bluuebunny/crossref_metadata_2025 huggingface dataset:
Progressive intercarrier and co‐channel interference mitigation for underwater acoustic multi‐input multi‐output orthogonal frequency‐division multiplexing
Authors: Huang Jianzhong , Zhou Shengli , Huang Jie , Preisig James , Freitag Lee , Willett Peter
Published: February 2012

Multi‐input multi‐output orthogonal frequency‐division multiplexing (MIMO‐OFDM) has been actively studied for high data rate communications over the bandwidth‐limited underwater acoustic (UWA) channels. Unlike existing receivers that treat the intercarrier interference (ICI) as additive noise, in this paper, the proposed receiver considers ICI explicitly together with the co‐channel interference (CCI) due to parallel transmissions in MIMO‐OFDM. Using a recently developed progressive receiver framework, the proposed receiver starts with low‐complexity ICI‐ignorant processing and then progresses to ICI‐aware processing with increasing ICI levels. The key components of the proposed receiver include the following: (1) compressed sensing‐based sparse channel estimation, (2) soft‐input soft‐output minimum mean square error/Markov chain Monte Carlo detector for interference mitigation, and (3) soft nonbinary low‐density parity check decoding. In addition to simulation, we use real data from the Surface Processes and Acoustic Communications Experiment 2008 (SPACE08) and the Mobile Acoustic Communications Experiment 2010 (MACE10) to verify the system performance, where the transmitter in SPACE08 was stationary and that in MACE10 was slowly moving. Simulation and experimental results show that explicitly addressing ICI and CCI significantly improves the performance of MIMO‐OFDM in UWA systems. Copyright © 2012 John Wiley & Sons, Ltd.
Dutch House Martins Delichon urbicum gain blood parasite infections over their lifetime, but do not seem to suffer
Authors: Piersma Theunis , van der Velde Marco
Published: February 2012

In a southern Spanish population of the colonial-breeding Afrotropical migrant House Martins Delichon urbicum, a high overall prevalence of (molecularly assayed) haemosporidian infections (in the non-parasitological literature usually denoted with the inclusive term ‘malaria’) was associated with negative fitness consequences for individuals carrying single or double infections. To verify this in a northern population, we here report on the occurrence of malaria in 112 fledgling and 358 adult House Martins from The Netherlands. Repeatability of molecular essays was 94.4% (n = 125). Malaria was not found in any of the fledglings, but 77% of the adults carried single or double infections of two Haemoproteus haplotypes (Delurb1, Delurb2) and five Plasmodium haplotypes (GRW2, GRW9, GRW11, COLL6 and Turdus1). The two Haemoproteus and two of the Plasmodium haplotypes overlapped with nine haplotypes observed in Spain, with Dutch birds showing another four. Haemoproteus infections were common (occurring in 70% of adult samples) and Plasmodium was rare (9%). Molecularly sexed females with blood parasite infections tended towards a higher chance of double infection (33%) than males (23%). Of 64 cases of birds captured in successive years, 23% showed no change in infection status, 5% lost infection, and there was an 85% chance for adults to gain a ‘malaria’ type. Within a single breeding season, infection status did not change in 6 of 13 cases (46%). However, in 6 of the 7 cases of change (86%), there was loss of a Haemoproteus infection. Infection status did not correlate with body mass or body size, tail asymmetry, occurrence of louse flies, nor with the likelihood of recapture in the subsequent year. The limited evidence so far suggests that House Martins get infected away from the European breeding grounds.
Applying Western decision-making theory to the study of transport infrastructure development in China: The case of the Harbin metro
Authors: Groenleer Martijn , Jiang Tingting , de Jong Martin , de Bruijn Hans
Published: February 2012

In recent decades, China has undergone massive urban transformation, an important component of which is transport infrastructure development. Although Western observers often hail China’s decision making on megaprojects as effective and efficient, this image deserves scrutiny. Political power and decision-making processes in China are not as centralized as many tend to believe, the field of policy actors can be diffuse and issues can be highly contested. Consequently, although some tremendous successes have been reported, not all large infrastructure projects have proceeded smoothly. This article unveils how decision-making processes on large infrastructure projects in China evolve, and why projects sometimes take much longer than might have been expected on the basis of the dominant image of Chinese decision making. It does so by presenting an in-depth study of a decision-making process that took much longer than initially foreseen: the design and construction of the Harbin metro system.
Amelanotic melanoma of the mandible: A case report
Authors: Kawasaki Goro , Yanamoto Souichi , Yoshitomi Izumi , Mizuno Akio , Fujita Shuichi , Umeda Masahiro
Published: February 2012

Amelanotic melanoma of the oral mucosa is extremely rare. We describe herein our experience of amelanotic melanoma arising in the mandibular mucosa. An 85‐year‐old woman was referred to our clinic with swelling of the left lower gingival mucosa. The histopathological diagnosis was amelanotic melanoma, as determined by immunohistochemical examination. The tumor cells were positive for S‐100, Melan‐A, HMB‐45, and vimentin. The patient declined surgical treatment, so she received irradiation therapy. At a total dose of 10 Gy, the patient exhibited lassitude, so we terminated radiotherapy. Bleeding from the tumor persisted, and the patient developed anemia and hypouresis. She also contracted pneumonia. The patient’s general condition worsened, and she died.
David Margrett: A Black Missionary in the Revolutionary Atlantic
Authors: LOCKLEY TIM
Published: February 2012

David Margrett was a black missionary sent by the Countess of Huntingdon to preach to slaves in South Carolina and Georgia in 1774. Margrett did not confine his preaching in America to spiritual matters, instead speaking out against the system of slavery itself, and offering himself as a “second Moses.” Margrett's message was not well received by authorities in South Carolina, indeed he was fortunate to escape with his life. This article argues that Margrett was a product both of his evangelical training, where speaking out on important matters was encouraged, and also of his British environment, where anti-slavery voices were becoming increasingly prominent. The story of David Margrett demonstrates how black Britons received and interpreted the message of Christianity, and in particular how they used their faith as a means to attack slavery.
Silencing of essential genes by RNA interference inHaemonchus contortus
Authors: ZAWADZKI J. L. , KOTZE A. C. , FRITZ J.-A. , JOHNSON N. M. , HEMSWORTH J. E. , HINES B. M. , BEHM C. A.
Published: February 2012

In this study we assessed three technologies for silencing gene expression by RNA interference (RNAi) in the sheep parasitic nematodeHaemonchus contortus. We chose as targets five genes that are essential inCaenorhabditis elegans(mitr-1, pat-12, vha-19, glf-1andnoah-1), orthologues of which are present and expressed inH. contortus, plus four genes previously tested by RNAi inH. contortus(ubiquitin, tubulin, paramyosin, tropomyosin). To introduce double-stranded RNA (dsRNA) into the nematodes we tested (1) feeding free-living stages ofH. contortuswithEscherichia colithat express dsRNA targetting the test genes; (2) electroporation of dsRNA intoH. contortuseggs or larvae; and (3) soaking adultH. contortusin dsRNA. For each gene tested we observed reduced levels of mRNA in the treated nematodes, except for some electroporation conditions. We did not observe any phenotypic changes in the worms in the electroporation or dsRNA soaking experiments. The feeding method, however, elicited observable changes in the development and viability of larvae for five of the eight genes tested, including the ‘essential’ genes,Hc-pat-12, Hc-vha-19andHc-glf-1. We recommend theE. colifeeding method for RNAi inH. contortusand provide recommendations for future research directions for RNAi in this species.
Once upon a time, there was a pulchritudinous princess . . .: The role of word definitions and multiple story contexts in children's learning of difficult vocabulary
Authors: WILKINSON KATHRYN S. , HOUSTON-PRICE CARMEL
Published: February 2012

The close relationship between children's vocabulary size and their later academic success has led researchers to explore how vocabulary development might be promoted during the early school years. We describe a study that explored the effectiveness of naturalistic classroom storytelling as an instrument for teaching new vocabulary to 6- to 9-year-old children. We examined whether learning was facilitated by encountering new words in single versus multiple story contexts, or by the provision of age-appropriate definitions of words as they were encountered. Results showed that encountering words in stories on three occasions led to significant gains in word knowledge in children of all ages and abilities, and that learning was further enhanced across the board when teachers elaborated on the new words’ meanings by providing dictionary definitions. Our findings clarify how classroom storytelling activities can be a highly effective means of promoting vocabulary development.
Solitary IgM phase II response has a limited predictive value in the diagnosis of acute Q fever
Authors: RAVEN C. F. H. , HAUTVAST J. L. A. , HERREMANS T. , LEENDERS A. C. A. P. , SCHNEEBERGER P. M.
Published: February 2012

We investigated the positive predictive value (PPV) of a solitary positive immunoglobulin M (IgM) phase II response for the serodiagnosis of acute Q fever detected with either an indirect immunofluorescence assay (IFA) or an enzyme-linked immunosorbent assay (ELISA). Initial and follow-up sera from patients suspected of acute Q fever were included if initially only IgM phase II tested positive with IFA in 2008 (n=92), or ELISA in 2009 (n=85). A seroconversion for Q fever was defined as an initial sample being IgG phase II negative but positive in the follow-up sample. The PPV of an initial isolated IgM phase II result detected by IFA or ELISA was 65% and 51%, respectively, and therefore appeared not to adequately predict acute Q fever. For this reason it cannot be used as a diagnostic criterion nor should it be included in public health notification without confirmation with other markers or a follow-up serum sample.
Feminist Security Studies: Celebrating an Emerging Field
Authors: Tickner J. Ann
Published: February 2012

As feminist international relations enters its third decade as a subdiscipline within IR, it is particularly fitting that we recognize and celebrate the stimulating and important new research that is being done in Feminist Security Studies. In the early days of feminist IR, feminists tended to stay away from security studies, at least as it is conventionally defined, a tendency that, fortunately, is no longer the case. The rich and varied research being done by contributors to this volume is evidence that the field has taken off and that its research agendas are flourishing.
Beyond Sex/Gender: The Feminist Body of Security
Authors: Wilcox Lauren
Published: February 2012

What makes Feminist Security Studies such an exciting field for me is the depth and diversity of feminists grappling with key issues of the politics of war, peace, and security who are also concerned with sovereignty and autonomy, the meaning and nature of violence, and the connections among violence, subjectivity, and embodiment. Feminists across the disciplines have done much to render problematic the equation of bodies and subjects for their own political purposes, a political/theoretical move that has enormous implications for the way in which we think about the practices of security. In thinking through and even beyond “gender,” feminists in security studies are poised to ask the question of how we might rethink not only how security practices are gendered, but also how the very nature of “security” has lent itself to particular conceptions of “the body” (Butler 2004).
Looking Forward, Conceptualizing Feminist Security Studies
Authors: Sjoberg Laura
Published: February 2012

In previous work, I characterized Feminist Security Studies as pluralistic, but transformative:

Research in Feminist Security Studies reformulates mainstream approaches to traditional security issues, foregrounds the roles of women and gender in conflict and conflict resolution, and reveals the blindness of security studies to issues that taking gender seriously shows as relevant to thinking about security. Together, these works, as a research program, show that gender analysis is necessary, conceptually, for understanding international security, important for analyzing causes and predicting outcomes, and essential to thinking about solutions and promoting positive change in the security realm. (Sjoberg 2009a, 184; see also Sjoberg 2006, 2009b; Sjoberg and Martin 2010.)
A positive carbon feedback to ENSO and volcanic aerosols in the tropical terrestrial biosphere
Authors: Gurney Kevin R. , Castillo Kendra , Li Bo , Zhang Xia
Published: February 2012

The relationship between the El Niño/Southern Oscillation (ENSO), volcanic aerosol, and the carbon cycle has been characterized through analyses of atmospheric CO2, biogeochemical modeling and recently through inverse estimation. However, the studies to date contain weaknesses that make quantitative assessment of the relationship unreliable. Here we present a systematic quantification of the relationship between ENSO, volcanic aerosols and regional net carbon exchange using results from the TransCom Atmospheric CO2Inversion Intercomparison and a simple 2‐step regression method. A modified ENSO index (ENSOτ) is created by estimating the component of ENSO variability that is linearly uncorrelated to aerosol optical depth, and the relationships are estimated by performing correlation analysis with the TransCom 3 tropical terrestrial carbon flux estimates. Flux anomalies from the tropical land regions (Tropical America, Northern Africa, Tropical Asia) show statistically significant correlations with anomalies of ENSOτ, with carbon exchange lagging the ENSOτ by two to six months. Further analysis by season and warm phase/cold phase shows the ENSOτ warm phase explaining >70% of the variability in tropical net carbon exchange. Tropical Asia shows the largest response with positive carbon flux anomalies following two to three months behind the peak of the ENSOτ warm phase. Total tropical land carbon flux anomalies of +0.59 GtC/year result from a typical (one standard deviation) warm ENSOτ event and are consistent with estimates of carbon loss via tropical fire.
Localized density enhancements in the magnetosheath: Three‐dimensional morphology and possible importance for impulsive penetration
Authors: Karlsson T. , Brenning N. , Nilsson H. , Trotignon J.‐G. , Vallières X. , Facsko G.
Published: February 2012

We use Cluster multipoint density measurements, using the spacecraft potential, to identify localized density enhancements (>50%) in the magnetosheath, and estimate their three‐dimensional morphology and orientation. Typically one dimension of the density enhancements is shorter than others, is directed perpendicular to the background magnetic field, and varies from ∼0.1 RE to 10 RE, with the other two dimensions a factor 3–10 greater. The density structures are oriented with the longest sides in the general direction of the bow shock and magnetopause. Examples of density structures both convecting with the same velocity as the background magnetosheath flow (“embedded plasmoids”), and convecting with an excess xGSE velocity component (“fast plasmoids”) are found. Possible importance for the impulsive penetration mechanism for plasma entry in the magnetosphere is analyzed by comparing the results to laboratory results, via a parameter scaling. The estimation of the three‐dimensional topology of the density enhancements will enable a comparison with localized magnetosheath populations inside the magnetosphere, observed earlier, to determine if these originate from penetrated magnetosheath density enhancements.
Pairwise scale space comparison of time series with application to climate research
Authors: Godtliebsen F. , Holmström L. , Miettinen A. , Erästö P. , Divine D. V. , Koc N.
Published: February 2012

In this paper, we study how sea surface temperature variations in the North Atlantic and the Norwegian Sea are correlated with the climate in the Northern Hemisphere in late Holocene. The analysis is performed by testing statistical hypotheses through novel scale space methodologies. In late Holocene, the proposed techniques reveal that the climate development in the subpolar North Atlantic has been incoherent with the development in the Norwegian Sea and the Northern Hemisphere. A prominent discrepancy between the three analyzed series is identified for the periods associated with the Medieval Warm Period and the Little Ice Age. A divergence between the oceanic series and the global Northern Hemisphere temperature estimate detected in the twentieth century is in line with the inferred imprint of recent climate change which suggests accentuated warming, in particular over continental regions. Overall, the results obtained by scale space analysis underscore the significance of the northern North Atlantic in shaping the climate globally, mainly through changes in the strength and structure of the Atlantic meridional overturning circulation.
Mean Atlantic meridional overturning circulation across 26.5°N from eddy‐resolving simulations compared to observations
Authors: Xu X. , Schmitz W. J. , Hurlburt H. E. , Hogan P. J.
Published: February 2012

Observations along 26.5°N are used to examine the time mean structure of the Atlantic meridional overturning circulation (AMOC) in eddy‐resolving simulations with the Hybrid Coordinate Ocean Model (HYCOM). The model results yield a 5 year mean AMOC transport of 18.2 Sv, compared to 18.4 Sv based on data. The modeled northward limb of the AMOC has a vertical structure similar to observations. The southward limb is shallower than observed but deeper than other ocean general circulation models and includes a secondary transport maximum near 4000 m corresponding to Nordic Seas Overflow Water. The modeled flow through the Florida Strait and the deep western boundary current (DWBC) east of Abaco, Bahamas, are also approximately consistent with observations. The model results are used to clarify the sources of the northward AMOC transport and to explore the circulation pattern of the southward transport in the western subtropical North Atlantic in the range 18–33°N. About 14.1 Sv of the modeled northward AMOC transport is through the Florida Strait and the remainder through the mid‐ocean, primarily in the Ekman layer, but also below 600 m. The modeled AMOC transport is about 2/3 surface water and 1/3 Antarctic Intermediate Water with no contribution from the thermocline water in between. In the western subtropical North Atlantic the model results depict a complicated deep circulation pattern, associated with the complex bathymetry. The DWBC flows southward then eastward in both the upper and lower North Atlantic Deep Water (NADW) layers but with different offshore recirculation pathways, and there exists a second, more northern branch of eastward flow in the lower NADW layer.
Fog‐ and cloud‐induced aerosol modification observed by the Aerosol Robotic Network (AERONET)
Authors: Eck T. F. , Holben B. N. , Reid J. S. , Giles D. M. , Rivas M. A. , Singh R. P. , Tripathi S. N. , Bruegge C. J. , Platnick S. , Arnold G. T. , Krotkov N. A. , Carn S. A. , Sinyuk A. , Dubovik O. , Arola A. , Schafer J. S. , Artaxo P. , Smirnov A. , Chen H. , Goloub P.
Published: February 2012

Large fine mode–dominated aerosols (submicron radius) in size distributions retrieved from the Aerosol Robotic Network (AERONET) have been observed after fog or low‐altitude cloud dissipation events. These column‐integrated size distributions have been obtained at several sites in many regions of the world, typically after evaporation of low‐altitude cloud such as stratocumulus or fog. Retrievals with cloud‐processed aerosol are sometimes bimodal in the accumulation mode with the larger‐size mode often ∼0.4–0.5μm radius (volume distribution); the smaller mode, typically ∼0.12 to ∼0.20 μm, may be interstitial aerosol that were not modified by incorporation in droplets and/or aerosol that are less hygroscopic in nature. Bimodal accumulation mode size distributions have often been observed from in situ measurements of aerosols that have interacted with clouds, and AERONET size distribution retrievals made after dissipation of cloud or fog are in good agreement with particle sizes measured by in situ techniques for cloud‐processed aerosols. Aerosols of this type and large size range (in lower concentrations) may also be formed by cloud processing in partly cloudy conditions and may contribute to the “shoulder” of larger‐size particles in the accumulation mode retrievals, especially in regions where sulfate and other soluble aerosol are a significant component of the total aerosol composition. Observed trends of increasing aerosol optical depth (AOD) as fine mode radius increased suggests higher AOD in the near‐cloud environment and higher overall AOD than typically obtained from remote sensing owing to bias toward sampling at low cloud fraction.
Effects of NOxcontrol and plume mixing on nighttime chemical processing of plumes from coal‐fired power plants
Authors: Brown Steven S. , Dubé William P. , Karamchandani Prakash , Yarwood Greg , Peischl Jeff , Ryerson Thomas B. , Neuman J. Andrew , Nowak John B. , Holloway John S. , Washenfelder Rebecca A. , Brock Charles A. , Frost Gregory J. , Trainer Michael , Parrish David D. , Fehsenfeld Frederick C. , Ravishankara A. R.
Published: February 2012

Coal‐fired electric power plants produce a large fraction of total U.S. NOx emissions, but NOx from this sector has been declining in the last decade owing to installation of control technology. Nighttime aircraft intercepts of plumes from two different Texas power plants (Oklaunion near Wichita Falls and W. A. Parish near Houston) with different control technologies demonstrate the effect of these reductions on nighttime NOxoxidation rates. The analysis shows that the spatial extent of nighttime‐emitted plumes to be quite limited and that mixing of highly concentrated plume NOx with ambient ozone is a determining factor for its nighttime oxidation. The plume from the uncontrolled plant had full titration of ozone through 74 km/2.4 h of downwind transport that suppressed nighttime oxidation of NO2 to higher oxides of nitrogen across the majority of the plume. The plume from the controlled plant did not have sufficient NOx to titrate background ozone, which led to rapid nighttime oxidation of NO2 during downwind transport. A plume model that includes horizontal mixing and nighttime chemistry reproduces the observed structures of the nitrogen species in the plumes from the two plants. The model shows that NOx controls not only reduce the emissions directly but also lead to an additional overnight NOx loss of 36–44% on average. The maximum reduction for 12 h of transport in darkness was 73%. The results imply that power plant NOxemissions controls may produce a larger than linear reduction in next‐day, downwind ozone production following nighttime transport.
Potentially active faults in the rapidly eroding landscape adjacent to the Alpine Fault, central Southern Alps, New Zealand
Authors: Cox Simon C. , Stirling Mark W. , Herman Frederic , Gerstenberger Matthew , Ristau John
Published: February 2012

Potentially active faults are exposed in the steep glaciated topography of the central Southern Alps, New Zealand, immediately adjacent to the Alpine Fault plate boundary. Four major faults exposed along the flanks of three of the highest mountain ranges strike 10–23 km (potentially 40 km) NNE oblique to the Alpine Fault, dipping 57° ± 12° NW in the opposite direction. Youngest discernable motions were reverse dip‐slip, accommodating both margin‐perpendicular shortening and dextral margin‐parallel components of plate motion. Kinematic analysis yields a compression axis (295/10° ± 9° trend or plunge) equivalent to the contemporary shortening determined from seismological and geodetic studies, suggesting the faults may be active, although definitive evidence for recent movement or single event displacements is lacking. There are 106 other potentially active faults mapped in central Southern Alps with strike lengths 4–73 km. Earthquake parameters were assigned from fault trace lengths and historical earthquake statistics, indicating potential for MW 5.5–7.4 earthquakes at recurrence intervals of 1000–10,000 years. Such long recurrence intervals are consistent with the faults having little surface expression, with rapid erosion of these seismically agitated mountains erasing any evidence of surface rupture during periods between earthquakes. The central Southern Alps faults exemplify the difficulty in fully deciphering long‐term (e.g., Holocene or Quaternary) records of seismicity in tectonically active regions with rapidly evolving landscapes. Although there may be little evidence of surface ruptures remaining in the landscape, the faults are still an important potential source of earthquakes and seismic hazard.
White House Budget Proposal Favorable Overall for Federal Science Agencies
Authors: Showstack Randy
Published: February 2012

President Barack Obama's proposed federal budget of $3.8 trillion for fiscal year (FY) 2013, released on 13 February, provides an overall favorable funding picture for federal science agencies in a tight economic environment. However, there are also a number of proposed decreases, including a sharp cut to NASA's Planetary Science account. Overall, the budget proposal includes $140.8 billion for the federal investment in research and development, a 1.4% increase above the FY 2012 enacted level. Funding for federal basic and applied research would be $64 billion, 3.3% above FY 2012 enacted levels. Funding for defense research and development (R&D) would decrease to $75.9 billion, a drop of 1.5%; nondefense R&D would increase 5% to $64.9 billion.
Congress Examines Nuclear Waste Disposal Recommendations
Authors: Showstack Randy
Published: February 2012

During an 8 February U.S. congressional hearing to examine how to move forward on dealing with spent nuclear fuel and to review other recommendations of the recently released final report of the White House‐appointed Blue Ribbon Commission on America's Nuclear Future (BRC), Yucca Mountain was the 65,000‐ton gorilla in the room. BRC's charge was to conduct a comprehensive review of policies to manage the back end of the nuclear fuel cycle and recommend a new strategy for dealing with the 65,000 tons of spent nuclear fuel currently stored at 75 sites around the country and the 2000 tons of new spent fuel being produced each year. However, BRC specifically did not evaluate Yucca Mountain. A 26 January letter from BRC to U.S. secretary of energy Steven Chu states, “You directed that the Commission was not to serve as a siting body. Accordingly, we have not evaluated Yucca Mountain or any other location as a potential site for the storage of spent nuclear fuel or disposal of high‐level waste nor have we taken a position on the administration's request to withdraw the Yucca Mountain license application.”
Jing and King Receive Mineral and Rock Physics Graduate Research Awards
Authors: Anonymous
Published: February 2012

Zhicheng Jing and Daniel King have been awarded the 2011 Mineral and Rock Physics Graduate Research Award, given annually to one or more promising young scientists for outstanding contributions achieved during their Ph.D. research. Recipients of this award are engaged in experimental and/or theoretical studies of Earth and planetary materials with the purpose of unraveling the physics and chemistry that govern their origin and physical properties. Jing's thesis is entitled “Equation of state of silicate liquids.” King's thesis is entitled “Stress‐driven melt segregation and reactive melt infiltration in partially molten rocks deformed in torsion with applications to melt extraction from Earth's mantle.” They both were formally presented with the award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif.
Reconciling conflicting accounts of plasmaspheric hiss
Authors: Schultz Colin
Published: February 2012

Arcing from pole to pole, the Van Allen radiation belts are formed from a large number of protons or electrons trapped high above the Earth, the high‐energy particles locked in paths dictated by the terrestrial magnetic field. Separating the outer electron Van Allen belt from the inner belt is the so‐called slot region, a safe zone with reduced radiation levels. Not a necessary feature of the radiation belts, the safe zone is formed when low‐frequency radio waves known as plasmaspheric hiss kick the high‐energy electrons out of their trapped orbits. Understanding the safe zone depends on sorting out the hiss waves' basic properties, including their spatial and frequency distributions, and their typical direction of propagation—not an easy task, as indicated by decades of conflicting observations.
Record Arctic ozone depletion could occur again
Authors: Balcerak Ernie
Published: February 2012

In the winter of 2010–2011, ozone levels above the Arctic declined to record lows, creating the first Arctic ozone hole, similar to the well‐known Antarctic ozone hole. Scientists believe the ozone depletion was due partly to unusually cold temperatures in the stratosphere above the Arctic, as colder stratospheric temperatures make ozone‐destroying chemicals such as chlorine more active. As global climate change continues, the Arctic stratosphere is expected to get colder, but levels of ozone‐destroying chemicals should decline, as emissions of these chemicals were banned by the Montreal Protocol. To try to learn more about Arctic ozone dynamics and determine whether the Arctic ozone hole is likely to recur, Sinnhuber et al. looked at satellite observations of temperature, ozone, water vapor, and chemicals that affect ozone in the Arctic atmosphere. They also used a model to determine how sensitive ozone levels are to stratospheric temperatures and chemistry. They found that their model accurately reproduced measured conditions. Their model suggests that stratospheric temperatures 1°C lower than in the 2010–2011 winter would result in locally nearly complete ozone depletion in the Arctic lower stratosphere with current levels of chemicals. A 10% reduction in ozone‐depleting chemicals would be offset by a 1°C decrease in stratospheric temperatures.
Moored instruments show decadal drop in AMOC strength
Authors: Schultz Colin
Published: February 2012

The Atlantic branch of the global thermohaline circulation, known as the Atlantic meridional overturning circulation (AMOC), carries warm surface waters to the north and cold water southward along the seafloor, redistributing energy throughout the ocean basin. Changes in AMOC behavior have been pegged as an important source of interannual variability for the climates of countries ringing the North Atlantic Ocean. Recent modeling results, along with geologic evidence, have some researchers concerned that the system may ultimately collapse. Though interannual and decadal variabilities in the flow rate of the AMOC are consistent features in numerical simulations, direct observations of the circulation's changing behavior have generally eluded detection.
Pairing simple and complex models could improve predictions
Authors: Balcerak Ernie
Published: February 2012

Environmental management often relies on complex numerical models. Such models can represent complex natural processes in detail but generally take a lot of computational time to run and even greater computational effort to calibrate. Associating uncertainties with predictions made by these models can also be difficult. Conversely, simple models run faster and are easier to calibrate, but they often leave out key physical details or make simplifying assumptions that could introduce inaccuracy and inhibit uncertainty characterization. To overcome the shortcomings of both types of models, Doherty and Christensen developed a method that uses paired simple and complex models to improve predictive accuracy and quantify predictive uncertainty. The approach could be applied to problems in hydrology, ecology, and many other areas of environmental or climate science. (Water Resources Research, doi:10.1029/2011WR010763, 2011)
Internal tides measured with multisatellite altimetry
Authors: Balcerak Ernie
Published: February 2012

Ocean tides flowing over rough topography generate internal tides, which may transport the tidal energy more than 2000 kilometers away from the generation sites. Eventual breaking of these waves produces turbulence and influences the mixing of heat and chemicals, ocean circulation, and global climate. However, mapping internal tides from their generation to dissipation over such great distances poses a significant challenge. Satellite altimeters, with nearly global coverage, can capture the approximately 2‐centimeter sea surface height deflection caused by an internal tide (corresponding to tens of meters of subsurface displacements).
Flows in polar cap ionosphere could trigger auroral substorms
Authors: Balcerak Ernie
Published: February 2012

Auroral substorms, in which aurorae dramatically brighten and become highly dynamic, occur often and seem to be triggered by electric currents in the ionosphere at high latitude. However, scientists do not know the details of how auroral substorms begin and what drives their expansion and controls their duration. Plasma flows within the ionosphere's polar cap region had not generally been considered to be a driver of auroral substorms, but some recent studies have suggested that mesoscale plasma flows from the polar cap could cross the polar cap boundary and contribute to triggering of flows that may bring new plasma earthward and lead to the onset of substorms.
Central California's warm waves a clue to changing coastal currents
Authors: Schultz Colin
Published: February 2012

A quarter of the way up the crest of the California coast, a giant L‐shaped headland reaches out to a peak at Point Conception. To the north of the headland, winds blowing off the Pacific Ocean induce strong coastal upwelling, bringing cold ocean water to the surface. To the east of Point Conception, warm water traveling up the California coast gets trapped in the Santa Barbara Channel, its path blocked by upwelling to the west and Santa Cruz, Santa Rosa, and San Miguel islands to the south. Previous research showed that when a low‐pressure system passes through the region, the upwelling‐inducing winds can die down, freeing the warm water trapped in the Santa Barbara Channel to continue its poleward journey. Using satellite, high‐frequency radar, and instrumented moorings to observe water temperature and current velocity, Washburn et al. determined the intricacies of these poleward propagating warm‐water flows.
Traveling supraglacial lakes observed on Antarctic ice shelf
Authors: Balcerak Ernie
Published: February 2012

A sequence of lakes on top of the George VI ice shelf in Antarctica has been observed to move along the boundary of the ice shelf with Alexander Island. LaBarbera and MacAyeal analyzed satellite images of the George VI ice shelf in Antarctica taken from 2001 through 2010. They found that the supraglacial lakes move in a direction and with a speed that differs from ice shelf flow: parallel to the grounding line of the ice shelf, in the manner of a traveling wave. The authors present a simple model to show how the lakes form in the depressions associated with compressions of the ice sheet. The study could help researchers better understand the dynamics of the ice shelf. (Geophysical Research Letters, doi:10.1029/2011GL049970, 2011)
Identification of the topology and functional domains of PAQR10
Authors: Jin Ting , Xu Daqian , Ding Qiurong , Zhang Yixuan , Mao Chenqian , Pan Yi , Wang Zhenzhen , Chen Yan
Published: February 2012

PAQR10 (progestin and adipoQ receptor 10) is a Golgi-localized protein that is able to enhance the retention and activation of Ras proteins in the Golgi apparatus, subsequently leading to a sustained ERK (extracellular-signal-regulated kinase) signalling. However, little is known about the topology and functional domains of PAQR10. In the present study, we extensively dissected and analysed the structure of PAQR10. The topology analysis reveals that PAQR10 is an integral membrane protein with its N-terminus facing the cytosol. Multiple domains, including the membrane-proximal region at the N-terminus, the membrane-proximal region at the C-terminus and the three loops facing the cytosol, were found to be required for PAQR10 to reside in the Golgi apparatus, to stimulate ERK phosphorylation and to tether Ras to the Golgi apparatus. Furthermore, when PAQR10 was artificially forced to be expressed in the endoplasmic reticulum, it could neither mobilize Ras to the Golgi apparatus nor increase ERK phosphorylation. Finally, the PAQR10 mutants that lost Golgi localization failed to promote differentiation of PC12 cells. Collectively, the results of the present study indicate that Golgi localization is indispensable for PAQR10 to implement its regulatory functions in the Ras signalling cascade.
Conformational transitions of proteins engaged in DNA double-strand break repair, analysed by tryptophan fluorescence emission and FRET
Authors: Stankova Katia , Ivanova Katia , Mladenov Emil , Rosidi Bustanur , Sharma Aparna , Boteva Rayna , Iliakis George
Published: February 2012

We analysed protein–DNA and protein–protein interactions relevant to the repair of DNA DSBs (double-strand breaks) by NHEJ (non-homologous end-joining). Conformational transitions in mammalian DNA ligases III (LigIII) and IV (LigIV), as well as in PARP-1 [poly(ADP-ribose) polymerase-1], were analysed upon binding to double-stranded DNA by changes in tryptophan emission and FRET (Förster resonance energy transfer) from tryptophan to DNA-conjugated Alexa Fluor® 532. For LigIII, two non-equivalent high- and low-affinity DNA-binding sites are detected interacting sequentially with DNA. PARP-1 displays a single high-affinity DNA-binding site and can displace bound DNA fragments from the low-affinity site of LigIII, consistent with its mediator role in LigIII–DNA interactions. For the LX [LigIV–XRCC4 (X-ray cross-complementation group 4)] complex, a single DNA-binding site is detected. Binding of Ku to DNA was accompanied by conformational changes in the protein and intermolecular FRET from dansyl chromophores of the labelled Ku to the Alexa Fluor® chromophores of Alexa Fluor® 532-conjugated DNA. The average distance of 5.7 nm calculated from FRET data is consistent with a location of Ku at the very end of the DNA molecule. Binding of LX to Ku–DNA complexes is associated with conformational changes in Ku, translocating the protein further towards the DNA ends. The protein–protein and protein–DNA interactions detected and analysed generate a framework for the characterization of molecular interactions fundamental to the function of NHEJ pathways in higher eukaryotes.
Effects of ghrelin on homocysteine‐induced dysfunction and inflammatory response in rat cardiac microvascular endothelial cells
Authors: Wang Dongjuan , Wang Haichang , Luo Peng , Hwang Andrew , Sun Dongdong , Wang Yabin , Zhang Zheng , Liu Nan , Wang Shenxu , Li Chengxiang , Cao Feng
Published: February 2012

Ghrelin is a well‐characterized hormone that has protective effects on endothelial cells. Elevated HCY (homocysteine) can be a cardiovascular risk factor, but it is not known whether ghrelin can inhibit HCY‐induced dysfunction and inflammatory response in rat CMECs (cardiac microvascular endothelial cells). We found that HCY treatment for 24 h inhibited proliferation and NO (nitric oxide) secretion, but with increased cell apoptosis and secretion of cytokines in CMECs. In contrast, ghrelin pretreatment significantly improved proliferation and NO secretion, and inhibited cell apoptosis and secretion of cytokines in HCY‐induced CMECs. In addition, Western blot assay showed that NF‐κB (nuclear factor κB) and cleaved‐caspase 3 expression were elevated, and PCNA (proliferating cell nuclear antigen) and eNOS (endothelial nitric oxide synthase) expression were decreased after treatment with HCY, which was significantly reversed by pretreatment with ghrelin. The data suggest that ghrelin inhibits HCY‐induced CMEC dysfunction and inflammatory response, probably mediated by inhibition of NF‐κB activation.
New approach to isolate mesenchymal stem cell (MSC) from human umbilical cord blood
Authors: Hussain Issam , Magd Salah A. , Eremin Oleg , El‐Sheemy Mohamed
Published: February 2012

HUCB (human umbilical cord blood) has been frequently used in clinical allogeneic HSC (haemopoietic stem cell) transplant. However, HUCB is poorly recognized as a rich source of MSC (mesenchymal stem cell). The aim of this study has been to establish a new method for isolating large number of MSC from HUCB to recognize it as a good source of MSC. HUCB samples were collected from women following their elective caesarean section. The new method (Clot Spot method) was carried out by explanting HUCB samples in mesencult complete medium and maintained in 37°C, in a 5% CO2 and air incubator. MSC presence was established by quantitative and qualitative immunophenotyping of cells and using FITC attached to MSC phenotypic markers (CD29, CD73, CD44 and CD105). Haematopoietic antibodies (CD34 and CD45) were used as negative control. MSC differentiation was examined in neurogenic and adipogenic media. Immunocytochemistry was carried out for the embryonic markers: SOX2 (sex determining region Y‐box 2), OLIG‐4 (oligodendrocyte‐4) and FABP‐4 (fatty acid binding protein‐4). The new method was compared with the conventional Rosset Sep method. MSC cultures using the Clot Spot method showed 3‐fold increase in proliferation rate compared with conventional method. Also, the cells showed high expression of MSC markers CD29, CD73, CD44 and CD105, but lacked the expression of specific HSC markers (CD34 and CD45). The isolated MSC showed some differentiation by expressing the neurogenic (SOX2 and Olig4) and adipogenic (FABP‐4) markers respectively. In conclusion, HUCB is a good source of MSC using this new technique.
Features of Thiolated Ligands Promoting Resistance to Ligand Exchange in Self-Assembled Monolayers on Gold Nanoparticles
Authors: Chen Xinyue , Qoutah Wafaa W. , Free Paul , Hobley Jonathan , Fernig David G. , Paramelle David
Published: February 2012

An important feature necessary for biological stability of gold nanoparticles is resistance to ligand exchange. Here, we design and synthesize self-assembled monolayers of mixtures of small ligands on gold nanoparticles promoting high resistance to ligand exchange. We use as ligands short thiolated peptidols, e.g. H-CVVVT-ol, and ethylene glycol terminated alkane thiols (HS-C11-EG4). We present a straightforward method to evaluate the relative stability of each ligand shell against ligand exchange with small thiolated molecules. The results show that a ligand with a ‘thin’ stem, such as HS-C11-EG4, is an important feature to build a highly packed self-assembled monolayer and provide high resistance to ligand exchange. The greatest resistance to ligand exchange was found for the mixed ligand shells of the pentapeptidols H-CAVLT-ol or H-CAVYT-ol and the ligand HS-C11-EG4 at 30:70 (mole/mole). Mixtures of ligands of very different diameters, such as the peptidol H-CFFFY-ol and the ligand HS-C11-EG4, provide only a slightly lower stability against ligand exchange. These ligand shells are thus likely to be suitable for long-term use in biological environments. The method developed here provides a rapid screening tool to identify nanoparticles likely to be suitable for use in biological and biomedical applications.
Synthesis and Application of New Photocrosslinkers for Poly(ethylene glycol)
Authors: Mehenni Hakim , Pourcelle Vincent , Gohy Jean-François , Marchand-Brynaert Jacqueline
Published: February 2012

Photocrosslinking of polyethylene glycol (PEG) using exogenous agents is a convenient way to produce branched PEG from commercial sources thus avoiding the tricky synthesis of new reactive and functional polymers. In this study, we synthesized two series of new photocrosslinkers, i.e. bis-fluorophenyl azide and bis-trifluoromethyl diazirine, which under soft UV-irradiation produce reactive species (i.e. nitrene and carbene respectively) that insert into the C–H bond of the polymer backbone, building new bridges between macromolecular chains. These photocrosslinkers are different in terms of behaviour under irradiation and affinity for the target substrate (i.e. PEG). Thus, practical conditions for photocrosslinking of a 10-kDa PEG were studied and followed by NMR and size-exclusion chromatography. In particular, we investigated irradiation in bulk or in solvent, at different irradiation times, with several concentrations of PEG and photolinkers. Finally, we were able to design a procedure to obtain soluble crosslinked PEGs of 300 kDa.