bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractAerosol‐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

AbstractAn 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

AbstractThe 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

AbstractThe 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

AbstractTerrestrial 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

AbstractModels 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

AbstractFluid 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.
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

AbstractHeterogeneous 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

ABSTRACTThermo‐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

ABSTRACTSodium 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

AbstractWe 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.
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

AbstractRecent 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

AbstractKinetic 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

AbstractA 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

AbstractHierarchically 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

AbstractLithographische 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

AbstractDie 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

AbstractBei 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].