bluuebunny/crossref_metadata_2025 huggingface dataset:
A two stage Bayesian stochastic optimization model for cascaded hydropower systems considering varying uncertainty of flow forecasts
Authors: Xu Wei , Zhang Chi , Peng Yong , Fu Guangtao , Zhou Huicheng
Published: October 2014

This paper presents a new Two Stage Bayesian Stochastic Dynamic Programming (TS‐BSDP) model for real time operation of cascaded hydropower systems to handle varying uncertainty of inflow forecasts from Quantitative Precipitation Forecasts. In this model, the inflow forecasts are considered as having increasing uncertainty with extending lead time, thus the forecast horizon is divided into two periods: the inflows in the first period are assumed to be accurate, and the inflows in the second period assumed to be of high uncertainty. Two operation strategies are developed to derive hydropower operation policies for the first and the entire forecast horizon using TS‐BSDP. In this paper, the newly developed model is tested on China's Hun River cascade hydropower system and is compared with three popular stochastic dynamic programming models. Comparative results show that the TS‐BSDP model exhibits significantly improved system performance in terms of power generation and system reliability due to its explicit and effective utilization of varying degrees of inflow forecast uncertainty. The results also show that the decision strategies should be determined considering the magnitude of uncertainty in inflow forecasts. Further, this study confirms the previous finding that the benefit in hydropower generation gained from the use of a longer horizon of inflow forecasts is diminished due to higher uncertainty and further reveals that the benefit reduction can be substantially mitigated through explicit consideration of varying magnitudes of forecast uncertainties in the decision‐making process.
Relationships between stream nitrate concentration and spatially distributed snowmelt in high‐elevation catchments of the western U.S.
Authors: Perrot Danielle , Molotch Noah P. , Williams Mark W. , Jepsen Steven M. , Sickman James O.
Published: October 2014

This study compares stream nitrate (
) concentrations to spatially distributed snowmelt in two alpine catchments, the Green Lakes Valley, Colorado (GLV4) and Tokopah Basin, California (TOK). A snow water equivalent reconstruction model and Landsat 5 and 7 snow cover data were used to estimate daily snowmelt at 30 m spatial resolution in order to derive indices of new snowmelt areas (NSAs). Estimates of NSA were then used to explain the
flushing behavior for each basin over a 12 year period (1996–2007). To identify the optimal method for defining NSAs and elucidate mechanisms underlying catchment
flushing, we conducted a series of regression analyses using multiple thresholds of snowmelt based on temporal and volumetric metrics. NSA indices defined by volume of snowmelt (e.g., snowmelt ≤ 30 cm) rather than snowmelt duration (e.g., snowmelt ≤ 9 days) were the best predictors of stream
concentrations. The NSA indices were better correlated with stream
concentration in TOK (average R2= 0.68) versus GLV4 (average R2= 0.44). Positive relationships between NSA and stream
concentration were observed in TOK with peak stream
concentration occurring on the rising limb of snowmelt. Positive and negative relationships between NSA and stream
concentration were found in GLV4 with peak stream
concentration occurring as NSA expands. Consistent with previous works, the contrasting
flushing behavior suggests that streamflow in TOK was primarily influenced by overland flow and shallow subsurface flow, whereas GLV4 appeared to be more strongly influenced by deeper subsurface flow paths.
Synthesizing Studies of Dam Removal
Authors: O'Connor Jim , East Amy
Published: October 2014

Dam decommissioning is rapidly emerging as an important river restoration strategy in the United States. Hundreds of dams have been removed in the past few decades, including several large ones (>10–15 meters) impounding large sediment volumes (>106 cubic meters) in the past 3 years, notably Condit Dam and the Elwha River dams in Washington State. These removals and the associated studies provide for the first time an opportunity to evaluate the immediate and persistent consequences of these significant fluvial—and in some cases, coastal—perturbations. Understanding dam removal response not only improves understanding of landscape and ecosystem adjustment to profound sediment pulses but also provides important lessons for future watershed restoration efforts.
Regionalized global budget of the CO2 exchange at the air‐water interface in continental shelf seas
Authors: Laruelle Goulven G. , Lauerwald Ronny , Pfeil Benjamin , Regnier Pierre
Published: October 2014

Over the past decade, estimates of the atmospheric CO2 uptake by continental shelf seas were constrained within the 0.18–0.45 Pg C yr−1 range. However, most of those estimates are based on extrapolations from limited data sets of local flux measurements (n < 100). Here we propose to derive the CO2 air‐sea exchange of the shelf seas by extracting 3 · 106 direct surface ocean CO2 measurements from the global database SOCAT (Surface Ocean CO2 Atlas), atmospheric CO2 values from GlobalVIEW and calculating gas transfer rates using readily available global temperature, salinity, and wind speed fields. We then aggregate our results using a global segmentation of the shelf in 45 units and 152 subunits to establish a consistent regionalized CO2 exchange budget at the global scale. Within each unit, the data density determines the spatial and temporal resolutions at which the air‐sea CO2 fluxes are calculated and range from a 0.5° resolution in the best surveyed regions to a whole unit resolution in areas where data coverage is limited. Our approach also accounts, for the first time, for the partial sea ice cover of polar shelves. Our new regionalized global CO2 sink estimate of 0.19 ± 0.05 Pg C yr−1 falls in the low end of previous estimates. Reported to an ice‐free surface area of 22 · 106 km2, this value yields a flux density of 0.7 mol C m−2 yr−1, ~40% more intense than that of the open ocean. Our results also highlight the significant contribution of Arctic shelves to this global CO2 uptake (0.07 Pg C yr−1).
The surf zone heat budget: The effect of wave heating
Authors: Sinnett Gregory , Feddersen Falk
Published: October 2014

Surf zone incident wave energy flux is dissipated by wave breaking which through viscosity generates heat. This effect is not present in shelf heat budgets and has not previously been considered. Pier‐based observations of water temperature in 1–4 m depth, meteorology, and waves are used to test a surf zone heat budget, which closes on diurnal and longer time scales. Wave energy flux is the second most variable term with mean contribution one fourth of the mean short‐wave radiation. The heat budget residual has semidiurnal and higher‐frequency variability and net cooling. Cross‐shore advective heat flux driven by internal wave events, rip currents, and undertow contribute to this residual variability and net cooling. In locations with large waves, steeper beaches, or less solar radiation, the ratio of wave energy flux to short‐wave radiation may be >1.
New lava lake at Nyamuragira volcano revealed by combined ASTER and OMI SO2 measurements
Authors: Campion Robin
Published: October 2014

We report recent satellite measurements of the SO2 emissions from the Virunga Volcanic Group (VVG), which comprises the very active Nyamuragira and Nyiragongo volcanoes. Combining high time resolution data from the UV‐operating OMI (Ozone Monitoring Instrument) with high ground resolution data from the IR‐operating ASTER (Advanced Spaceborne Thermal Emission and Reflection radiometer), we show that (1) the SO2 emissions from the VVG have increased severalfold since the end of the last eruption of Nyamuragira. (2) Nyamuragira, which used to have very low intereruptive emissions of SO2 before this eruption, is now contributing to 60 to 90% of the combined emissions measured by OMI. Considering the eruptive history of Nyamuragira, the evidence from previous research for the existence of a shallow magma chamber, and the detection of isolated thermal anomalies since April 2014, we conclude that a deep‐seated lava lake has formed in the N pit of Nyamuragira's caldera.
Satellite nighttime lights reveal increasing human exposure to floods worldwide
Authors: Ceola Serena , Laio Francesco , Montanari Alberto
Published: October 2014

River floods claim thousands of lives every year, but effective and high‐resolution methods to map human exposure to floods at the global scale are still lacking. We use satellite nightlight data to prove that nocturnal lights close to rivers are consistently related to flood damages. We correlate global data of economic losses caused by flooding events with nighttime lights and find that increasing nightlights are associated to flood damage intensification. Then, we analyze the temporal evolution of nightlights along the river network all over the world from 1992 to 2012 and obtain a global map of nightlight trends, which we associate with increasing human exposure to floods, at 1 km2 resolution. An enhancement of exposure to floods worldwide, particularly in Africa and Asia, is revealed, which may exacerbate the projected effects of climate change on flood‐related losses and therefore argues for the development of valuable flood preparedness and mitigation strategies.
A statistical analysis of heliospheric plasma sheets, heliospheric current sheets, and sector boundaries observed in situ by STEREO
Authors: Liu Y. C.‐M. , Huang J. , Wang C. , Klecker B. , Galvin A. B. , Simunac K. D. C. , Popecki M. A. , Kistler L. , Farrugia C. , Lee M. A. , Kucharek H , Opitz A. , Luhmann J. G. , Jian Lan
Published: October 2014

The heliocentric orbits of STEREO A and B with a separation in longitude increasing by about 45° per year provide the unique opportunity to study the evolution of the heliospheric plasma sheet (HPS) on a time scale of up to ~2 days and to investigate the relative locations of HPSs and heliospheric current sheets (HCSs). Previous work usually determined the HCS locations based only on the interplanetary magnetic field. A recent study showed that a HCS can be taken as a global structure only when it matches with a sector boundary (SB). Using magnetic field and suprathermal electron data, it was also shown that the relative location of HCS and SB can be classified into five different types of configurations. However, only for two out of these five configurations, the HCS and SB are located at the same position and only these will therefore be used for our study of the HCS/HPS relative location. We find that out of 37 SBs in our data set, there are 10 suitable HPS/HCS event pairs. We find that an HPS can either straddle or border the related HCS. Comparing the corresponding HPS observations between STEREO A and B, we find that the relative HCS/HPS locations are mostly similar. In addition, the time difference of the HPSs observations between STEREO A and B match well with the predicted time delay for the solar wind coming out of a similar region of the Sun. We therefore conclude that HPSs are stationary structures originating at the Sun.
A methodology for near‐field tsunami inundation forecasting: Application to the 2011 Tohoku tsunami
Authors: Gusman Aditya Riadi , Tanioka Yuichiro , MacInnes Breanyn T. , Tsushima Hiroaki
Published: October 2014

Existing tsunami early warning systems in the world can give either one or a combination of estimated tsunami arrival times, heights, or qualitative tsunami forecasts before the tsunami hits near‐field coastlines. A future tsunami early warning system should be able to provide a reliable near‐field tsunami inundation forecast on high‐resolution topography within a short time period. Here we describe a new methodology for near‐field tsunami inundation forecasting. In this method, a precomputed tsunami inundation and precomputed tsunami waveform database is required. After information about a tsunami source is estimated, tsunami waveforms at nearshore points can be simulated in real time. A scenario that gives the most similar tsunami waveforms is selected as the site‐specific best scenario and the tsunami inundation from that scenario is selected as the tsunami inundation forecast. To test the algorithm, tsunami inundation along the Sanriku Coast is forecasted by using source models for the 2011 Tohoku earthquake estimated from GPS, W phase, or offshore tsunami waveform data. The forecasting algorithm is capable of providing a tsunami inundation forecast that is similar to that obtained by numerical forward modeling but with remarkably smaller CPU time. The time required to forecast tsunami inundation in coastal sites from the Sendai Plain to Miyako City is approximately 3 min after information about the tsunami source is obtained. We found that the tsunami inundation forecasts from the 5 min GPS, 5 min W phase, 10 min W phase fault models, and 35 min tsunami source model are all reliable for tsunami early warning purposes and quantitatively match the observations well, although the latter model gives tsunami forecasts with highest overall accuracy. The required times to obtain tsunami forecast from the above four models are 8 min, 9 min, 14 min, and 39 min after the earthquake, respectively, or in other words 3 min after receiving the source model. This method can be useful in developing future tsunami forecasting systems with a capability of providing tsunami inundation forecasts for locations near the tsunami source area.
Hygroscopic behavior of water‐soluble matter extracted from biomass burning aerosols collected at a rural site in Tanzania, East Africa
Authors: Boreddy S. K. R. , Kawamura Kimitaka , Mkoma Stelyus , Fu Pingqing
Published: October 2014

In this study, we present the hygroscopic behavior of water‐soluble matter (WSM) extracted from biomass burning derived particulate matter 2.5 (PM2.5) aerosols collected at a rural background site in Tanzania during June–August 2011. Hygroscopic growth factors,g(RH), of WSM were measured by hygroscopic tandem differential mobility analyzer (H‐TDMA) with an initial dry particle diameter of 100 nm. We observed that theg(RH) of WSM at 90% relative humidity (RH),g(90%)WSM, ranged from 1.10 to 1.47 with an average of 1.25 ± 0.12. The H‐TDMA retrieved hygroscopicity parameter of WSM,κWSM, ranged from 0.04 to 0.24 with a mean of 0.11 ± 0.07. We found that the observedg(90%)WSMis positively correlated with PM2.5mass fractions of K+(R2 = 0.61), Cl−(0.54), and organic carbon (0.58). Moreover, it well correlates with levoglucosan (0.67) and total diacids (0.76), implying that although the inorganic fraction may be the most important factor to control the hygroscopicity; biomass burning organics play a significant role in the hygroscopicity of Tanzanian aerosols. The lower growth factors obtained over the sampling site are probably due to the formation of less water‐soluble potassium oxalate (K2C2O4) or less hygroscopic K2SO4particles during atmospheric aging. We observed a moderate correlation (R2 = 0.33) between PM2.5mass fraction of WSOC andg(90%)WSM. The retrievedg(90%)WSOMvalues ranged from 1.0 to 1.25 with a mean of 1.16 ± 0.05. This study demonstrates that the hygroscopicity of Tanzanian aerosols is largely controlled by the emission of biomass burning products and the subsequent chemical aging during atmospheric transport.
Suppression in droplet growth kinetics by the addition of organics to sulfate particles
Authors: Wong Jenny P. S. , Liggio John , Li Shao‐Meng , Nenes Athanasios , Abbatt Jonathan P. D.
Published: October 2014

Aerosol‐cloud interactions are affected by the rate at which water vapor condenses onto particles during cloud droplet growth. Changes in droplet growth rates can impact cloud droplet number and size distribution. The current study investigated droplet growth kinetics of acidic and neutral sulfate particles which contained various amounts and types of organic compounds, from model compounds (carbonyls) to complex mixtures (α‐pinene secondary organic aerosol and diesel engine exhaust). In most cases, the formed droplet size distributions were shifted to smaller sizes relative to control experiments (pure sulfate particles), due to suppression in droplet growth rates in the cloud condensation nuclei counter. The shift to smaller droplets correlated with increasing amounts of organic material, with the largest effect observed for acidic seed particles at low relative humidity. For all organics incorporated onto acidic particles, formation of high molecular weight compounds was observed, probably by acid‐catalyzed Aldol condensation reactions in the case of carbonyls. To test the reversibility of this process, carbonyl experiments were conducted with acidic particles exposed to higher relative humidity. High molecular weight compounds were not measured in this case and no shift in droplet sizes was observed, suggesting that high molecular weight compounds are the species affecting the rate of water uptake. While these results provide laboratory evidence that organic compounds can slow droplet growth rates, the modeled mass accommodation coefficient of water on these particles (α > 0.1) indicates that this effect is unlikely to significantly affect cloud properties, consistent with infrequent field observations of slower droplet growth rates.
Advanced meteor radar installed at Tirupati: System details and comparison with different radars
Authors: Rao S. Vijaya Bhaskara , Eswaraiah S. , Venkat Ratnam M. , Kosalendra E. , Kishore Kumar K. , Sathish Kumar S. , Patil P. T. , Gurubaran S.
Published: October 2014

An advanced meteor radar, viz, Sri Venkateswara University (SVU) meteor radar (SVU MR) operating at 35.25 MHz, was installed at Sri Venkateswara University (SVU), Tirupati (13.63°N, 79.4°E), India, in August 2013 for continuous observations of horizontal winds in the mesosphere and lower thermosphere (MLT). This manuscript describes the purpose of the meteor radar, system configuration, measurement techniques, its data products, and operating parameters, as well as a comparison of measured mean winds in the MLT with contemporary radars over the Indian region. It is installed close to the Gadanki (13.5°N, 79.2°E) mesosphere‐stratosphere‐troposphere (MST) radar to fill the region between 85 and 100 km where this radar does not measure winds. The present radar provides additional information due to its high meteor detection rate, which results in accurate wind information from 70 to 110 km. As a first step, we made a comparison of SVU MR‐derived horizontal winds in the MLT region with those measured by similar and different (MST and MF radars) techniques over the Indian region, as well as model (horizontal wind model 2007) data sets. The comparison showed an exquisite agreement between the overlapping altitudes (82–98 km) of different radars. Zonal winds compared very well, as did the meridional winds. The observed discrepancies and limitations in the wind measurement are discussed in the light of different measuring techniques and the effects of small‐scale processes like gravity waves. This new radar is expected to play an important role in our understanding of the vertical and lateral coupling of different regions of the atmosphere that will be possible when measurements from nearby locations are combined.
Greenhouse gas profiling by infrared‐laser and microwave occultation in cloudy air: Results from end‐to‐end simulations
Authors: Proschek V. , Kirchengast G. , Emde C. , Schweitzer S.
Published: October 2014

The new mission concept of microwave and infrared‐laser occultation between Low Earth Orbit satellites (LMIO) is capable to provide accurate, consistent, and long‐term stable measurements of many essential climate variables. These include temperature, humidity, key greenhouse gases (GHGs) such as carbon dioxide and methane, and line of sight wind speed, all with focus on profiling the upper troposphere and lower stratosphere. The GHG retrieval performance from LMIO data was so far analyzed under clear‐air conditions only, without clouds and scintillations from turbulence. Here we present and evaluate an algorithm, built into an already published clear‐air algorithm, which copes with cloud and scintillation influences on the infrared‐laser transmission profiles used for GHG retrieval. We find that very thin ice clouds fractionally extinct the infrared‐laser signals, thicker but broken ice clouds block them over limited altitude ranges, and liquid water clouds generally block them so that their cloud top altitudes typically constitute the limit to tropospheric penetration of profiles. The advanced algorithm penetrates through broken cloudiness. It achieves this by producing a cloud flagging profile from cloud‐perturbed infrared‐laser signals, which then enables bridging of transmission profile gaps via interpolation. Evaluating the retrieval performance with quasi‐realistic end‐to‐end simulations, including high‐resolution cloud data and scintillations from turbulence, we find a small increase only of GHG retrieval RMS errors due to broken‐cloud scenes and the profiles remain essentially unbiased as in clear air. These results are encouraging for future LMIO implementation, indicating that GHG profiles can be retrieved through broken cloudiness, maximizing upper troposphere coverage.
Freshwater lenses as archive of climate, groundwater recharge, and hydrochemical evolution: Insights from depth‐specific water isotope analysis and age determination on the island of Langeoog, Germany
Authors: Houben Georg J. , Koeniger Paul , Sültenfuß Jürgen
Published: October 2014

The age stratification of a freshwater lens on the island of Langeoog, Germany, was reconstructed through depth‐specific sampling and groundwater dating using the tritium‐helium method. The stratification is strongly affected by the land use and resulting differences in recharge rates. Infiltration at the dune tops is significantly lower than in the valleys, due to repellency of the dry sand. Dune valleys contribute up to four times more groundwater recharge per area than other areas. Housing development in dune areas might therefore significantly decrease the available fresh groundwater. The freshwater column shows a distinct increase of stable isotope values with decreasing depths. Hence, the freshwater lens contains a climate archive which reflects changing environmental conditions at the time of recharge. Combined with tritium‐helium dating, this pattern could be matched to climate records which show an increase of the temperature at the time of recharge and rainfall rates during the last 50 years. The spatial and temporal developments of water chemistry during the passage through the lens follow a marked pattern from a sodium and chloride‐dominated rainwater of low conductivity to a more mineralized sodium bicarbonate water type, caused by dissolution of carbonate shells close to the surface and subsequent ion exchange of calcium for sodium in the deeper parts.
The concept of dual‐boundary forcing in land surface‐subsurface interactions of the terrestrial hydrologic and energy cycles
Authors: Rahman M. , Sulis M. , Kollet S. J.
Published: October 2014

Terrestrial hydrological processes interact in a complex, nonlinear fashion. It is important to quantify these interactions to understand the overall mechanisms of the coupled water and energy cycles. In this study, the concept of a dual‐boundary forcing is proposed that connects the variability of atmospheric (upper boundary) and subsurface (lower boundary) processes to the land surface mass and energy balance components. According to this concept, the space‐time patterns of land surface mass and energy fluxes can be explained by the variability of the dominating boundary condition for the exchange processes, which is determined by moisture and energy availability. A coupled subsurface‐land surface model is applied on the Rur catchment, Germany, to substantiate the proposed concept. Spectral and geostatistical analysis on the observations and model results show the coherence of different processes at various space‐time scales in the hydrological cycle. The spectral analysis shows that atmospheric radiative forcing generally drives the variability of the land surface energy fluxes at the daily time scale, while influence of subsurface hydrodynamics is significant at monthly to multimonth time scales under moisture‐limited conditions. The geostatistical analysis demonstrates that atmospheric forcing and groundwater control the spatial variability of land surface processes under energy and moisture‐limited conditions, respectively. These results suggest that under moisture‐limited conditions, groundwater influences the variability of the land surface mass and energy fluxes. Under energy‐limited conditions, on the contrary, variability of land surface processes can be explained by atmospheric forcing alone.
Dual‐domain mass‐transfer parameters from electrical hysteresis: Theory and analytical approach applied to laboratory, synthetic streambed, and groundwater experiments
Authors: Briggs Martin A. , Day‐Lewis Frederick D. , Ong John B. , Harvey Judson W. , Lane John W.
Published: October 2014

Models of dual‐domain mass transfer (DDMT) are used to explain anomalous aquifer transport behavior such as the slow release of contamination and solute tracer tailing. Traditional tracer experiments to characterize DDMT are performed at the flow path scale (meters), which inherently incorporates heterogeneous exchange processes; hence, estimated “effective” parameters are sensitive to experimental design (i.e., duration and injection velocity). Recently, electrical geophysical methods have been used to aid in the inference of DDMT parameters because, unlike traditional fluid sampling, electrical methods can directly sense less‐mobile solute dynamics and can target specific points along subsurface flow paths. Here we propose an analytical framework for graphical parameter inference based on a simple petrophysical model explaining the hysteretic relation between measurements of bulk and fluid conductivity arising in the presence of DDMT at the local scale. Analysis is graphical and involves visual inspection of hysteresis patterns to (1) determine the size of paired mobile and less‐mobile porosities and (2) identify the exchange rate coefficient through simple curve fitting. We demonstrate the approach using laboratory column experimental data, synthetic streambed experimental data, and field tracer‐test data. Results from the analytical approach compare favorably with results from calibration of numerical models and also independent measurements of mobile and less‐mobile porosity. We show that localized electrical hysteresis patterns resulting from diffusive exchange are independent of injection velocity, indicating that repeatable parameters can be extracted under varied experimental designs, and these parameters represent the true intrinsic properties of specific volumes of porous media of aquifers and hyporheic zones.
Pore scale dynamics underlying the motion of drainage fronts in porous media
Authors: Moebius Franziska , Or Dani
Published: October 2014

Fluid displacement fronts in porous media exhibit a peculiar duality; the seemingly regular macroscopic motion of the front is propelled by numerous and irregular pore scale interfacial jumps. These pore scale events shape emergent front morphology, affect phase entrapment behind a front, and are likely important for colloidal mobilization and solute dispersion at the front. We present an experimental study focusing on drainage fluid front invasion dynamics through sintered glass beads using a high‐speed camera and rapid capillary pressure measurements to resolve pore scale invasion events over a wide range of boundary conditions (flow rates and gravitational influences). We distinguished three types of “pores”: geometrical pores deduced from image analyses; individual pore invasion volumes imaged during displacement; and pore volumes deduced from capillary pressure fluctuations during constant withdrawal rates. The resulting pore volume distributions were remarkably similar for slow drainage rates. Invaded pore volumes were not affected by gravitational forces, however with increased viscous forces (higher displacement rates) the fraction of small invaded volumes increased. Capillary pressure fluctuations were exponentially distributed in agreement with findings from previous studies. The distribution of pressure fluctuations exhibited a distinct cutoff concurrent with the onset of simultaneous invasion events. The study highlights the different manifestation of “pores” and their sensitivity to external (macroscopic) boundary conditions. The remarkable similarity of geometrical and pressure‐deduced pore spaces offers opportunities for deducing pore size distribution dynamically.
My Journey from Research to Impact: Long Road and Much Traffic
Authors: Memon Amina
Published: October 2014

In this article, Amina Memon discusses some of the highlights of her career in applied cognitive and social psychology including those who inspired her. Copyright © 2014 John Wiley & Sons, Ltd.
Metal–Ceramic Layered Materials and Composites Manufactured Using Powder Techniques
Authors: Slawik Tim , Bergner Anne , Puschmann Roberto , Franke Peter , Raethel Jan , Behnisch Thomas , Scholl Roland , Berger Lutz‐Michael , Moritz Tassilo , Zelm Roland , Gude Maik , Michaelis Alexander , Beyer Eckhard , Leyens Christoph , Großmann Harald , Kieback Bernd
Published: October 2014

The manufacturing of metal–ceramic composites was investigated as part of subproject “C3–CerMetComp” at the ECEMP Excellence Cluster in Dresden. Three different manufacturing technologies were investigated: (i) Thermal spraying for the preparation of metal–ceramic multilayers; (ii) tape casting of layered composites followed by a co‐sintering step (in order to prevent defects during co‐sintering the sintering behavior of the metallic material was adjusted to the shrinkage behavior of the ceramic); and (iii) hot pressing of zirconia‐metal fiber composites with homogenously distributed fibers and subsequent evaluation by means of fracture toughness testing.
How Absorbed Hydrogen Affects the Catalytic Activity of Transition Metals
Authors: Aleksandrov Hristiyan A. , Kozlov Sergey M. , Schauermann Swetlana , Vayssilov Georgi N. , Neyman Konstantin M.
Published: October 2014

Heterogeneous catalysis is commonly governed by surface active sites. Yet, areas just below the surface can also influence catalytic activity, for instance, when fragmentation products of catalytic feeds penetrate into catalysts. In particular, H absorbed below the surface is required for certain hydrogenation reactions on metals. Herein, we show that a sufficient concentration of subsurface hydrogen, Hsub, may either significantly increase or decrease the bond energy and the reactivity of the adsorbed hydrogen, Had, depending on the metal. We predict a representative reaction, ethyl hydrogenation, to speed up on Pd and Pt, but to slow down on Ni and Rh in the presence of Hsub, especially on metal nanoparticles. The identified effects of subsurface H on surface reactivity are indispensable for an atomistic understanding of hydrogenation processes on transition metals and interactions of hydrogen with metals in general.
Smart carboxymethylchitosan hydrogels that have thermo‐ and pH‐responsive properties
Authors: Rodkate Nantharak , Rutnakornpituk Boonjira , Wichai Uthai , Ross Gareth , Rutnakornpituk Metha
Published: October 2014

Thermo‐responsive poly(N‐isopropylacrylamide) (poly(NIPAAm)) and pH‐responsive poly(N,N′‐diethylaminoethyl methacrylate) (poly(DEAEMA)) polymers were grafted to carboxymethylchitosan (CMC) via radical polymerization to form highly water swellable hydrogels with dual responsive properties. Ratios of CMC, NIPAAm to DEAEMA used in the reactions were finely adjusted such that the thermo and pH responsiveness of the hydrogels was retained. Scanning electron microscopy (SEM) indicated the formation of an internal porous structure for the swollen CMC hydrogels upon incorporation of poly(NIPAAm) and poly(DEAEMA). Effect of temperature and pH changes on water swelling properties of the hydrogels was investigated. It was found that the water swelling of the hydrogels was enhanced when the solution pH was under basic conditions (pH 11) or the temperature was below its lower critical solution temperature (LCST). These responsive properties can be used to regulate releasing rate of an entrapped drug from the hydrogels, a model drug, indomethacin was used to demonstrate the release. These smart and nontoxic CMC‐based hydrogels show great potential for use in controlled drug release applications with controllable on‐off switch properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41505.
Chemical modification of gum arabic and its application in the encapsulation of Cymbopogon citratus essential oil
Authors: Ribeiro Francisco Wanderson Moreira , Laurentino Larissa da Silva , Alves Carlucio Roberto , Bastos Maria do Socorro Rocha , Costa José Maria Correia da , Canuto Kirley Matos , Furtado Roselayne Ferro
Published: October 2014

Sodium trimetaphosphate (STMP) is an effective crosslinking agent of starch and can be used in other polysaccharides for promoting changes in their physical and chemical characteristics. In this study, gum arabic was modified with different STMP concentrations and evaluated as the changes in the physical and physicochemical characteristics. Further, modified gum arabic was evaluated by encapsulation efficiency (EE) of Cymbopogon citratus essential oil. A lower viscosity was observed with the increase of the STMP concentration. Higher concentrations of STMP decreased the water amount retained in the modified gum arabic. The increasing of the crosslinking degree causes a decrease in particle size. The EE of modified gum arabic with 6% STMP was 97%, whereas for the unmodified gum arabic was 85%. The high efficiency encapsulation of the essential oil is a positive result of physicochemical changes in the gum arabic crosslinking. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41519.
Visible‐Light‐Responsive Multielectron Redox Catalysis of Lacunary Polyoxometalates Induced by Substrate Coordination to Their Lacuna
Authors: Suzuki Kosuke , Jeong Jinu , Yamaguchi Kazuya , Mizuno Noritaka
Published: October 2014

We describe herein the efficient visible‐light‐responsive polyoxometalate‐based multielectron photoredox catalysis induced by in situ coordination of alcohols to the lacuna of TBA4H4[γ‐SiW10O36] (I, TBA=tetra‐n‐butylammonium). The coordination of alcohols to the lacuna of I generated a new highest occupied molecular orbital as the electron donor level and enabled the visible‐light‐responsive multielectron transfer from alcohols to I, which could be utilized for aerobic alcohol oxidation and one‐pot synthesis of N‐arylimines starting from nitroarenes and primary alcohols.
Smad‐induced alterations of matrix metabolism by a myristoyl tetra peptide
Authors: Kwon Haeyoung , Lee Yun Sub , Kim Myung Ok , Chang Min Youl , Won Bo Mi , Jin Byung Suk , Park Seyeon
Published: October 2014

Regulation of extracellular matrix (ECM) components is essential for tissue homeostasis and function. We screened a small peptide that induces ECM protein synthesis for its usefulness in protecting keratinocytes. In this report, we demonstrate that myristoyl tetrapeptide Ala‐Ala‐Pro‐Val (mAAPV) stimulates the expression of ECM proteins and inhibits the expression of metalloproteinases (MMPs) that degrade ECM proteins in Hs68 human fibroblast cells. In order to elucidate the underlying molecular mechanisms for the effects of mAAVP, we investigated the changes in gene expression in the presence of mAAPV using a cDNA microarray. Treatment with mAAPV resulted in decreased expression of MMP‐related genes such as MMP1, MMP3, TIMP1 and TIMP3 and increased expression of collagen genes, including COL1A1, COL1A2, COL3A1, COL5A1 and COL6A3. The pattern of gene expression regulated by mAAPV was very similar to that of gene expression induced by transforming growth factor (TGF)‐β, indicating that the TGF‐β signaling pathway is crucial for simultaneous activation of several ECM‐related genes by mAAPV. We examined whether the activation of SMAD, a downstream protein of TGF‐β receptor, is involved in the signal transduction pathway induced by mAAPV. The results demonstrate that mAAVP directly activates SMAD2 and induces SMAD3 to bind to DNA. In conclusion, our results demonstrate that mAAPV both enhances the expression of collagen and inhibits its degradation via production of protease inhibitors that prevent enzymatic breakdown of the ECM. The results suggest that mAAPV would be a useful ECM‐protecting agent. Copyright © 2014 John Wiley & Sons, Ltd.
Non‐natural Olefin Cyclopropanation Catalyzed by Diverse Cytochrome P450s and Other Hemoproteins
Authors: Heel Thomas , McIntosh John A. , Dodani Sheel C. , Meyerowitz Joseph T. , Arnold Frances H.
Published: October 2014

Recent work has shown that engineered variants of cytochrome P450BM3 (CYP102A1) efficiently catalyze non‐natural reactions, including carbene and nitrene transfer reactions. Given the broad substrate range of natural P450 enzymes, we set out to explore if this diversity could be leveraged to generate a broad panel of new catalysts for olefin cyclopropanation (i.e., carbene transfer). Here, we took a step towards this goal by characterizing the carbene transfer activities of four new wild‐type P450s that have different native substrates. All four were active and exhibited a range of product selectivities in the model reaction: cyclopropanation of styrene by using ethyl diazoacetate (EDA). Previous work on P450BM3 demonstrated that mutation of the axial coordinating cysteine, universally conserved among P450 enzymes, to a serine residue, increased activity for this non‐natural reaction. The equivalent mutation in the selected P450s was found to activate carbene transfer chemistry both in vitro and in vivo. Furthermore, serum albumins complexed with hemin were also found to be efficient in vitro cyclopropanation catalysts.
Development of a Halide‐Free Aluminium‐Based Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide
Authors: Castro‐Osma Jose A. , North Michael , Wu Xiao
Published: October 2014

Kinetic studies of the synthesis of glycerol carbonate from glycidol and carbon dioxide have been carried out. These showed that under suitable reaction conditions, bimetallic aluminium(salen) complex 4 is able to catalyse the conversion of epoxides into the corresponding cyclic carbonates without the need for a co‐catalyst.
Iridium‐Catalyst‐Based Autonomous Bubble‐Propelled Graphene Micromotors with Ultralow Catalyst Loading
Authors: Wang Hong , Sofer Zdeněk , Eng Alex Yong Sheng , Pumera Martin
Published: October 2014

A novel concept of an iridium‐based bubble‐propelled Janus‐particle‐type graphene micromotor with very high surface area and with very low catalyst loading is described. The low loading of Ir catalyst (0.54 at %) allows for fast motion of graphene microparticles with high surface area of 316.2 m2 g−1. The micromotor was prepared with a simple and scalable method by thermal exfoliation of iridium‐doped graphite oxide precursor composite in hydrogen atmosphere. Oxygen bubbles generated from the decomposition of hydrogen peroxide at the iridium catalytic sites provide robust propulsion thrust for the graphene micromotor. The high surface area and low iridium catalyst loading of the bubble‐propelled graphene motors offer great possibilities for dramatically enhanced cargo delivery.
Ordered Mesoporous ZSM‐5 Employing an Imidazolium‐Based Ionic Liquid
Authors: Sachse Alexander , Wuttke Caroline , Lissner Elízio , Oberson de Souza Michèle
Published: October 2014

Hierarchically porous ZSM‐5 was achieved by using a simple bottom‐up strategy combining zeolite seeds with imidazolium‐based ionic liquids. The bimodal ZSM‐5 with hexagonal arranged mesopores (3 nm) shows important activity in the acid catalysis of bulky compounds relative to conventional ZSM‐5.
Lithographische Druckplatten für Laserbelichtung
Authors: Baumann Harald
Published: October 2014

Lithographische Druckplatten für Laserbelichtung (CtP‐Platten) lassen sich in positiv‐ und negativ‐arbeitend unterteilen. Die Bilderzeugung der positiv‐arbeitenden Platten beruht auf der Spaltung von Wasserstoffbrückenbindungen zwischen Polymeren und IR‐Farbstoffen bei der NIR‐Belichtung, die zu erhöhter Entwicklerlöslichkeit führt. Negativ‐arbeitende Platten basieren entweder auf thermischer Koaleszenz von thermoplastischen Partikeln oder säure‐ und radikalinduzierter Vernetzung durch Belichtung. Der Artikel gibt einen Überblick über die chemischen Bestandteile und die Mechanismen der Bilderzeugung sowie einen Ausblick auf zukünftige Entwicklungen im Vergleich zu alternativen Technologien.
Die optischen Aufheller Fraxin und Aesculin
Authors: Drosky Philipp , Sander Madlen , Nakata Kazuhide , Siehl Hans‐Ullrich , Zeller Klaus‐Peter , Berger Stefan , Sicker Dieter
Published: October 2014

Die beiden strukturell verwandten Glycoside Fraxin und Aesculin wurden aus Eschenrindenextrakt mittels Gel‐Permeations‐Chromatographie über Sephadex LH‐20 rein isoliert. Diese anspruchsvolle Trennung ist ein Paradebeispiel für den präparativen Wert eines chemisch quervernetzten Dextran‐Gels. Mit Kieselgel 60 gelangt man nur zu reinem Aesculin. Die Begriffe Optische Aufheller und Fluoreszenz werden diskutiert. Alle analytischen Spektren sind vollständig entweder im Hauptteil oder in der supporting information unter www.chiuz.de wiedergegeben und werden eingehend interpretiert. Das Projekt stellt eine Fortsetzung des Buches “Classics in Spectroscopy” von S. Berger und D. Sicker (Wiley‐VCH 2009) dar.
Die pflanzliche Methan‐Bildung nachgeahmt
Authors: Feil Sylvia
Published: October 2014

Bei der natürlichen Bildung von Methan in abiotischen Prozessen – also ohne die Unterstützung von Enzymen – scheinen die Bedingungen klar: hohe Temperaturen und/oder Druck. Zwar ist bekannt, dass Pflanzen und Pilze Methan freisetzen, doch waren Reaktionswege und Vorstufen bislang unklar. Frank Keppler und seine Kollegen von der Universität Heidelberg präsentieren nun einen biomimetischen Weg von schwefelorganischen Verbindungen zu Methan unter milden, oxidativen Bedingungen [1].
Glukosamin verlängert Leben
Authors: Fischer‐Henningsen Doris
Published: October 2014

Glukosamin ist ein frei verkäufliches Nahrungsergänzungsmittel, das, wie kürzlich ein Forscherteam berichtete, die Lebenserwartung erhöht – zumindest bei Fadenwürmern und alternden Mäusen.
Effectiveness of Dichanthium annulatum in Watercourses for Reducing Sediment Delivery from Agricultural Watersheds
Authors: Krishna Rao Battu , Mishra Prasanta K. , Kurothe Ravi S. , Pande Vinod C. , Kumar Gopal
Published: October 2014

A field experiment was conducted to determine the efficacy of Dichantium annulatum grass filters in watercourses and to optimize the grass coverage in these watercourses. This experiment was conducted in 2% slope watercourses with varying filter grass coverage (0, 25, 50, 75, 100%) as main treatments and different flow rates (5, 10, 15, 20 L/s) as sub‐treatments. The inflow and outflow, flow velocity, depth of the flow, and sediment concentration was measured and analyzed for each run. The experimental results reveal that the grass filter strips are able to reduce the sediment concentration in the runoff water by six times (from 4.2 to 0.65 g/L). The filter strips are able to reduce the velocity of the runoff water by two times (from 1.06 to 0.47 m/s) and convert the supercritical flows into subcritical flows. The filter strips are able to increase the Manning's coefficient from 0.0323 to 0.1006 under various discharges. From the experiment, it can be concluded that more than 50% grass filter coverage in watercourses did not further reduce sediment concentration, outflow, flow velocity, and the Froude number and increase roughness of the channels. Based on these results, it is recommended that D. annulatum can be used as a filter in watercourses to prevent runoff and soil losses from crop fields and thereby reducing the sedimentation of downstream water bodies. The optimum grass coverage, i.e. 50% of the channel length, can maintain the maximum grass production with minimum soil loss.
Colour and spectral reflectance of stools from normal neonatal babies
Authors: Griffin Lewis D. , Sutcliffe Alastair G. , Bradbury Kimberley , Kumble Smitha , Mylonas Dimitris , Baker Alastair
Published: October 2014

Data is presented on the colour and spectral reflectances of stool samples from healthy young infants (mean age 6 days). The range of spectral reflectances is well described by a pigment mixture model with three components—a pale component corresponding to partially digested milk fats, a yellow component corresponding to bilirubin breakdown products, and a dark component corresponding to meconium and bilirubin. Most stools were tan, beige or olive but white, grey and light grey were also observed. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 585–591, 2015
An efficient graph data processing system for large‐scale social network service applications
Authors: Zhou Wei , Han Jizhong , Gao Yun , Xu Zhiyong
Published: October 2014

Trust in social network draws more and more attentions from both the academia and industry fields. Public opinion analysis is a direct way to increase the trust in social network. Because the public opinion analysis can be expressed naturally by the graph algorithm and graph data are the default data organization mechanism used in large‐scale social network service applications, more and more research works apply the graph processing system to deal with the public opinion analysis. As the data volume is growing rapidly, the distributed graph systems are introduced to process the large‐scale public opinion analysis. Most of graph algorithms introduce a large number of data iterations, so the synchronization requirements between successive iterations can severely jeopardize the effectiveness of parallel operations, which makes the data aggregation and analysis operations become slower. In this paper, we propose a large‐scale graph data processing system to address these issues, which includes a graph data processing model, Arbor. Arbor develops a new graph data organization format to represent the social relationship, and the format can not only save storage space but also accelerate graph data processing operations. Furthermore, Arbor substitutes time‐constrained synchronization operations with non‐time‐constrained control message transmissions to increase the degree of parallelism. Based on the system, we put forward two most frequently used graph applications on Arbor: shortest path and PageRank. In order to evaluate the system, we compare Arbor with the other graph processing systems using large‐scale experimental graph data, and the results show that it outperforms the state‐of‐the‐art systems. Copyright © 2014 John Wiley & Sons, Ltd.
Structural and Magnetic Properties of CoGen− (n=2–11) Clusters: Photoelectron Spectroscopy and Density Functional Calculations
Authors: Deng Xiao‐Jiao , Kong Xiang‐Yu , Xu Xi‐Ling , Xu Hong‐Guang , Zheng Wei‐Jun
Published: October 2014

A series of cobalt‐doped germanium clusters, CoGen−/0 (n=2–11), are investigated by using anion photoelectron spectroscopy combined with density functional theory calculations. For both anionic and neutral CoGen (n=2–11) clusters, the critical size of the transition from exo‐ to endohedral structures is n=9. Natural population analysis shows that there is electron transfer from the Gen framework to the Co atom at n=7–11 for both anionic and neutral CoGen clusters. The magnetic moments of the anionic and neutral CoGen clusters decrease to the lowest values at n=10 and 11. The transfer of electrons from the Gen framework to the Co atom and the minimization of the magnetic moments are related to the evolution of CoGen structures from exo‐ to endohedral.