analysis of singly labeled NM revealed fast conformational fluctuations on the 20- to 300-ns time scale. Quenching from proximal and distal tyrosines resulted in distinct fast and slower fluctuations. Our results indicate that native monomeric NM is composed of an ensemble of structures, having a collapsed and rapidly fluctuating N region juxtaposed with a more extended M region. The stability of such ensembles is likely to play a key role in prion conversion.
LITERATURE AND ART
Authors: Smith Paul
Published: February 2007

This special issue of
French Studies
examines a body of narratives featuring French art and artists published at representative periods during the nineteenth century (in both French and English). There are strong thematic continuities between many of the examples discussed, particularly as regards their concern over the social and economic position of the artist, and the nature and gendering of creativity. The
topoi
of the genius and the
raté
also recur throughout. Several texts are vehicles for voicing aesthetic and political positions. And many draw closely on contemporary figures, events, and debates for their content. Yet this special issue does not aim to identify a discursive unity so much as to exhibit the variety and richness of the art novel's evolution. It is also concerned to address some of the methodological issues involved in reading this kind of text, including the selectivity of the canon, intertextual connections, and the relationship between fiction and fact. It is hoped it will not only plot some new and unfamiliar material in an area still represented for most by a mere handful of ‘major’ texts, but also bring some of the questions involved by this expanded configuration of the field into sharper focus.
Cytogenetic characterization of six species of flatfishes with comments to karyotype differentiation patterns in Pleuronectiformes (Teleostei)
Authors: Azevedo M. F. C. , Oliveira C. , Pardo B. G. , Martínez P. , Foresti F.
Published: February 2007

The karyotypes and cytogenetic characteristics of flatfishes species Paralichthys orbignyanus, Paralichthys patagonicus, Citarichthys spilopterus and Etropus crossotus (Paralichthyidae), Bothus ocellatus (Bothidae) and Symphurus tessellatus (Cynoglossidae) were investigated by conventional [Giemsa staining, C‐banding, Ag‐ and chromomycin (CMA3)‐stainings] and molecular [in situ hybridization (ISH)] cytogenetic techniques. The results showed 2n = 46 and FN = 48 (2msm + 46sta) in P. orbignyanus, 2n = 46 and FN = 46 (46sta) in P. patagonicus, 2n = 26 and FN = 44 (18msm + 8sta) in C. spilopterus, 2n = 38 and FN = 64 (26msm + 12sta) in E. crossotus, 2n = 32 and FN = 50 (18msm + 14sta) in B. ocellatus, and 2n = 46 and FN = 62 (46msm + 62sta) in S. tessellatus. All species exhibited weak C‐band positive segments in terminal and centromeric positions of some chromosome pairs. Silver staining of the nucleolus organizer regions (Ag‐NOR) technique showed a single Ag‐NOR‐bearing chromosome pair in all species except E. crossotus. All these sites were CMA3 positive and showed clear ISH signals after probing with a 18S rRNA probe. Etropus crossotus presented until seven chromosomes with Ag‐NORs and CMA3 positively stained segments in five chromosome pairs. Conversely only one chromosome pair was identified with the ISH experiments in this species. The available results show that the fishes of the order Pleuronectiformes experienced a marked chromosome evolution that included reduction in diploid number, mainly due to Robertsonian rearrangements, and several chromosome inversions.
The timing and extent of ‘juvenile ovary’ phase are highly variable during zebrafish testis differentiation
Authors: Wang X. G. , Bartfai R. , Sleptsova‐Freidrich I. , Orban L.
Published: February 2007

Gonad differentiation in male zebrafish involves a transformation from a ‘juvenile ovary’ to testis. In our study, this phenomenon was analysed using a stable transgenic line (vas::egfp) created by Krovel & Olsen (Mechanisms of Development, 116: 141–150, 2002). Our data obtained by histological and immunohistochemical methods show that the onset of enhanced green fluorescent protein (EGFP) expression marks the conversion of the bipotential gonad into a ‘juvenile ovary’, and its subsequent decrease in the males indicates transformation into a testis. Furthermore, during the ‘juvenile ovary’ stage, a high level of variation was observed among individuals not only in the starting point and duration of EGFP expression but also in its intensity. The intensity of reporter expression in the males ranged from a high level of expression – similar to that observed in females – to invisible expression and correlated with the number of oocytes, the shape of ‘juvenile ovary’ and its lumen. Therefore, the authors conclude that although all males develop ‘juvenile ovaries’, they differ vastly in the extent of their commitment toward femaleness during this stage before testis differentiation. The differentiating zebrafish testis shows morphological features similar to those of the transforming gonad of protogynous hermaphrodites, and therefore, it could be a good model for the study of the process of female‐to‐male sex change in adult teleosts.
Allelic and haplotypic diversity at the major histocompatibility class II within domesticated Australian Atlantic salmon (Salmo salar L.)
Authors: Wynne J. W. , Cook M. T. , Holmes B. H. , Elliott N. G.
Published: February 2007

Variation within the major histocompatibility (MH) class II alpha gene (Sasa‐DAA) was compared between domesticated Australian Atlantic salmon and their ancestral Canadian population. The level of Sasa‐DAA and MH class II beta gene (Sasa‐DAB) sequence variation was also examined within the Australian population and compared with that published for European Atlantic salmon populations. In contrast to variation previously reported for non‐coding microsatellite loci, a high level of MH class II allelic variation has been maintained within the domesticated Australian populations. Furthermore, a high level of Sasa‐DAA and Sasa‐DAB allele sequence diversity was also observed and exceeded that reported for other cultured Atlantic salmon populations. The number of Sasa‐DAB allele sequences (14) surpassed the number of Sasa‐DAA allele sequences (9) to produce 14 unique class II haplotypes. We conclude that the Australian Atlantic salmon populations show high MH class II allelic and haplotypic variation compared with both its ancestral Canadian population and other cultured Atlantic salmon populations.