bluuebunny/crossref_metadata_2025 huggingface dataset:
Manufacturing of AA2124 Aluminum Alloy Metal Matrix Composites Reinforced by Silicon Carbide Processed by Powder Metallurgy Techniques of High Energy Ball Milling and Hot Extrusion
Authors: de Araújo Filho Oscar Olimpio , de Araújo Everthon Rodrigues , de Lira Heronilton Mendes , Gonzalez Cezar Henrique , Silva Noelle D’emery Gomes , Urtiga Filho Severino Leopoldino
Published: July 2017

Aluminum alloy metal matrix composites are a class of materials object of large and intensive research during the last years. In this study an AA2124 aluminum alloy were processed by means of mechanical alloying added by 10, 20 and 20 percent of silicon carbide (SiC) in vibratory SPEX type mill during 60 and 120 minutes. After this the composites powders obtained were characterized by means of Scanning Electron Microscopy (SEM) plus Energy Dispersive Spectroscopy (EDS) to determine the powders morphology. In order to consolidate the AA2124 aluminum alloy composites reinforced by silicon carbide (SiC) composites, the powders processed by high energy ball milling technique were hot extruded and the billets were characterized by SEM to determine the microstructure and the distribution of the reinforced ceramic phase of silicon carbide throughout the aluminum matrix and at last the microhardiness Vickers technique were used to evaluate the mechanical properties.
Influence of the pH and Stirring Speed of the Electrodeposition Bath in the Performance of Zinc and Zinc-Nanocomposite Coatings
Authors: Marcolin Patrícia , Longhi Marielen , Zini Lucas Pandolphi , Proença Bianca , de Fraga Malfatti Célia , Battisti Lintha C. , Rieder Ester S. , Zattera Ademir José , Kunst Sandra Raquel , Oliveira Cláudia Trindade
Published: July 2017

With the increase of environmental restrictions, chromium and cadmium-based coatings have been replaced by zinc layers. These coatings can be obtained through electrodeposition, whose industrially established pH range is from 5.0 to 5.8, and stirring speed is uncontrolled, which has led to part rejections. In addition, the corrosion resistance of zinc coatings is inferior to cadmium and chromium coatings, which has boosted the research of zinc composite coatings. The proposed work presents the performance of zinc-bentonite composite coatings in regards to corrosion relating to pH variation and stirring speed. The samples were degreased for 5 minutes in a commercial degreasing solution at a temperature of 55 °C, with magnetic stirring and, posteriorly, submitted to a pickling process with a duration of 1 to 2 minutes in a commercial bath, followed by a washing process with deionized water. The electrolyte used for electrodeposition was a zinc bath with a chemical composition of 85 g/l ZnCl2, 210 g/l KCl and 25 g/l H3BO3. For the zinc-bentonite electrodepositions 20 g/l of bentonite nanoparticles was added to the bath. Zinc and zinc-bentonite coatings were characterized by scanning electron microscopy, open circuit potential and potentiodynamic polarization. This work shows that a 5.2 pH is the most recommended for the zinc electrodeposition process. Potentiodynamic polarization tests indicated that pure zinc coatings developed in the stirring speed of 380 rpm and zinc-bentonite produced in the stirring speed of 710 rpm showed the best results.
Development of the Self-Lubricating Steels by Compression of Granulated Powders
Authors: Demetrio V.B. , Bendo Tatiana , Binder Cristiano , Hammes Gisele , Orsi P.F. , de Mello José Daniel Biasoli , Klein Aloísio Neumo
Published: July 2017

Self-lubrication composites containing second phase particles incorporated into the volume of the material appears to be a promising solution for controlling friction and wear in modern systems. The objective of this work was the development of steels with low friction coefficient using granulated powders through a precursor (SiC), which generate carbon nodules in a ferrous matrix. The studied alloy composition was Fe+0,6C+3SiC using 2 wt.% of EVA as binder. In this study, the influence of the average size of the iron particles and silicon carbide (SiC) in the microstructure, mechanical and tribological properties was evaluated. The powders were first mixed in a "Y" type mixer, granulated drum, compressed and sintered in plasma in a single thermal cycle assuring binder extraction and sintering of components. The achieved results were close to those of alloys of the same composition produced via powder injection molding (PIM) but with processing time and cost close to those of conventional powder metallurgy (PM). Materials with yield strength of 250 MPa, durability of 2800 Nm and 0.11 friction coefficient were obtained.
Evaluation of Behavior of Aluminium-CNT Composite on the Equal-Channel Angular Extrusion
Authors: Teixeira Ariel , da Rocha Márcio Roberto , Arnt Angela Beatriz Coelho
Published: July 2017

Metal matrix composites (MMCs) are relatively new materials on science and materials engineering. In this work was used single-walled carbon nanotube (SWNT) as reinforcement in an aluminum matrix. For this purpose, 0.75% (by weight) of SWNT was dispersed with isopropanol using ultrasonication and mixed with particles of aluminum powder. The samples with and without SWNT were dried and compacted at room temperature with a pressure of 400 MPa for obtain a billet with 4,8x4,8x25,0 mm3. These compacted billet were subjected to Equal-Channel Angular Extrusion - ECAE (Φ=90 °) at room temperature. The influence of the presence of SWNT, of the number of extrusion passes (0, 1, and 3 passes), of the extrusion route (A or BC) and of the use of back pressure (0-65 MPa) in densification and hardness of the composite was evaluated. Optical microscopy was used to characterize the morphology of the aluminum grains, the dispersion of SWCNT and present pores in the samples. The results indicated that the density and hardness of the samples are increased with the increase in the number of extrusion passes and the use of back pressure. The microstructures showed alignment of the aluminum grains and of the CNT clusters in a direction close to the shear imposed by the ECAE process and increase of the dispersion because of the necking and defragmentation of the CNT clusters.
Rapid Solidification and Laser Cladding of Gas Atomized Ni-Nb-Sn Bulk Metallic Glass
Authors: Catto F.L. , Gabriel A.H.G. , Bolfarini C. , Kiminami Claudio Shyinti , Afonso Conrado Ramos Moreira
Published: July 2017

Glassy overspray powders of Ni59Nb35Sn6 (at%) bulk metallic glass (BMG) obtained by spray forming were used in order to produce coatings on AISI 1020 mild steel substrate by laser cladding of the pre-placed powders. Different laser parameters, resulting in a variation of the power density, PD (J/mm2), were tested with a Yb fiber laser (up to 500 W). Gas atomized powders, suction cast sample trough copper mold casting and the laser clad tracks were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and coatings were subjected to measurements of Vickers microhardness. Atomized powder obtained showed no crystalline phases formation up to 425 μm, indicating good glass forming ability (GFA) of Ni59Nb35Sn6 (at%) alloy. Microstructure characterization confirmed maximum glassy dimension of tc =1mm for the Ni59Nb35Sn6 (at%). Laser cladding track showed nanocrystalline phases embedded in a glassy matrix with Vickers microhardness ranging from 336 to 1184 HV.
Supercapacitor Application of Powder Prepared Using the Hydrogenation Disproportionation Desorption and Recombination (HDDR) Process in Graphene Oxide
Authors: Casini Julio César Serafim , Fernandez Antonio Paulo Rodrigues , de Oliveira Rene Ramos , Sakata S. K. , Faria R.N.
Published: July 2017

Graphene (G) has been attracted great interest for its excellent electrical properties. However, the large-scale production of graphene is presently unfeasible. Graphene oxide (GO) can be (partly) reduced to graphene-like sheets by removing the oxygen-containing groups with the recovery of a conjugated structure. It can be produced using inexpensive graphite as raw material by cost-effective chemical methods. Although hydrogen (mixed with argon) at high temperature (1100°C) has been employed to reduce GO powder, the hydrogenation disproportionation desorption and recombination (HDDR) process in particular was unreported for this purpose. In the present work, attempts of reducing GO powder using the HDDR process have been carried out and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The experimental results of processing graphene oxide powder using unmixed hydrogen at moderate temperatures (about 850°C) and relatively low pressures (<2 bars) have been reported.
Erucamide-Nanoclay Systems Obtained by Intercalation Process
Authors: Silvano Josiane R. , Mello J.M.M. , Silva Lucinao Luiz , Riella Humberto Gracher , Fiori Márcio Antônio
Published: July 2017

A major challenge in the manufacture of films for polymeric packaging is the definition and setting of the friction coefficient (FCO) for the film surfaces. The FCO values are established with the incorporation of additives during the processing of the polymeric films. But, the homogenization of these additives in the polymeric matrix is very difficult. The additives have different polarity that the matrix polymeric and not are mixable. So, these additives migrate for the surface of the polymeric films easily. Several molecules are used as sliding additives, but among the most efficient are the amides molecules, highlighting the erucamide. This molecule promotes the decrease of the FOC but due its quick migration for the polymeric film surface provides numerous problems for the manufacture of the polymeric packaging and during its application as the product. In this work a nanocomposite (MMT-ERU) was obtained by an intercalation process to improve the compatibility between the polymeric materials and the erucamide molecules. The results shown in this work refers to the studies about the intercalation processes of the erucamide molecules into nanoclays (montmorillonite) to obtain the nanocomposite MMT-ERU. The effect of the temperature and the percentage of the nanoclay in the intercalation processes were studied. The results of x-ray diffraction and differential scanning calorimetry shown that erucamide molecules were intercalated in the nanoclay structures and that intercalation efficiency depends positively of the temperature and percentage amount of the nanoclay in the reaction medium.
Analysis of the Microwave Heating Effect in the Comminution Efficiency of Iron Ore Particles
Authors: da Silval Leonardo Martins , Nascimento M. , Mota I.O. , Oliveira E.M. , Castro J.A.
Published: July 2017

Heating iron ore fine particles using microwave energy has been effective due to the different interactions between minerals and gangue in the magnetic field generated by the microwave. In this way, this paper proposes to use microwave energy to heat the particles of iron ore to promote micro cracks and fissures, which would facilitate the comminution and pulverization process to produce pellet feed. It was analyzed different conditions of heating and cooling in the comminution step. By using techniques of scanning electron microscopy (SEM) and image analysis it was possible to assess and quantify the micro cracks and subsequent analysis of the energy and size fragmentation in the comminution step of ultrafine particles.
The Influence of the Sintering Temperature on the Grain Growth of Tungsten Carbide in the Composite WC-8Ni
Authors: Miranda Fabio , Rodrigues Daniel , Nakamato F.Y. , Frajuca C. , Santos G.A.
Published: July 2017

This study aims to highlight the grains growth of tungsten carbide in the nickel binder phase, in function of sintering temperature of a hot isostatic pressed - HIP (at 60 bar) material, targeting the morphological behavior of the grain size and densification of the composite WC-8Ni. Cylindrical samples 25 mm x 15 mm were sintered in compression at temperatures ranging from 1380 °C to 1460 °C. The results showed that increasing the sintering temperature, there is an increase in WC grain size, the hardness decreases and the porosity is reduced increasing the specific gravity.
Hot Tensile Behavior and Fracture Characteristics of a Plasma Nitrided Maraging 300 Steel
Authors: Reis Adriano Gonçalves , Reis Danieli Aparecida Pereira , Abdalla Antônio Jorge , Otubo Jorge , Couto Antônio Augusto , Neto Francisco Piorino
Published: July 2017

The influence of plasma nitriding of a maraging 300 steel on mechanical properties at high temperature has been studied. Samples were tensile tested at 600°C in four conditions: solution treated (MAR-S), solution treated and aged (MAR-SA), solution treated and plasma nitrited (MAR-SP) and solution treated, aged and plasma nitrited (MAR-SAP). In the same sequence, the yield strength and ultimate tensile strength increased slightly respectively from 1073 to 1189 MPa and 1174 to 1301 MPa, an increase of about 10% due to plasma nitriding. All the samples presented similar values of elongation, around 18%, but the cross section area reduction decreased significantly by plasma nitriding from ~70% for MAR-S and MAR-SA to ~45% for MAR-SP and MAR-SAP, that is an decrease of 36% in average. This decrease is attributed to brittle fracture nucleated at 50 μm thick iron nitride layer. The inner fracture surface of the tensile tested specimens was predominantly ductile presenting characteristic microcavities.
B-H Loop of Sintered Stainless Steel 410 Adjusted by Superellipse Model
Authors: Sampaio da Silva Fernanda A. , Rodrigues Daniel , Concílio Gilberto Vicente , de Castro Jose Adilson , de Campos Marcos Flavio
Published: July 2017

B-H loop obtained from frequencies higher than 40 Hz can be satisfactorily adjusted by Superellipse model. Examples of application of the Superellipse model for sintered stainless steel 410 are presented. The parameters of model (four parameters) may have assigned physical meanings that reveal magnetic behavior, such as coercivity and remanence. Furthermore, they are directly related to the aesthetics of the B-H loop. The Superellipse model is very versatile, describing the most closed shapes (rods) and the more open (rectangular). The obtained parameter values reflect the magnetic variability of sample. In addition, by applying the model it was possible to analyze the magnetic and structural properties of a sintered stainless steel sample.
Thermal Aging of NdFeB Compression Molded Magnets
Authors: Rodrigues Daniel , Concílio Gilberto Vicente , de Castro Jose Adilson , de Campos Marcos Flavio
Published: July 2017

Compression moulded rare earth magnets are used in many applications, and one of them is in electrical motors, which can operate at temperatures as high as 150 °C. In high temperatures, oxidation and phase transformations may affect magnetic properties. Another issue to be considered is polymer degradation. In this paper cylindrical samples of a commercial ready-to-press raw material (MQPB+, Molycorp-Magnequench) were pressed to densities close to 5.50 g/cm3. These samples were cured (low temperature heat treatment) and thermal aged at 200 °C for 72 hours, under dynamic air. Physical characteristics (weight, dimensions and densities) and magnetic properties were measured at room temperature in a TCH2020 hysteresigraph (Globalmag). Degradation of magnetic properties was observed, and oxidation seems to be the main reason.
Effects of wind-induced sediment resuspension on distribution and morphological traits of aquatic weeds in shallow lakes
Authors: Bertrin Vincent , Boutry Sébastien , Jan Gwilherm , Ducasse Greta , Grigoletto Florent , Ribaudo Cristina
Published: July 2017

The spread of invasive aquatic plants (i.e., aquatic weeds) requires a broader knowledge of the factors determining their settlement at the lake scale, in order to improve management practices and biomonitoring. Among hydrodynamic pressures, wave action might influence submerged vegetation distribution in shallow lakes and potentially engender modifications of plant morphological traits. We here report a field survey conducted between 2014 and 2015 in French Atlantic Lakes to assess the spatial distribution and biomass production of two rooted aquatic weeds, Egeria densa Planch. and Lagarosiphon major (Ridl.) Moss, in relation to wind-induced sediment resuspension, water depth and sedimentary features. Moreover, we explored the relation between plant morphological traits and hydrodynamic disturbance under in situ conditions. At the lake scale, E. densa and L. major formed extensive monospecific stands, and occurred in the same areas only at low biomass. Both monospecific and mixed stands preferentially developed in shallow-sheltered or deep-exposed areas. Plant morphological traits showed different patterns in function of sediment resuspension according to the species and the lake. The influence of resuspension was however not systematic, with many cases where morphological traits were not affected at all. Maximum stem length appeared to be the most correlated trait towards sediment resuspension. Moreover, we found a significant correlation between the biomass and the sedimentary organic matter, indicating an interaction between the organic substrate preference of the plants and the effect of the canopy on fine particles sedimentation. On the whole, we highlighted the link between plant distribution, phenotypic plasticity and sediment resuspension, with calm-water zones favouring the settlement of dense vegetated stands. Our study could thus contribute to improve prediction models for identifying suitable areas for potential colonization by aquatic weeds. Further research is needed to better understand the role played by hydraulic forces in structuring the habitats in shallow lakes.
Host molecular factors and viral genotypes in the mother-to-child HIV-1 transmission in sub-Saharan Africa
Authors: M. Mouafo Linda Chapdeleine , Dambaya Béatrice , Ngoufack Nicole N. , Nkenfou Céline N.
Published: July 2017

Maternal viral load and immune status, timing and route of delivery, viral subtype, and host genetics are known to influence the transmission, acquisition and disease progression of human immunodeficiency virus-1 (HIV-1) infection. This review summarizes the findings from published works on host molecular factors and virus genotypes affecting mother to child transmission (MTCT) in Africa and identifies the gaps that need to be addressed in future research. Articles in PubMed, Google and AIDSearch and relevant conference abstracts publications were searched. Accessible articles on host factors and viral genetics impacting the MTCT of HIV, done on African populations till 2015 were downloaded. Forty-six articles were found and accessed; 70% described host genes impacting the transmission. The most studied gene was the CCR5 promoter, followed by the CCR2-64I found to reduce MTCT; then SDF1-3’A shown to have no effect on MTCT and others like the DC-SIGNR, CD4, CCL3 and IP- 10. The HLA class I was most studied and was generally linked to the protective effect on MTCT. Breast milk constituents were associated to protection against MTCT. However, existing studies in Sub Saharan Africa were done just in few countries and some done without control groups. Contradictory results obtained may be due to different genetic background, type of controls, different socio-cultural and economic environment and population size. More studies are thus needed to better understand the mechanism of transmission or prevention.
Concurrent T790M and L858R mutations in treatment-naïve metastatic non-small-cell lung cancer: A therapeutic challenge – Current treatment strategies and promising therapies of the future in a nutshell
Authors: Babu M. C. Suresh , Babu K. Govind , Lokesh K. N. , Rajeev L. K. , Bhat Gita R.
Published: July 2017

De novo (pretreatment) epidermal growth factor receptor T790M mutation in non-small-cell lung cancer (NSCLC) is rare when detected by standard genotyping methods. We present a case of concurrent de novo T790M and L858R mutations detected by direct sequencing in treatment-naïve metastatic NSCLC. This case is worthy of mention as the presence of this mutation has a bearing on the choice of treatment. This article aims to evaluate the clinical outcome for metastatic NSCLC with de novo T790M mutation and formulate an optimum treatment plan in this clinical scenario. The novel targeted therapy agents have also been reviewed.
Extranodal natural killer/T cell lymphoma with cardiac and abdominopelvic nodular deposits: Unique presentation on 18-fluorodeoxyglucose positron emission tomography computed tomography scan
Authors: Mahajan Shimpi , Maitra Sudeshna , Singh Natasha , Pereira Melvika
Published: July 2017

Cardiac lymphoma as secondary extension of non-Hodgkin's lymphoma is described in 30% of autopsies; however, a few cases are diagnosed in vivo. Primary lymphoma of the heart and pericardium is rare, accounting for 1.3% of primary cardiac tumors and only 0.5% of extranodal lymphomas at autopsy. We present a unique case of 68-year-old man diagnosed with extranodal lymphoma with cardiac and abdominopelvic nodular deposits on 18-fluorodeoxyglucose positron emission tomography-computed tomography scan findings.
Матричные модели и размерности в вершинах гиперкубов
Authors: Morozov Aleksei Yur'evich , Morozov Andrei Alekseevich , Popolitov Aleksandr Viktorovich
Published: July 2017

Рассматриваются корреляционные функции в теории Черна-Саймонса (полиномы узлов). Используется подход, в котором каждая диаграмма узла ассоциируется с гиперкубом. При этом основную роль играет число циклов, на которые диаграмма разбивается при различных разрешениях. Некоторые функции от этих чисел далее можно интерпретировать как размерности градуированных пространств, связанных с вершинами гиперкубов, но поиск этих функций является весьма нетривиальной задачей. Ранее было высказано предложение решать эту проблему с помощью методов теории матричных моделей по аналогии с топологической рекурсией. Предлагается развитие этой идеи и приводится широкий набор нетривиальных примеров, связанных как с обычными, так и с виртуальными узлами и зацеплениями. Наиболее мощная версия формализма свободно связывает обычные узлы/зацепления с виртуальными; более того, она позволяет продвинуться за пределы связанного с узлами множества $(2,2)$-валентных графов.
Family and individual predictors and mediators of adolescent physical activity
Authors: Tabak Izabela , Mazur Joanna , Nałęcz Hanna
Published: July 2017

Background

In recent years, many reviews of research have demonstrated that the correlations between the physical activity of children and their parents are not as obvious as was once believed. Family factors constitute determinants of children’s physical activity; however, this influence can be mediated by other factors. The aim of the analyses was to examine the mechanisms of the relationships between parental and individual factors: to examine whether parental modelling of physical activity and parental support are direct and indirect predictors of children’s physical activity and whether self-efficacy is a mediator of these relationships.

Participants and procedure

Data from 1,287 Polish adolescents aged 14 to 18 were analysed. The study used questions and scales regarding perceived parental modelling of physical activity (perceived parental physical activity and joint activities), received parental support, and self-efficacy, moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) of adolescents. Statistical analyses included partial correlations, regression analyses and structural equation modelling.

Results

It was found that self-efficacy, support, gender and parental modelling are independent predictors of physical activity in adolescents; the strongest predictors are self-efficacy and support. Support was a mediator of the relationship between modelling and physical activity and between modelling and self-efficacy. Self-efficacy was a mediator of the relationship between support and physical activity.

Conclusions

Parental physical activity, as well as parents’ engagement in joint activity and children’s activity, strengthens self-efficacy in adolescents and predisposes young people to maintain physically active behaviour.
Mesospheric Temperatures over Apache Point Observatory (32°N, 105°W) Derived from
Sloan Digital Sky Survey Spectra
Authors: Kim Gawon , Kim Yong Ha , Lee Young Sun
Published: July 2017

We retrieved rotational temperatures from emission lines of the OH airglow (8-3)
band in the sky spectra of the Sloan digital sky survey (SDSS) for the period 2000-2014,
as part of the astronomical observation project conducted at the Apache Point
observatory (32°N, 105°W). The SDSS temperatures show a typical seasonal variation of
mesospheric temperature: low in summer and high in winter. We find that the temperatures
respond to solar activity by as much as 1.2 K ±0.8 K per 100 solar flux units, which is
consistent with other studies in mid-latitude regions. After the seasonal variation and
solar response were subtracted, the SDSS temperature is fairly constant over the 15 year
period, unlike cooling trends suggested by some studies. This temperature analysis using
SDSS spectra is a unique contribution to the global monitoring of climate change because
the SDSS project was established for astronomical purposes and is independent from
climate studies. The SDSS temperatures are also compared with mesospheric temperatures
measured by the microwave limb sounder (MLS) instrument on board the Aura satellite and
the differences are discussed.
Mission Orbit Design of CubeSat Impactor Measuring Lunar Local Magnetic
Field
Authors: Lee Jeong-Ah , Park Sang-Young , Kim Youngkwang , Bae Jonghee , Lee Donghun , Ju Gwanghyeok
Published: July 2017

The current study designs the mission orbit of the lunar CubeSat spacecraft to
measure the lunar local magnetic anomaly. To perform this mission, the CubeSat will
impact the lunar surface over the Reiner Gamma swirl on the Moon. Orbit analyses are
conducted comprising ΔV and error propagation analysis for the CubeSat mission orbit.
First, three possible orbit scenarios are presented in terms of the CubeSat’s impacting
trajectories. For each scenario, it is important to achieve mission objectives with a
minimum ΔV since the CubeSat is limited in size and cost. Therefore, the ΔV needed for
the CubeSat to maneuver from the initial orbit toward the impacting trajectory is
analyzed for each orbit scenario. In addition, error propagation analysis is performed
for each scenario to evaluate how initial errors, such as position error, velocity
error, and maneuver error, that occur when the CubeSat is separated from the lunar
orbiter, eventually affect the final impact position. As a result, the current study
adopts a CubeSat release from the circular orbit at 100 km altitude and an impact slope
of 15°, among the possible impacting scenarios. For this scenario, the required ΔV is
calculated as the result of the ΔV analysis. It can be used to practically make an
estimate of this specific mission’s fuel budget. In addition, the current study suggests
error constraints for ΔV for the mission.
Chemical Composition of RR Lyn – an Eclipsing Binary System with Am and λ Boo Type
Components
Authors: Jeong Yeuncheol , Yushchenko Alexander V. , Doikov Dmytry N. , Gopka Vira F. , Yushchenko Volodymyr O.
Published: July 2017

High-resolution spectroscopic observations of the eclipsing binary system RR Lyn
were made using the 1.8 m telescope at the Bohuynsan Optical Astronomical Observatory in
Korea. The spectral resolving power was R = 82,000, with a signal to noise ratio of S/N
> 150. We found the effective temperatures and surface gravities of the primary and
secondary components to be equal to Teff = 7,920 & 7,210 K and log(g) = 3.80 &
4.16, respectively. The abundances of 34 and 17 different chemical elements were found
in the atmospheric components. Correlations between the derived abundances with
condensation temperatures and the second ionization potentials of these elements are
discussed. The primary component is a typical metallic line star with the abundances of
light and iron group elements close to solar values, while elements with atomic numbers
Z > 30 are overabundant by 0.5–1.5 dex with respect to solar values. The secondary
component is a λ Boo type star. In this type of stars, CNO abundances are close to solar
values, while the abundance pattern shows a negative correlation with condensation
temperatures.
Quantification of CO emissions from the city of Madrid using MOPITT satellite retrievals and WRF simulations
Authors: Dekker Iris , Houweling Sander , Aben Ilse , Röckmann Thomas , Krol Maarten , Martínez-Alonso Sara , Deeter Merritt , Worden Helen
Published: July 2017

Abstract. The growth of mega-cities leads to air quality problems directly affecting the citizens. Satellite measurements are becoming of higher quality and quantity, which leads to more accurate satellite retrievals of the enhanced air pollutant concentrations over large cities. In this paper, we compare and discuss both an existing and a new method for estimating urban scale trends in CO emissions using multi-year retrievals from the MOPITT satellite instrument. The first method is mainly based on satellite data, which has the advantage of fewer assumptions, but also comes with uncertainties and limitations as shown in this paper. To improve the reliability of urban to regional scale emission trend estimation, we simulate MOPITT retrievals using the Weather Research and Forecast model with chemistry core (WRF-Chem). The difference between model and retrieval is used to optimize CO emissions in WRF-Chem, focusing on the city of Madrid, Spain. This method has the advantage over the existing method in that it allows both a trend analysis of CO concentrations and a quantification of CO emissions. Our analysis confirms thatMOPITT is capable of detecting CO enhancements overMadrid, although significant differences remain between the yearly averaged model output and satellite measurements (R2 = 0.75) over the city. After optimization, we find Madrid CO emissions to be lower by 48 % for 2002 and by 17 % for 2006 compared with the EdgarV4.2 emission inventory. The MOPITT derived emission adjustments lead to better agreement with the European emission inventory TNO-MAC-III for both years. This suggests that the downward trend in CO emissions over Madrid is overestimated in EdgarV4.2 and more realistically represented in TNO-MAC-III. However, our satellite and model based emission estimates have large uncertainties, around 20 % for 2002 and 50 % for 2006.
Nanoparticle Growth by Particle Phase Chemistry
Authors: Apsokardu Michael J. , Johnston Murray V.
Published: July 2017

Abstract. The ability of particle phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2–100 nm diameter range is investigated through the use of a growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particle larger than about 20 nm in diameter. The growth rate enhancement increases linearly with increasing particle diameter and is dependent on the gas phase mixing ratio of the semi-volatile reactant and the reaction rate constant. The results are discussed in the context of recent experimental measurements of particle size-dependent molecular composition and the relationship between accretion product formation and cloud condensation nuclei (CCN) activity.
Delayed Recovery of mid-latitude lower stratospheric Halogen Loading
Authors: Engel Andreas , Bönisch Harald , Ostermöller Jennifer
Published: July 2017

Abstract. Chlorine and bromine atoms can lead to catalytic destruction of ozone in the stratosphere. Therefore the use and production of ozone depleting substances (ODS) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent Effective Stratospheric Chlorine (EESC) has been adapted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a new formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. The improved formulation shows that EESC levels in the year 1980 for the mid latitude lower stratosphere were significantly lower than previously calculated. 1980 marks the year commonly defined as the onset of anthropogenic ozone depletion in the stratosphere. Assuming that the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than currently assumed in this region of the stratosphere. Based on the improved formulation, EESC level at mid-latitudes will reach this landmark only in 2060. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We conclude that, under the assumptions that all other atmospheric parameters like stratospheric dynamics and chemistry are unchanged, the recovery of mid latitude stratospheric ozone would be expected to be delayed by about a 10 years, in a similar way as EESC.
Ozone sensitivity to varying greenhouse gases and ozone-depleting substances in CCMI simulations
Authors: Morgenstern Olaf , Akiyoshi Hideharu , Yamashita Yousuke , Kinnison Douglas E. , Garcia Rolando R. , Plummer David A. , Scinocca John , Zeng Guang , Rozanov Eugene , Stenke Andrea , Revell Laura E. , Pitari Giovanni , Mancini Eva , Di Genova Glauco , Dhomse Sandip S. , Chipperfield Martyn P.
Published: July 2017

Abstract. Ozone fields simulated for the Chemistry-Climate Model Initiative (CCMI) will be used as forcing data in the 6th Coupled Model Intercomparison Project (CMIP6). Here we assess, using reference and sensitivity simulations produced for phase 1 of CCMI, the suitability of CCMI-1 model results for this process, investigating the degree of consistency amongst models regarding their responses to variations in individual forcings. We consider the influences of methane, nitrous oxide, a combination of chlorinated or brominated ozone-depleting substances (ODSs), and a combination of carbon dioxide and other greenhouse gases (GHGs). We find varying degrees of consistency in the models' responses in ozone to these individual forcings, including some considerable disagreement. In particular, the response of total-column ozone to these forcings is less consistent across the multi-model ensemble than profile comparisons. The likely cause of this is lower-stratospheric transport and dynamical responses exhibiting substantial inter-model differences. The findings imply that the ozone fields derived from CCMI-1 are subject to considerable uncertainties regarding the impacts of these anthropogenic forcings.
Multiphase Reaction of SO2 with NO2 on CaCO3 Particles. 1. Oxidation of SO2 by NO2
Authors: Zhao Defeng , Song Xiaojuan , Zhu Tong , Zhang Zefeng , Liu Yingjun
Published: July 2017

Abstract. Heterogeneous/multiphase reaction of SO2 with NO2 on solid or aqueous particles is thought to be a potentially important source of sulfate in the atmosphere, for example, during heavily polluted episodes (haze), but the reaction mechanism and rate are uncertain. In this study, we investigated the heterogeneous/multiphase reaction of SO2 with NO2 on individual CaCO3 particles in N2 using Micro-Raman spectroscopy in order to assess the importance of the direct oxidation of SO2 by NO2. In the SO2/NO2/H2O/N2 gas mixture, the CaCO3 solid particle was first converted to the Ca(NO3)2 droplet by the reaction with NO2 and the deliquescence of Ca(NO3)2, and then NO2 oxidized SO2 in the Ca(NO3)2 droplet forming CaSO4, which appeared as needle-shaped crystals. Sulfate was mainly formed after the complete conversion of CaCO3 to Ca(NO3)2, that is, during the multiphase oxidation of SO2 by NO2. The precipitation of CaSO4 from the droplet solution promoted sulfate formation. The reactive uptake coefficient of SO2 for sulfate formation is on the order of 10−8, and RH enhanced the uptake coefficient. We estimate that the direct multiphase oxidation of SO2 by NO2 is not an important source of sulfate in the ambient atmosphere compared with the SO2 oxidation by OH in the gas phase.
Spatial and temporal variability in coccolithophore abundance and
distribution in the NW Iberian coastal upwelling system
Authors: Ausín Blanca , Zúñiga Diana , Flores Jose Abel , Cavaleiro Catarina , Froján María , Villacieros-Robineau Nicolás , Alonso Pérez Fernando , Arbones Belén , Santos Celia , de la Granda Franciso , Castro Carmen G. , Abrantes Fátima , Eglinton Timothy I. , Salgueiro Emilia
Published: July 2017

Abstract. For the first time a systematic investigation of the coccolithophore ecology based on the spatial and temporal variability in their abundance and distribution through the water column was performed for the NW Iberian coastal upwelling system. From July 2011 to June 2012 monthly sampling at different water depths was conducted at two stations located along the 42º N parallel. Total coccolithophore abundances were higher at the offshore station where warmer and nutrient–depleted waters favoured coccolithophore rather than diatom blooming, the other phytoplankton group that is known to be dominant at the onshore location. In seasonal terms, coccolithophore blooms were registered at both stations during upwelling seasons, coinciding with high irradiance levels and generally in conjunction with stratified and nutrient–poor conditions in the water column, but also when colder and nutrient–rich subsurface waters upwelled onto the continental shelf. On the contrary, despite minimum abundances were generally found during downwelling periods, unexpectedly high coccolithophore abundances were registered in subsurface waters at the onshore station. This finding was only explained if strong storms during downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of the autochthonous coccolithophore community structure. Major composition of coccolithophore assemblages at both locations was dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, and Syracosphaera spp. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccolithophore abundance. Our findings will provide relevant information in regards to the use of fossil coccolithophore assemblages in marine sediment records to infer environmental conditions in the past, which is of particular relevance in Paleoceanography. E. huxleyi and the small Gephyrocapsa group are proposed as proxies for the upwelling regime and high primary production. Conversely, F. profunda is suggested as a proxy for the downwelling regime and low productivity conditions. Finally, the assemblage composed by Syracosphaera pulchra, Coronosphaera mediterranea, and Rhabdosphaera clavigera may be used as a useful indicator of the presence of warm and nutrient–poor southerly waters conveyed by the Iberian Poleward Current.
A global water resources ensemble of hydrological models: the eartH2Observe Tier-1 dataset
Authors: Schellekens Jaap , Dutra Emanuel , Martínez-de la Torre Alberto , Balsamo Gianpaolo , van Dijk Albert , Sperna Weiland Frederiek , Minvielle Marie , Calvet Jean-Christophe , Decharme Bertrand , Eisner Stephanie , Fink Gabriel , Flörke Martina , Peßenteiner Stefanie , van Beek Rens , Polcher Jan , Beck Hylke , Orth René , Calton Ben , Burke Sophia , Dorigo Wouter , Weedon Graham P.
Published: July 2017

Abstract. The dataset presented here consists of an ensemble of 10 global hydrological and land surface models for the period 1979–2012 using a reanalysis-based meteorological forcing dataset (0.5° resolution). The current dataset serves as a state of the art in current global hydrological modelling and as a benchmark for further improvements in the coming years. A signal-to-noise ratio analysis revealed low inter-model agreement over (i) snow-dominated regions and (ii) tropical rainforest and monsoon areas. The large uncertainty of precipitation in the tropics is not reflected in the ensemble runoff. Verification of the results against benchmark datasets for evapotranspiration, snow cover, snow water equivalent, soil moisture anomaly and total water storage anomaly using the tools from The International Land Model Benchmarking Project (ILAMB) showed overall useful model performance, while the ensemble mean generally outperformed the single model estimates. The results also show that there is currently no single best model for all variables and that model performance is spatially variable. In our unconstrained model runs the ensemble mean of total runoff into the ocean was 46 268 km3 yr−1 (334 kg m−2 yr−1), while the ensemble mean of total evaporation was 537 kg m−2 yr−1. All data are made available openly through a Water Cycle Integrator portal (WCI, wci.earth2observe.eu), and via a direct http and ftp download. The portal follows the protocols of the open geospatial consortium such as OPeNDAP, WCS and WMS. The DOI for the data is https://doi.org/10.1016/10.5281/zenodo.167070.
A remote-control datalogger for large-scale resistivity surveys and robust processing of its signals using a software Lock-In approach
Authors: Oppermann Frank , Günther Thomas
Published: July 2017

Abstract. We present a new versatile datalogger that can be used for a wide range of possible applications in geosciences. It is adjustable in signal strength and sampling frequency, battery-saving and can remotely be controlled over Global System for Mobile Communication (GSM) connection so that it saves running costs, particulaly in monitoring experiments. Internet connection allows for checking functionality, controlling schedules and optimizing preamplification. We mainly use it for large-scale Electrical Resistivity Tomography (ERT), where it independently registers voltage time series on three channels while a square wave current is injected. For the analysis of this time series we present a new approach that is based on the Lock-In (LI) method, mainly known from electronic circuits. The method searches the working point (phase) using three different functions based on a mask signal, and determines the amplitude using a direct current (DC) correlation function. We use synthetic data with different types of noise to compare the new method with existing approaches, i.e. selective stacking and a modified Fast Fourier Transformation (FFT) based approach that assumes a 1/f noise characteristics. All methods give comparable results, the LI being better than the well established stacking method. The FFT approach can be even better but only if the noise strictly follows the assumed characteristics. If overshoots are present in the data, which is typical in the field, FFT performs worse even with good data which is why we conclude that the new LI approach is the most robust solution. This is also proved by a field data set from a long 2D ERT profile.
Multi-level qualification of Parafluvial Exchange within the Hyporheic Zone Affected by River Sinuosity and Seasonal Change using Multi-tracer Methods
Authors: Meghdadi Amin reza , Eyvazi Morteza
Published: July 2017

Abstract. Exchange of water in the parafluvial zone, located along the boundaries of meandering streams, arises in response to seasonal variation and spatial distribution. Remarkably, few studies have applied multi-tracer methods for qualitative scrutiny of losing (recharge) or gaining (discharge) reaches along the parafluvial zone. Hence, the main objective of this study is to qualitatively characterize the spatio-temporal alteration in parafluvial exchange within the hyporheic zone (PEHZ) by simultaneous application of multi-tracer methods. For this approach, first, Hierarchical Cluster Analysis (HCA) in conjunction with groundwater hydrochemistry analysis was used to evaluate the representativeness of parafluvial assessment network. Then, water stable isotope compositions (δ18O and δ2H), radioisotope (222Rn), and environmental tracers (Temperature and EC) were measured at multiple depths (20 cm to 100 cm depths below streambed) during the wet and dry season to qualitatively elucidate the PEHZ in the Ghezel-Ozan River, a third order river located in the northwest of Iran. By groundwater hydrochemistry assessment identified, NaHCO3 and CaHCO3 as the dominant water type in dry and wet season, respectively. Moreover, the HCA approach designed two different clusters for each season for accurate interpretation of PEHZ. Results obtained from stable isotope and environmental tracer analysis of bore water, surface water, and parafluvial water distinguished stream-aquifer connectivity with highly seasonal and spatial variations. In the dry season, for example, δ18O, δ2H, and EC varied from −3.59 to −1.88 (‰ VSMOW), −31.08 to −24.06 (‰ VSMOW), and 234 to 740.65  μS/cm respectively. Also, the results acquired from the integration of δ18O and EC revealed complex spatio-temporal stream-aquifer connectivity (PEHZ). In low flow conditions, groundwater outflow mainly occurred at 100 cm depth while the dominance of groundwater outflow at 20 cm depth prevailed during high flow conditions. The continuous and point scale measurements of temperature and 222Rn were highly in accordance with the results of δ18O and EC. Furthermore, diel temperature fluctuation, as well as radon activity variations at multi-level scale, expressed the PEHZ (especially at depth greater than 60 cm) are affected by large-scale regional flow-field which is embedded within. The synthesized approaches used in this study provide a useful insight into the spatiotemporal changes of stream-aquifer connectivity which make the more efficient monitoring and interpretation of hydrological processes possible. They can be, furthermore, utilized to pinpoint the losing/gaining reaches accurately to tackle environmental problems such as monitoring the transport of anthropogenic contaminants in a system.