bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric organic matter in clouds: exact masses and molecular formula identification using ultrahigh-resolution FT-ICR mass spectrometry
Authors: Zhao Y. , Hallar A. G. , Mazzoleni L. R.
Published: December 2013

Abstract. Clouds alter the composition of atmospheric aerosol by acting as a medium for interactions between gas- and particulate-phase substances. To determine the cloud water atmospheric organic matter (AOM) composition and study the cloud processing of aerosols, two samples of supercooled clouds were collected at the Storm Peak Laboratory near Steamboat Springs, Colorado (3220 m a.s.l.). Approximately 3000 molecular formulas were assigned to ultrahigh-resolution mass spectra of the samples after using a reversed-phase extraction procedure to isolate the AOM components from the cloud water. Nitrogen-containing compounds (CHNO compounds), sulfur-containing compounds (CHOS and CHNOS compounds) and other oxygen-containing compounds (CHO compounds) with molecular weights up to 700 Da were observed. Average oxygen-to-carbon ratios of ∼0.6 indicate a slightly more oxidized composition than most water-soluble organic carbon identified in aerosol studies, which may result from aqueous oxidation in the clouds. The AOM composition indicates significant influences from biogenic secondary organic aerosol (SOA) and residential wood combustion. We observed 60% of the cloud water CHO molecular formulas to be identical to SOA samples of α-pinene, β-pinene, d-limonene, and β-caryophyllene ozonolysis. CHNO compounds had the highest number frequency and relative abundances and are associated with residential wood combustion and NOx oxidation. Multiple nitrogen atoms in the assigned molecular formulas for the nighttime cloud sample composite were observed, indicating the significance of nitrate radical reactions on the AOM composition. Several CHOS and CHNOS compounds with reduced sulfur (in addition to the commonly observed oxidized sulfur-containing compounds) were also observed; however further investigation is needed to determine the origin of the reduced sulfur-containing compounds. Overall, the molecular composition determined using ultrahigh-resolution Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry provides an unambiguous identification of the cloud water organic anion composition in the Rocky Mountain area that could help to improve the understanding of aqueous-phase processes.
Climatology of pure tropospheric profiles and column contents of ozone and carbon monoxide using MOZAIC in the mid-northern latitudes (24° N to 50° N) from 1994 to 2009
Authors: Zbinden R. M. , Thouret V. , Ricaud P. , Carminati F. , Cammas J.-P. , Nédélec P.
Published: December 2013

Abstract. The objective of this paper is to deliver the most accurate ozone (O3) and carbon monoxide (CO) climatology for the pure troposphere only, i.e. exclusively from the ground to the dynamical tropopause on an individual profile basis. The results (profiles and columns) are derived solely from the Measurements of OZone and water vapour by in-service Alrbus airCraft programme (MOZAIC) over 15 years (1994–2009). The study, focused on the northern mid-latitudes [24–50° N] and [119° W–140° E], includes more than 40 000 profiles over 11 sites to give a quasi-global zonal picture. Considering all the sites, the pure tropospheric column peak-to-peak seasonal cycle ranges are 23.7–43.2 DU for O3 and 1.7–6.9 × 10 18 molecules cm−2 for CO. The maxima of the seasonal cycles are not in phase, occurring in February–April for CO and May–July for O3. The phase shift is related to the photochemistry and OH removal efficiencies. The purely tropospheric seasonal profiles are characterized by a typical autumn–winter/spring–summer O3 dichotomy (except in Los Angeles, Eastmed – a cluster of Cairo and Tel Aviv – and the regions impacted by the summer monsoon) and a summer–autumn/winter–spring CO dichotomy. We revisit the boundary-layer, mid-tropospheric (MT) and upper-tropospheric (UT) partial columns using a~new monthly varying MT ceiling. Interestingly, the seasonal cycle maximum of the UT partial columns is shifted from summer to spring for O3 and to very early spring for CO. Conversely, the MT maximum is shifted from spring to summer and is associated with a summer (winter) MT thickening (thinning). Lastly, the pure tropospheric seasonal cycles derived from our analysis are consistent with the cycles derived from spaceborne measurements, the correlation coefficients being r=0.6–0.9 for O3 and r>0.9 for CO. The cycles observed from space are nevertheless greater than MOZAIC for O3 (by 9–18 DU) and smaller for CO (up to 1 × 10 18 molecules cm−2). The larger winter O3 difference between the two data sets suggests probable stratospheric contamination in satellite data due to the tropopause position. The study underlines the importance of rigorously discriminating between the stratospheric and tropospheric reservoirs and avoiding use of a~monthly averaged tropopause position without this strict discrimination in order to assess the pure O3 and CO tropospheric trends.
Impact of tropical land convection on the water vapour budget in the Tropical Tropopause Layer
Authors: Carminati F. , Ricaud P. , Pommereau J.-P. , Rivière E. , Khaykin S. , Attié J.-L. , Warner J.
Published: December 2013

Abstract. The tropical deep overshooting convection is known to be most intense above continental areas such as South America, Africa and the maritime continent. However, its impact on the Tropical Tropopause Layer (TTL) at global scale remains debated. In our analysis, we use the 8 yr Microwave Limb Sounder (MLS) water vapour (H2O), cloud ice water content (IWC) and temperature datasets from 2005 to date, to highlight the interplays between these parameters and their role in the water vapour variability in the TTL, separately in the northern and southern tropics. The water vapour concentration is displaying a systematic diurnal cycle with a night-time peak in the tropical Upper Troposphere (pressure ≥146 hPa) and the opposite in the TTL (121 to 68 hPa) and the tropical Lower Stratosphere (pressure ≤56 hPa), of larger amplitude above continents than continental-oceanic areas such as the maritime continent or full oceanic areas such as the Western Pacific. In addition, the amplitude of the diurnal cycle is found systematically larger (5–10%) in the southern than in the northern tropics during their respective summer, indicative of a more vigorous convective intensity in the south. Using a regional scale approach, we investigate the geographical variations of mechanisms linked to the H2O variability. In summary, the MLS water vapour, ice water cloud and temperature observations are demonstrating a clear contribution of TTL and lower stratosphere moistening by ice crystals overshooting updrafts over land tropical regions and the much greater efficiency of the process in the Southern Hemisphere.
Further evidence of important environmental information content in red-to-green ratios as depicted in paintings by great masters
Authors: Zerefos C. S. , Tetsis P. , Kazantzidis A. , Amiridis V. , Zerefos S. C. , Luterbacher J. , Eleftheratos K. , Gerasopoulos E. , Kazadzis S. , Papayannis A.
Published: December 2013

Abstract. This work is a follow-up study of a research carried out since 2005 and presents evidence supporting the findings of an earlier paper (Zerefos et al., 2007), which postulated that sunsets painted by famous artists provide independent proxy information on the aerosol optical depth after major volcanic eruptions. The series of these and additional paintings have been revisited and comparisons between coarser digital images with those derived from precision colour protocols, match together confirming the earlier results as discussed in the text. It was also found that aerosol optical depths (AODs) at 550 nm calculated by feeding Red-to-Green (R/G) ratios from a large number of paintings to a radiative transfer model, were well correlated with independent proxies from stratospheric AOD and optical extinction data, the dust veil index and others. AODs calculated from paintings have been grouped into 50 yr intervals from 1500 to 2000. From each 50 yr time period the year of the eruption and the 3 following years have been excluded. The remaining years have been termed "non-volcanic" and they provide additional evidence of a multidecadal increase in the atmospheric optical depths during the industrial "revolution". The increase of AOD at 550 nm calculated from the paintings, is estimated to range from 0.15 in the middle 19th century to about 0.20 by the end of the 20th century. To corroborate our findings, an experiment was designed in which a master painter/colourist painted successive sunsets during and after the passage of Saharan aerosols over the island of Hydra in Greece. Independent solar radiometric measurements confirmed that the master colourist's R/G ratios which were used to model his AODs, matched to the AOD values measured in situ by the co-located sunphotometers at the declining phase of the Sahara aerosol. Our work concludes that regardless of the school, red-to-green ratios from great masters can provide independent proxy AODs that correlate with widely accepted proxies and with independent measurements.
Validation of CM SAF cloud fractions: can cloud cover be reliably derived by satellite data at Hannover, Germany and Lauder, New Zealand? – a comment
Authors: Werkmeister A. , Schrempf M. , Tohsing K. , Lockhoff M. , Liley B. , Seckmeyer G.
Published: December 2013

Abstract. Cloud Fractional Cover (CFC) derived from Spinning Enhanced Visible and Infrared Imager (SEVIRI) on a geostationary satellite and from the Advanced Very High Resolution Radiometer (AVHRR) on polar orbiters, was validated against ground-based observations in Hannover, Germany (three months of data) and Lauder, New Zealand (only AVHRR, two months of data). The ground-based cloud coverage data consists of synoptical data and imagery taken by a Hemispherical Sky Imager. The standard deviation of the differences between the daily mean CFC derived by SEVIRI and synoptical data was satisfactory, but it was 100% larger than the deviations of the differences between SEVIRI and those derived by the hemispherical sky imager. For the instantaneous CFC, clear and completely overcast skies are well detected in the satellite products. During broken cloud coverage the agreement between ground-based data from the hemispherical sky imager and data from satellite is mostly uncorrelated. The standard deviations of the differences between AVHRR and the imager (instantaneous and daily mean data) were smaller than those between SEVIRI and imager. In Lauder, New Zealand, only data from the hemispherical sky imager and AVHRR was available. The standard deviations of the differences were slightly higher than in Hannover, Germany. In addition we found that the SEVIRI algorithm systematically overestimates the cloud coverage. We therefore suggest to refine the parameterization of the cloud contamination factor in the algorithms for the derivation of CFC.
Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain
Authors: Doblas-Miranda E. , Rovira P. , Brotons L. , Martínez-Vilalta J. , Retana J. , Pla M. , Vayreda J.
Published: December 2013

Abstract. Accurate estimates of C stocks and fluxes of soil organic carbon (SOC) are needed to assess the impact of climate and land use change on soil C uptake and soil C emissions to the atmosphere. Here, we present an assessment of SOC stocks in forests, shrublands and grasslands of peninsular Spain based on field measurements in more than 900 soil profiles. SOC to a depth of 1 m was modelled as a function of vegetation cover, mean annual temperature, total annual precipitation, elevation and the interaction between temperature and elevation, while latitude and longitude were used to model the correlation structure of the errors. The resulting statistical model was used to estimate SOC in the ∼8 million pixels of the Spanish Forest Map (29.3 × 106 ha). We present what we believe is the most reliable estimation of current SOC in forests, shrublands and grasslands of peninsular Spain thus far, based on the use of spatial modelling, the high number of profiles and the validity and refinement of the data layers employed. Mean concentration of SOC was 8.7 kg m−2, ranging from 2.3 kg m−2 in dry Mediterranean areas to 20.4 kg m−2 in wetter northern locations. This value corresponds to a total stock of 2.544 Tg SOC, which is four times the amount of C estimated to be stored in the biomass of Spanish forests. Climate and vegetation cover were the main variables influencing SOC, with important ecological implications for peninsular Spanish ecosystems in the face of global change. The fact that SOC was positively related to annual precipitation and negatively related to mean annual temperature suggests that future climate change predictions of increased temperature and reduced precipitation may strongly reduce the potential of Spanish soils as C sinks. However, this may be mediated by changes in vegetation cover (e.g. by favouring the development of forests associated to higher SOC values) and exacerbated by perturbations such as fire. The estimations presented here provide a baseline to estimate future changes in soil C stocks and to assess their vulnerability to key global change drivers, and should inform future actions aimed at the conservation and management of C stocks.
Spatiotemporal variability of sedimentary organic matter supply and recycling processes in coral reefs of Tayrona National Natural Park, Colombian Caribbean
Authors: Bayraktarov E. , Wild C.
Published: December 2013

Abstract. Sediments are fundamental for the functioning of oligotrophic coral reef ecosystems, because they are major places for organic matter recycling. In Tayrona National Natural Park (TNNP), Colombian Caribbean, located between the population center Santa Marta (>455 000 inhabitants) in the southwest and several river mouths in the east, coral reef sediments experience pronounced changes in environmental conditions due to seasonal coastal upwelling, but knowledge on relevant spatiotemporal effects on organic matter supply to sediments and recycling processes is not available. Therefore, sediment traps were monthly deployed over 14 months complemented by assessment of sedimentary properties and sedimentary O2 demand (SOD) at water current-exposed and -sheltered sites along distance gradients (12–20 km) to Santa Marta and the eastern river mouths (17–27 km). Findings revealed that seasonal upwelling delivered strong (75–79% of annual supply) pulses of labile organic matter mainly composed of fresh phytoplankton detritus (C : N ratio 6–8) to the seafloor. Sedimentary chlorophyll contents and SOD increased significantly with decreasing distance to the eastern rivers, but only during upwelling. This suggests sedimentary organic matter supply control by nutrient-enriched upwelling waters and riverine runoff rather than by the countercurrent-located city of Santa Marta. Organic matter pulses caused C turnover rates of 4.4% h−1 that were more than 2-fold higher at water current-exposed compared to -sheltered sites. This indicates intense advective pore water exchange and ensuing rapid recycling of the supplied labile organic matter, particularly in the highly permeable water current-exposed silicate reef sands.
The 129-Iodine content of subtropical Pacific waters: impact of Fukushima and other anthropogenic 129I sources
Authors: Guilderson T. P. , Tumey S. J. , Brown T. A. , Buesseler K. O.
Published: December 2013

Abstract. Results obtained from a dedicated radiochemistry cruise approximately 100 days after the 11 March 2011 Tohoku earthquake and subsequent disaster at the Dia'ichi Fukushima Nuclear Power Plant show that Fukushima derived radionuclides in the nearby ocean environment had penetrated, on average, to ≤250 m depth (1026.5 kg m−3 potential density surface). The excess inventory of Fukushima-derived 129I in the region (∼150 000 km2) sampled during the cruise is estimated to have been between 0.89 and 1.173 billion Bq (∼136 to ∼179 g) of 129I. Based on a tight tracer–tracer relation with 134Cs (or 137Cs) and estimates that most of the excess cesium is due to direct discharge, we infer that much of the excess 129I is from direct (non-atmospheric deposition) discharge. After taking into account oceanic transport, we estimate the direct discharge off Fukushima to have been ∼1 kg 129I. Although this small pulse is dwarfed by the ∼90 kg of weapons-testing derived 129I that was released into the environment in the late 1950s and early 1960s, it should be possible to use Fukushima derived 129I and other radionuclides (e.g., 134, 137Cs) to study transport and entrainment processes along the Kuroshio Current.
The surface temperatures of Earth: steps towards integrated understanding of variability and change
Authors: Merchant C. J. , Matthiesen S. , Rayner N. A. , Remedios J. J. , Jones P. D. , Olesen F. , Trewin B. , Thorne P. W. , Auchmann R. , Corlett G. K. , Guillevic P. C. , Hulley G. C.
Published: December 2013

Abstract. Surface temperature is a key aspect of weather and climate, but the term may refer to different quantities that play interconnected roles and are observed by different means. In a community-based activity in June 2012, the EarthTemp Network brought together 55 researchers from five continents to improve the interaction between scientific communities who focus on surface temperature in particular domains, to exploit the strengths of different observing systems and to better meet the needs of different communities. The workshop identified key needs for progress towards meeting scientific and societal requirements for surface temperature understanding and information, which are presented in this community paper. A "whole-Earth" perspective is required with more integrated, collaborative approaches to observing and understanding Earth's various surface temperatures. It is necessary to build understanding of the relationships between different surface temperatures, where presently inadequate, and undertake large-scale systematic intercomparisons. Datasets need to be easier to obtain and exploit for a wide constituency of users, with the differences and complementarities communicated in readily understood terms, and realistic and consistent uncertainty information provided. Steps were also recommended to curate and make available data that are presently inaccessible, develop new observing systems and build capacities to accelerate progress in the accuracy and usability of surface temperature datasets.
The usefulness of outcrop-analogue air-permeameter measurements for analysing aquifer heterogeneity: testing outcrop hydrogeological parameters with independent borehole data
Authors: Rogiers B. , Beerten K. , Smeekens T. , Mallants D. , Gedeon M. , Huysmans M. , Batelaan O. , Dassargues A.
Published: December 2013

Abstract. Outcropping sediments can be used as easily accessible analogues for studying subsurface sediments, especially to determine the small-scale spatial variability of hydrogeological parameters. The use of cost-effective in situ measurement techniques potentially makes the study of outcrop sediments even more attractive. We investigate to what degree air-permeameter measurements on outcrops of unconsolidated sediments can be a proxy for aquifer saturated hydraulic conductivity (K) heterogeneity. The Neogene aquifer in northern Belgium, known as a major groundwater resource, is used as the case study. K and grain-size data obtained from different outcropping sediments are compared with K and grain-size data from aquifer sediments obtained either via laboratory analyses on undisturbed borehole cores (K and grain size) or via large-scale pumping tests (K only). This comparison shows a pronounced and systematic difference between outcrop and aquifer sediments. Part of this difference is attributed to grain-size variations and earth surface processes specific to outcrop environments, including root growth, bioturbation, and weathering. Moreover, palaeoenvironmental conditions such as freezing–drying cycles and differential compaction histories will further alter the initial hydrogeological properties of the outcrop sediments. A linear correction is developed for rescaling the outcrop data to the subsurface data. The spatial structure pertaining to outcrops complements that obtained from the borehole cores in several cases. The higher spatial resolution of the outcrop measurements identifies small-scale spatial structures that remain undetected in the lower resolution borehole data. Insights in stratigraphic and K heterogeneity obtained from outcrop sediments improve developing conceptual models of groundwater flow and transport.
A global water cycle reanalysis (2003–2012) reconciling satellite gravimetry and altimetry observations with a hydrological model ensemble
Authors: van Dijk A. I. J. M. , Renzullo L. J. , Wada Y. , Tregoning P.
Published: December 2013

Abstract. We present a global water cycle reanalysis that reconciles water balance estimates derived from the GRACE satellite mission, satellite water level altimetry and off-line estimates from several hydrological models. Error estimates for the sequential data assimilation scheme were derived from available uncertainty information and the triple collocation technique. Errors in four GRACE storage products were estimated to be 11–12 mm over land areas, while errors in monthly storage changes derived from five global hydrological models were estimated to be 17–28 mm. Prior and posterior estimates were evaluated against independent observations of river water level and discharge, snow water storage and glacier mass loss. Data assimilation improved or maintained agreement overall, although results varied regionally. Uncertainties were greatest in regions where glacier mass loss and sub-surface storage decline are both plausible but poorly constrained. We calculated a global water budget for 2003–2012. The main changes were a net loss of polar ice (−341 Gt yr−1) and mountain glaciers (−185 Gt yr−1), with an additional decrease in seasonal snow pack (−19 Gt yr−1). Storage in lakes increased by +77 Gt yr−1, due to new reservoir impoundments (+87 Gt yr−1), water level change in the Caspian Sea (−27 Gt yr−1) and net increases in the remaining lakes combined (+17 Gt yr−1). There was no change in subsurface storage, because groundwater depletion (−90 Gt yr−1) was offset by increased water storage in the seasonally wet tropics of South America and southern Africa (+87 Gt yr−1), which agrees with observed and predicted changes in the tropical monsoon.
A new-type flexible rock-shed under the impact of rock block: initial experimental insights
Authors: Shi S. Q. , Wang M. , Peng X. Q. , Yang Y. K.
Published: December 2013

Abstract. A new concept of flexible rock-shed is proposed in this paper. The flexible rock-shed is made of flexible nets held up by a specially designed, steel vaulted structure. A 1:1 prototype is manufactured and tested for functional evaluation with an impact experiment. It is shown that the structure can stand for an impact energy of about 250 kJ without observable rupture of the flexible nets or cables and can be put into service again with some maintenances on the steel vaulted structure. Experimental data such as local strains, peak loads and impact times are recorded by dynamic strain gauges, load cells and a high-speed camera for structural analysis and some complementary suggestions of improving and designing are offered with respect to the joints and components. Finally, the advantages and limitations of the flexible rock-shed are outlined and the limits of the present experimental investigation and the future research for the flexible rock-shed are proposed.
Numerical simulation of relatively heavy nocturnal rain bands associated with nocturnal coastal fronts in the Mediterranean basin
Authors: Mazon J. , Pino D.
Published: December 2013

Abstract. Three offshore rain bands associated with nocturnal coastal fronts formed near the Israel coastline, the Gulf of Genoa and on the northeastern coast of the Iberian Peninsula are simulated by using version 3.3 of WRF–ARW mesoscale model to study the dynamics of the atmosphere in each case. A relatively large 1 h and 10 h accumulated precipitation are simulated when comparing with some other similar rain bands formed in the Mediterranean basin. According to the simulations, the coastal fronts formed near the Israel coastline and in the Gulf of Genoa are quasi-stationary, while the one formed on the northeastern of the Iberian Peninsula moves offshore. For the three events, the evolution of the triggering parameter H/LFC, where H is the coastal-front depth and LFC is the Level of Free Convection, is compared and used as an indication of the occurrence of convective precipitation.
The sensitivity of GNSS measurements in Fennoscandia to distinct three-dimensional upper-mantle structures
Authors: Steffen H. , Wu P.
Published: December 2013

Abstract. We present the sensitivity of Global Navigation Satellite System (GNSS) measurements at selected GNSS stations used both in the EUREF Permanent Network as well as in the BIFROST project to distinct areas in a laterally heterogeneous upper mantle beneath Fennoscandia. We therefore use a three-dimensional finite element model for glacial isostatic adjustment (GIA) calculations. The underlying structure is based on the S20A seismic tomography model, whose shear-wave velocities have been transformed into a viscosity structure of the upper mantle. Lower mantle is not investigated as previous results showed negligible sensitivity of Fennoscandian GIA data to it. We subdivide the upper mantle in four layers with lateral viscosity structure. Areas with similar viscosity within a layer are combined to larger blocks. Further subdivision is made into areas inside and outside the formerly glaciated areas. This leads to about 20 differently shaped areas per layer. We then calculate the sensitivity kernels at 10 selected GNSS stations for all blocks in comparison to a well-fitting one-dimensional GIA model. We find that GNSS stations are most sensitive to mantle viscosity in the near surrounding of the station, i.e. in the nearest about 250 km, and only within the formerly glaciated area. This area can be enlarged up to 800 km when velocities of stations in the uplift center are investigated. There is no indication of sufficiently high sensitivity of all investigated GNSS stations to regions outside the glaciated area. We also note that in the first mantle layer (70–250 km depth) below the lithosphere, there is only small sensitivity to parts along the Norwegian coast. Most prominent features in the Fennoscandian upper mantle may be detected in the second (250–450 km depth) and third layer (450–550 km depth). In future investigations on the lateral viscosity structure using GNSS measurements one should only consider GNSS stations within the area of former glaciation. They can be further grouped to address certain areas. In a combination with other GIA data, e.g. relative sea-level and gravity data, it is then highly recommended to assign more weight on those GNSS results with high sensitivity in order to determine the viscosity of a certain region.
Seasonal evolution of snow permeability under equi-temperature and temperature-gradient conditions
Authors: Domine F. , Morin S. , Brun E. , Lafaysse M. , Carmagnola C. M.
Published: December 2013

Abstract. The permeability (K) of snow to air flow affects the transfer of energy, water vapor and chemical species between the snow and the atmosphere. Yet today little is known about the temporal evolution of snow permeability as a function of metamorphic regime. Furthermore, our ability to simulate snow permeability over the seasonal evolution of a snowpack has not been tested. Here we have measured the evolution of snow permeability in a subarctic snowpack subject to high temperature-gradient (TG) metamorphism. We have also measured the evolution of the same snowpack deposited over tables so that it evolved in the equi-temperature (ET) regime. Permeability varies in the range 31 × 10−10 (ET regime) to 650 × 10−10 m2 (TG regime). Permeability increases over time in TG conditions and decreases under ET conditions. Using measurements of density ρ and of specific surface area (SSA), from which the equivalent sphere radius r is determined, we show that the equation linking SSA, density ρ and permeability, K = 3.0 r2 e(−0.013 ρ) (with K in m2, r in m and ρ in kg m−3) obtained in a previous study adequately predicts permeability values. The detailed snowpack model Crocus is used to simulate the physical properties of the TG and ET snowpacks. For the most part, all variables are well reproduced. Simulated permeabilities are up to a factor of two greater than measurements for depth hoar layers, which we attribute to snow microstructure and its aerodynamic properties. Finally, the large difference in permeabilities between ET and TG metamorphic regimes will impact atmosphere-snow energy and mass exchanges. These effects deserve consideration in predicting the effect of climate change on snow properties and snow–atmosphere interactions.
Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf
Authors: Borstad C. P. , Rignot E. , Mouginot J. , Schodlok M. P.
Published: December 2013

Abstract. Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice into the ocean, and the presently observed thinning of ice shelves is believed to be reducing their buttressing capacity and contributing to the acceleration and thinning of the grounded ice sheet. However, relatively little attention has been paid to the role that fractures play in the ability of ice shelves to sustain and transmit buttressing stresses. Here, we present a new framework for quantifying the role that fractures play in the creep deformation and buttressing capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new analytical relation for the creep of an ice shelf that accounts for the softening influence of fractures on longitudinal deformation using a state damage variable. We use this new analytical relation, combined with a temperature calculation for the ice, to partition an inverse method solution for ice shelf rigidity into independent solutions for softening damage and stabilizing backstress. Using this new approach, field and remote sensing data can be utilized to monitor the structural integrity of ice shelves, their ability to buttress the flow of ice at the grounding line, and thus their indirect contribution to ice sheet mass balance and global sea level. We apply this technique to the Larsen C ice shelf using remote sensing and Operation IceBridge data, finding damage in areas with known crevasses and rifts. Backstress is highest near the grounding line and upstream of ice rises, in agreement with patterns observed on other ice shelves. The ice in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in this area could diminish the backstress transmitted upstream. We model the consequences for the ice shelf if it loses contact with this small ice rise, finding that flow speeds would increase by 25% or more over an area the size of the former Larsen B ice shelf. Such a perturbation could potentially destabilize the northern part of Larsen C along pre-existing lines of weakness, highlighting the importance of the feedback between buttressing and fracturing in an ice shelf.
Prevalence of Cardiovascular Risk Factors among Tile and Ceramic Workers in Yazd, Iran
Authors: Mehrparvar Amir Houshang , Mirmohammadi Seyyed Jalil , Mostaghaci Mehrdad , Bahaloo Maryam , Heydari Mohammad , Samimi Ehsan , Zohal Mahnaz , Davari Mohammad Hossein
Published: December 2013

Introduction. Cardiovascular disorders (CVDs) are among the most important diseases in the world and determination of their risk factors is essential for primary and secondary prevention. This study aimed to evaluate these risk factors in workers of tile and ceramic industry, a main industry in Yazd. Materials and Methods. In a cross-sectional study, 1075 tile and ceramic workers were selected by simple sampling method. BMI, blood pressure, FBS, and lipid profile were measured and compared to international standards. Results. 731 individuals (68%) had at least one risk factor, and 52%, 12%, 3%, and 0.7% had one, two, three, and four risk factors, respectively. The most common risk factor was abnormal BMI (49.6%); low HDL (48.4%) and high TG (14.1%) were in the second and third orders. Conclusion. This study showed a relatively high prevalence for CVD risk factors among tile and ceramic workers. Low HDL, high TG, and overweight were the most frequent risk factors in this population.
Design and Development of a Littoral AUV for Underwater Target Localization and Homing Using Vision and SONAR Module
Authors: Sinha R. K. , Jha Aayush , Ahmad Faheem , Mishra Vivek , Murgai Prateek , Rustagi Vatsal , Saini Raj Kumar , Jain Akshay
Published: December 2013

This paper presents the design and development of a modular littoral autonomous underwater vehicle called “ZYRA” having six degrees of freedom for performing the following tasks underwater: target (sound sources emitting frequencies between 1 Hz and 180 KHz) localization and homing, buoy detection. The development of the AUV has been divided into, namely, five sections: mechanical design and fabrication, embedded and power systems, control and software, image processing, and underwater acoustics. A fully functional AUV has been tested in a self-created arena with different tasks spread out in a shallow water environment. Two different kinds of experimental results have been presented: first the experimental results of the SONAR module and second based on the number of successful outcomes per total number of trials for each task.
Microbial Growth in Neonatal Intravenous Fat Emulsion Administered Over 12 Versus 24 Hours
Authors: DeDonato Bethany M. , Bickford Lisa I. , Gates Ryan J.
Published: December 2013

OBJECTIVES

To determine whether an extended infusion time (24 hours) of intravenous fat emulsion is associated with an increase in microbial growth, versus a shorter infusion time (12 hours).

METHODS

Samples were collected from intravenous fat emulsions (n=132), from intravenous fat emulsions prepared in the current 24-hour infusion method (n=55), and from intravenous fat emulsions prepared in the twice-daily (12-hour infusion) method (n=55). In addition, samples were collected from pharmacy (n=22) to test for possible contamination.

RESULTS

No growth was observed in either arm of the study.

CONCLUSIONS

Current Kern Medical Center policy of preparation and administration of neonatal intensive care unit intravenous fat emulsion is safe and effective in regard to microbial growth.
A UFPA e os Anos de Chumbo: A administração do reitor Silveira Neto em tempo de ditadura (1960 - 1969)
Authors: Fontes Edilza Joana Oliveira , Alves Davidson Hugo Rocha
Published: December 2013

Este artigo tem por objetivo apresentar os primeiros anos do golpe civil-militar no Pará tendo como enfoque a Universidade Federal do Pará, entre os anos de 1960 a 1969, no mandato do reitor José da Silveira Neto e compreender, dentro do contexto específico da ditatura civil-militar, como foram os primeiros anos do regime, o debate sobre a necessidade da reforma universitária, a intervenção em algumas faculdades e os impactos do AI-5 e sua repressão a estudantes, professores e servidores públicos da UFPA após as ocupações de 68 na instituição.Palavras-chave: Ditadura Militar. Memória. AI-5. Ensino Superior. Brsil - História (1960 - 1969).
Angola: musicalidade, política e anticolonialismo (1950 - 1980)
Authors: Alves Amanda Palomo
Published: December 2013

Angola foi colônia de Portugal até 1975 e sua luta anticolonial possui importantes características no cenário africano, como: a produção literária de protesto; denúncias escritas por intelectuais; diferentes e divergentes movimentos sociais e políticos de luta pela liberdade; greves; desobediência civil; e, também, a musicalidade. Neste contexto, a música popular urbana auxiliou na construção de uma consciência nacionalista, contribuindo para a resistência e a luta anticolonial. Dessa forma, os registros fonográficos e as demais fontes coletadas e analisadas até o momento nos permitem acompanhar as transformações no conteúdo das letras das canções, que abordam temas como: cultura tradicional, resistência, luta anticolonial e a construção de um novo nacionalismo, proposto pelo governo socialista do Movimento Popular de Libertação de Angola (MPLA).Palavras-chave: Angola. Musicalidade. Anticolonialismo. Independência. MPLA.
Reversal of Domain Wall Motion in Perpendicularly Magnetized TbFeCo-Based Wires: Size Dependence
Authors: Bang Do , Awano Hiroyuki
Published: December 2013

Current-induced domain wall (DW) motion has been investigated in interfacial asymmetric SiO2/TbFeCo/Pt wires with different wire widths and thicknesses. The reversed DW motion was observed in these interfacial asymmetric wires at zero field and room temperature. This reversal of DW motion was attributed to the structural inversion asymmetry-induced spin–orbit torques (SOTs) from the Pt/TbFeCo interface and Pt layer of the wire. We found that the reversed DW velocity strongly depends on the size of wires, typically large for thin and narrow wires, suggesting that the SOTs effectively enhance the reversed DW velocity in these asymmetric TbFeCo wires.
Hydrogen Adsorption in Capped Armchair Edge (5,5) Carbon Nanotubes
Authors: Setiadi Agung , Alam Mohammad Shafiul , Muttaqien Fahdzi , Saito Mineo
Published: December 2013

We carry out first-principles calculations of the atomic hydrogen adsorption on capped armchair edge (5,5) carbon nanotubes (CNT) by using density functional theory calculations based on the spin polarized generalized gradient approximation. Based on the calculated binding energies of the hydrogen atoms, we find that the cap region is easily hydrogenated compared with the tube region. Odd numbers of hydrogen atoms induce the magnetic moment of 1 µB, whereas the even numbers of hydrogen atoms lead to nonmagnetism. Based on the energetics, we expect that the hydrogenation process is as follows: when the hydrogen atoms are adsorbed one by one, the zigzag line arrangement of the cap region is first formed, then two zigzag lines are expected to be extended to the tube region.
Reactions of surface hydrogen on amorphous carbon films with hydrogen plasma
Authors: Shinohara Masanori , Kawakami Taka-aki , Hara Ko-jiro , Yagi Shohei , Matsuda Yoshinobu , Fujiyama Hiroshi
Published: December 2013

Reactions of surface hydrocarbon components exposed to hydrogen plasma at a substrate temperature of 200 °C were investigated by in-situ infrared spectroscopy, and changes in film thickness were measured. Both the concentration of hydrocarbon components and film thickness decreased because of the hydrogen plasma exposure. The decrease in the former was larger than that in the latter. These results indicate that the abstraction effect of surface hydrogen, as well as the etching effect, was enhanced at 200 °C.
Comparable hydrogen isotopic fractionation of plant leaf wax n‐alkanoic acids in arid and humid subtropical ecosystems
Authors: Gao Li , Zheng Mei , Fraser Matthew , Huang Yongsong
Published: December 2013

Leaf wax hydrogen isotope proxies have been widely used to reconstruct past hydrological changes. However, published reconstructions have given little consideration for the potentially variable hydrogen isotopic fractionation relative to precipitation (εwax‐p) under different climate and environmental settings. Chief among various potential factors controlling fractionation is relative humidity, which is known to strongly affect oxygen isotopic ratios of plant cellulose, but its effect on hydrogen isotopic fractionation of leaf waxes is still ambiguous. Analyses of lake surface sediments and individual modern plants have provided valuable information on the variability of εwax‐p, but both approaches have significant limitations. Here, we present an alternative method to obtain the integrated, time‐resolved ecosystem‐level εwax‐p values, by analyzing modern aerosol samples collected weekly from arid (Arizona lowlands) and humid subtropical (Atlanta, Georgia) environments during the main growth season. Because aerosol samples mainly reflect regional leaf wax resources, the extreme contrast in the hydroclimate and associated vegetation assemblages between our study sites allows us to rigorously assess the impact of relative humidity and associated vegetation assemblages on leaf wax hydrogen isotopic fractionation. We show there is only minor difference (mostly <10‰) in the mean εwax‐p values in the two end‐member environments. One possible explanation is that the positive isotopic effects of low relative humidity are offset by progressive replacement of trees with grasses that have a more negative apparent fractionation. Our results represent an important step toward quantitative interpretation of leaf wax hydrogen isotopic records.
GPS constrained coseismic source and slip distribution of the 2013 Mw6.6 Lushan, China, earthquake and its tectonic implications
Authors: Jiang Zaisen , Wang Min , Wang Yanzhao , Wu Yanqiang , Che Shi , Shen Zheng‐Kang , Bürgmann Roland , Sun Jianbao , Yang Yonglin , Liao Hua , Li Qiang
Published: December 2013

The 20 April 2013 Lushan earthquake occurred on the southern section of the Longmen Shan fault system. Using GPS data from 33 continuous stations, we derive a three‐dimensional coseismic displacement field of the earthquake and invert for the location, geometry, and slip distribution of the fault rupture. Our study result indicates that the earthquake occurred on a reverse fault striking N28°E and dipping 43° to the NW, with the maximum slip located at 30.292°N, 102.943°E, and 13 km depth. The rupture is dominated by thrust faulting, with a slight but still statistically significant sinistral component. The seismic moment release is 9.5 × 1018 N · m, equivalent to a Mw6.6 earthquake. Our results suggest that at the southern end of the Longmen Shan fault zone near the triple junction with the Xianshuihe and Anninghe faults, the kinematic deformation field is no longer block‐like, but broadly distributed to accommodate the buttressing effect of deformation around the fault triple junction.
Ion gyroharmonic structures in stimulated radiation during second electron gyroharmonic heating: 2. Simulations
Authors: Samimi A. , Scales W. A. , Bernhardt P. A. , Briczinski S. J. , McCarrick M. J.
Published: December 2013

Characteristics of the Stimulated Electromagnetic Emission (SEE) spectrum recorded during ionospheric heating near the second electron gyroharmonic frequency, 2fce, have attracted attention due to their possible connection to artificially generated airglow and artificial ionospheric layers. Two newly discovered SEE spectral features within 1 kHz frequency shift relative to the pump frequency are (1) discrete narrowband structures ordered by the local ion gyrofrequency involving parametric decay of the pump field into upper hybrid/electron Bernstein (UH/EB) and ion Bernstein (IB) waves and (2) broadband structures that maximize around 500 Hz downshifted relative to the pump frequency involving parametric decay of the pump field into upper hybrid/electron Bernstein and oblique ion acoustic (IA) waves [Samimi et al., 2013]. In this paper, a two‐dimensional particle‐in‐cell Monte Carlo Collision computational model is employed in order to consider nonlinear aspects such as (1) electron acceleration through wave‐particle interaction, (2) more complex nonlinear wave‐wave processes, and (3) temporal evolution of irregularities through nonlinear saturation. The simulation results show that the IB‐associated parametric decay is primarily associated with electron acceleration perpendicular to the geomagnetic field. More gyroharmonic lines are typically associated with more electron acceleration. Electron acceleration is reduced when the pump frequency is sufficiently close to 2fce. The IA‐associated parametric decay instability is primarily associated with electron tail heating along the magnetic field and electron acceleration is reduced when the pump frequency is sufficiently close to 2fce. Characteristics of caviton collapse behavior become prevalent in this case. Results are discussed within the context of some recent experimental observations.
Active fires from the Suomi NPP Visible Infrared Imaging Radiometer Suite: Product status and first evaluation results
Authors: Csiszar Ivan , Schroeder Wilfrid , Giglio Louis , Ellicott Evan , Vadrevu Krishna P. , Justice Christopher O. , Wind Brad
Published: December 2013

The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor on the Suomi National Polar‐orbiting Partnership (S‐NPP) satellite incorporates fire‐sensitive channels, including a dual‐gain high‐saturation temperature 4 µm channel, enabling active fire detection and characterization. The active fire product, based on the 750 m moderate resolution “M” bands of VIIRS, is one of the standard operational products generated by the Interface Data Processing Segment of the S‐NPP ground system. The product builds on an earlier “Collection 4” version of the algorithm used for processing Moderate Resolution Imaging Spectroradiometer (MODIS) data. Following postlaunch quality assessments and corrections in the input VIIRS Sensor Data Record data processing, an initial low detection bias was removed and the product achieved Beta quality in April 2012. Daily spurious detections along‐scan lines were also significantly reduced as a result of further processing improvements in October 2012. Direct product comparison with MODIS over 4 months of data in 2013 has shown that VIIRS produces approximately 26% more detections than MODIS within the central 3 pixel VIIRS aggregation zone of approximately ±31° scan angle range and 70% more detections outside of that zone, mainly as a result of the superior VIIRS scanning and sampling characteristics. Further development is in progress to ensure high‐quality VIIRS fire products that continue the MODIS data record and better serve the user community by delivering a full image classification product and fire radiative power retrievals. Research is also underway to take advantage of the radiometric signal from the 375 m VIIRS imager “I” bands.
Hierarchical Growth of Fluorescent Dye Aggregates in Water by Fusion of Segmented Nanostructures
Authors: Zhang Xin , Görl Daniel , Stepanenko Vladimir , Würthner Frank
Published: December 2013

Dye aggregates are becoming increasingly attractive for diverse applications, in particular as organic electronic and sensor materials. However, the growth processes of such aggregates from molecular to small assemblies up to nanostructures is still not properly understood, limiting the design of materials’ functional properties. Here we elucidate the supramolecular growth process for an outstanding class of functional dyes, perylene bisimides (PBIs), by transmission electron microscopy (TEM), cryogenic scanning electron microscopy (cryo‐SEM), and atomic force microscopy (AFM). Our studies reveal a sequential growth of amphiphilic PBI dyes from nanorods into nanoribbons in water by fusion and fission processes. More intriguingly, the fluorescence observed for higher hierarchical order nanoribbons was enhanced relative to that of nanorods. Our results provide insight into the relationship between molecular, morphological, and functional properties of self‐assembled organic materials.