bluuebunny/crossref_metadata_2025 huggingface dataset:
Tribological Properties of Basalt Fibers - A Review
Authors: Ullegaddi Kalmeshwar , Mahesha C.R. , Shivarudraiah Shivarudraiah
Published: August 2019

Now a days natural fibers are progressively projected as a choice of conventional synthetic fibers which causes an adverse impact on the surroundings. Rise within the utilization of environment-friendly natural fibers as reinforcement for the manufacture of lightweight, low-cost polymer with excellent mechanical, thermal and tribological properties can be made globally. One such material of interesting material being presently used is basalt fiber, which is the most-efficient and provides important properties over Carbon fibers, Glass fiber, and some other fibers. In this attempt, an effort made to showcase the tribological properties achieved for application in specific wear conditions like abrasive, sliding and erosion of basalt fiber reinforced polymer composites.
Analysis of the Tribological Properties of Commercial Pure (CP) Aluminum Developed by Chip Consolidation through Equal Channel Angular Pressing (ECAP)
Authors: Vittel Rao Rajendara Rao Krishnaji Rao , Gudimetla Kondaiah , Kumar Mariappan Senthil , Kumar S. Ramesh , Venkatachalam Perumal
Published: August 2019

The goal of this research work is to study the role of equal channel angular pressing on consolidation behavior of machined chips of CP Al through ECAP. The chips are collected by orthogonal cutting with cutting edge angle 75° and depth of cut 0.2 mm. The ECAP die with Φ = 90° (channel angle) and Ψ = 20° (corner angle) is used for consolidation of machined chips. The consolidation is done by pre-heating the chips at 200°C upto four passes through processing route BC. The maximum density of 99% and hardness of 94 HV was obtained after 4 ECAP passes. Tribological properties is evaluated by Pin-on-disc dry wear testing for three different loads at a constant sliding speed 750 RPM and distance of 5 kms. Chip consolidated CP Al is inferior in wear resistance with as-received CP Al owed to localised debonding of chips with the sliding disc.
Effect of Calcium Phosphate on Tensile and Rheological Properties of Polylactic Acid (PLA)
Authors: Sahu Govind , Rajput M.S. , Mahapatra S.P.
Published: August 2019

From the last few decades, biodegradable composites have become best alternatives over the petro based polymer because these degrade in the simple compound in the natural environments. Among the available biodegradable polymers, polylactic acid (PLA) is more popular due to its biocompatibility and mechanical properties, that can be used in the biomedical application, such as sutures, bone and ligament fixation screws etc. In this study, synthesis of PLA was performed by ring opening polymerization and Calcium phosphate/Polylactic acid (PLA) bio-composites were prepared by melt mixing technique. Tensile properties of these composites are investigated to assess its feasibility in biomedical and food packaging application.
Thermal Performance of Acrylonitrile Butadiene Styrene (ABS) Copolymer Blended with PTFE Particle/Polymer Composite
Authors: Kumar R. Mahesh , Rajini N. , Mayandi K. , Siengchin Suchart
Published: August 2019

Acrylonitrile Butadiene Styrene (ABS) polymer and Polytetrafluroethylene (PTFE) polymer has different properties individually. In this work ABS is used as matrix and PTFE is used as particle reinforcement. ABS is a copolymer containing butadiene, styrene and acrylonitrile. This work is to focus about the thermal property of ABS copolymer by adding PTFE as particle in polymer composites. From the analysis PTFE fit into a perfect particle reinforcement material for a broad assortment of utilizations. The samples is prepared with 100% ABS and 10% PTFE by weight, 20% PTFE is added to ABS and fabricated with Injection molding process. The addition of PTFE to ABS has improved on thermal properties. Experiment results shows that PTFE filler added composites exhibited high thermal conductivities and good coefficient of linear thermal expansion when compared with pure ABS copolymer.
Combustion Characteristics of Single Cylinder Diesel Engine Fueled with Blends of Thumba Biodiesel as an Alternative Fuel
Authors: Singh Manpreet , Sheikh Mohd Yunus , Singh Dharmendra , Rao P. Nageswara
Published: August 2019

The rapid rise in energy requirement and problem regarding atmosphere pollutions, renewable biofuels are the better alternative choice for the internal combustion engine to partially or totally replace the pollutant petroleum fuel. In the present work, thumba (Citrullus colocynthis) non-edible vegetable oil is used for the production of biodiesel and examine its possibility as diesel engine fuel. Transesterification process is used to produce biodiesel from thumba non-edible vegetable oil. Thumba biodiesel (TBD) is used to prepare five different volume concentration (blends) with neat diesel (D100), such as TBD5, TBD15, TBD25, TBD35 and TBD45 to run a single cylinder diesel engine. The diesel engine's combustion parameter such as in-cylinder pressure, rate of pressure rise, net heat release rate, cumulative heat release, mean gas temperature, and mass fraction burnt analyzed through graphs and compared all thumba biodiesel blends result with neat diesel fuel. The mass fraction burnt start earlier for thumba biodiesel blends compared to diesel fuel because of less ignition delay while peak in-cylinder pressure, maximum rate of pressure rise, maximum net heat release rate, maximum cumulative heat release, and maximum mean gas temperature has found decreased results up to 1.93%, 5.53%, 4.11%, 4.65%, and 1.73% respectively for thumba biodiesel.
Experimental Investigation of Proton Exchange Membrane (PEM) Fuel Cell Using Different Serpentine Flow Channels
Authors: Adari Matha Prasad , Lavanya P. , Hara Gopal P. , Sagar T.Praveen , Pavani S.
Published: August 2019

Proton exchange membrane fuel cell (PEMFC) system is an advanced power system for the future that is sustainable, clean and environmental friendly. The flow channels present in bipolar plates of a PEMFC are responsible for the effective distribution of the reactant gases. Uneven distribution of the reactants can cause variations in current density, temperature, and water content over the area of a PEMFC, thus reducing the performance of PEMFC. By using Serpentine flow field channel, the performance is increased. Two types of serpentine flow field channels are implemented such as curved serpentine flow field channel and normal serpentine flow field channels. The result shows that curved serpentine flow field channel gives better current density and power density, thus increasing the performance of PEMFC.
Improvement in Mechanical and Metallurgical Properties of Friction Stir Welded 6061-T6 Aluminum Alloys through Cryogenic Treatment
Authors: Babu K. Tejonadha , Muthukumaran S. , Kumar C.H. Bharat , Narayanan C. Sathiya
Published: August 2019

An investigation has been made to improve the properties of the friction stir welded (FSW) 6061-T6 aluminum alloys. A cryogenic thermal treatment is developed for the joints during welding and its effects on mechanical and metallurgical properties, and precipitates are evaluated at various welding parameters. The friction stir welded joints with cryogenic treatment attained the better properties than the without cryogenic treatment. The improvement of properties was attributed to the refinement of grain size and to the introduction of a reduction in the softening region of the welded joints. Under cryogenic cooling rates, joints were experienced to the low temperature environments and faster cooling rates, which are contributed to enhance the hardness of the stir zone and heat affected zone regions and the formation of ﬁne grain structure in the stir zone. The results indicated that the formation of finer grains of less than 5 µm in the stir zone, which is smaller than the joints of without cryogenic treatment. Subsequently, mechanical properties drastically improved and the joints achieved a maximum joint efficiency of 74% of the base material
Computational Fluid Dynamic Analysis on PEM Fuel Cell Performance Using Bio Channel
Authors: Badduri Srinivasa Reddy , Srinivasulu G. Naga , Rao S. Srinivasa
Published: August 2019

A 3-D computational model was developed to examine the proton exchange membrane fuel cell (PEMFC) performance using Bio inspired (Bio channel) flow channel design bipolar plate. The model was developed using ANSYS FLUENT-15.0 software and simulations were carried out at 100 % humidity conditions. The parameters such as pressure distribution, hydrogen and oxygen concentrations and proton conductivity were briefly presented. The simulation results of bio channel are presented in the form of polarization curves. The results of a Bio channel compare with the conventional flow channel and observed that the bio channel gives a less pressure drop, uniform distribution of reactants and high cell voltage at a particular current density. From the observation from the polarization data, the bio channel performance was 20% higher than triple serpentine flow channel.
Prediction and Optimization of Deformations in Coupling Mechanism Based Laser Forming of Sheet Metals
Authors: MAJI KUNTAL
Published: August 2019

Fabricating three dimensional shaped surfaces from flat sheet metals by laser forming, both out-of-plane and in-plane deformations are required. This article presents the modeling of coupling mechanism activated laser forming of sheet metals based on experimental data for prediction and optimization of bending and thickening deformations. Experiments were performed based on a central composite design of experiments on coupling mechanism based laser metal forming process considering the input process parameters like laser power, scan speed and spot diameter, bending and thickening were taken as the outputs. Neural network and neuro-fuzzy system-based models were developed to carry out both forward and inverse modeling of the laser metal forming process under the coupling mechanism. Multi-objective optimization based on the non-dominated sorting genetic algorithm was used to obtain multiple optimal solutions to achieve different amounts of out-of-plane and in-plane deformations. The proposed method could guide for a suitable selection of the process parameters to produce three-dimensional shapes utilizing coupling mechanism-based laser forming using multiple laser line heating.
Optimization of Cutting Conditions for Surface Roughness in VMC 5-Axis
Authors: Rudrapati Ramesh , Patil Arun
Published: August 2019

Vertical machining center (VMC) five-axis is advanced metal cutting process which used tomachine advanced materials for creating parts for industries like die, automotive, aerospace, machinerydesign, etc. Input parameters selection very important in VMC-five axis to obtain better surface finishon milled part and enhanced machining economics. In the present work, experimental analysis has beenplanned to study the significances of milling parameters on quality response, surface roughness (Ra) ofD3 steel. The experiments have been planned on D3 steel in VMC five axis as per Box-Behnken designof response surface methodology (RSM). Modeling and optimization have been done by hybrid RSMand Jaya optimization algorithm. The factor effects on Ra has been studied by analysis of signal-tonoise ratio. The concluding remarks has been drawn from the study
Performance Evaluation of Yield Function and Comparison of Yielding Characteristics of SS 304 in Annealed and Unannealed Conditions
Authors: Sivam S.P. Sundar Singh , Loganathan Ganesh Babu , Kumaran D. , Saravanan K. , Rajendra Kumar S.
Published: August 2019

Sheet metal forming forms in numerous industries like vehicle depend on the yielding of the sheet metals when strained. Yielding is portrayed by plastic flow of the materials when strained. The yield point if there should be an occurrence of uniaxial tension can be effectively decided from the pressure strain diagram, yet if there should arise an occurrence of multi axial Stresses it gets complicated. A connection between the principal stresses is required determining the conditions under which plastic flow occurs. This intricacy is tended to by the anisotropic yield capacities. Likewise, the tests used to acquire yield loci might be costly and time taking in such case these yield capacities end up being exceptionally viable. The yield criteria additionally help in deciding planar distribution of yield stresses and anisotropic coefficients, which gives a decent gauge of these mechanical parameters without having to through the pain of trial assurance. This project aims at using Hill 1948 criterion to obtain the Yield surface Diagrams for SS304 in annealed and original state and subsequently obtain the planar distribution of the uniaxial yield stress and anisotropic coefficient. Also, the performance evaluation of both the distributions will be done using accuracy index.
Some Preliminary Experimental Investigations on Inconel-718 Alloy with Rotary Tool-Electrode Assisted EDM
Authors: Kumar Rakesh , Pandey Anand , Sharma Pooja
Published: August 2019

In this paper, some preliminary experimental investigations have been reported for analysing the machining performance characteristics viz. Material Removal Rate (MRR) & Tool Wear Rate (TWR). Electrical Discharge Machining (EDM) of Inconel-718 alloy via helical threaded cryogenically treated rotary copper tool electrode is conducted. Impact of machining factors viz. peak current (Ip), pulse-on time (Ton), tool rotation (Nt) & hole depth (h) were investigated using Taguchi’s L9 (34) Orthogonal Array (OA). Optimum arrangements of factors for greatest MRR & least TWR were found in current study. Results predicts that Ip & Nt are two most affecting machining factors that affects MRR. Whereas Ip & Ton are two most affecting machining factors that affects TWR.
Synthesis of Al5083 Alloy by High Energy Ball Mill and Densification through Equal Channel Angular Pressing (ECAP)
Authors: Chandra Sekhar K. , Ravisankar Balasubramanian , Kumaran S.
Published: August 2019

An attempt was made to synthesis Al-5083alloy through high energy ball milling and densification through ECAP. The elemental powders consisting of Al5083 was milled for 5, 10 and 15 hrs using Retsch high energy ball mill (PM400). The physical and structural properties of mechanically alloyed particulates were characterised by diffraction methods and electron microscopy. The 15hrs nanocrystalline structured particulates of Al5083 alloy shows crystallite size of 15nm. Scanning Electron Microscope (SEM) reveals the morphology of alloy which is irregular shaped. The size of alloyed particulates also measured using SEM and found to be 7μm for 15hrs of milling. The 15hr milled alloy particulates were densified by ECAP through 90o die channel angle. Maximum densification of 92% and highest hardness of 63HRB was achieved for sample consolidated with route-A for two passes along with sintering.
Modelling of Tool Wear for Ti64 Turning Operation
Authors: Kumar Pawan , Misra J.P.
Published: August 2019

In this study, an attempt has been made to develop a predictive model for tool nose wear. A well planned experimental design was utilized for this purpose using the design of experiment approach. From this research work, it was found that cutting speed (s), feed (f) and their interaction having the main effect on cutting tool performance. Using ANOVA analysis significance and contribution of each machining parameter and their interaction is also analyzed. Hence, a predictive model was developed to predict tool nose wear by using the various machining parameters and its adequacy was also checked for the prediction purpose.
Analysis of Product Quality through Mechanical Properties and Determining Optimal Process Parameters of Untreated and Heat Treated Aisi 1050 Alloy during Turning Operation
Authors: Sivam S.P. Sundar Singh , Loganathan Ganesh Babu , Kumaran D. , Saravanan K. , Rajendra Kumar S.
Published: August 2019

AISI 1050 Alloy has a Wide Range of Applications and were Subjected to Machining Operations. the Purpose of the Study is to Find the Optimum Input Plain Turning Process Parameters at Three Levels, Using L18 Orthogonal Array and Grey Relation Analysis; and to Investigate the Mechanical and Microscopic Properties of the AISI 1050 Alloy before (untreated, UT) and after Annealing (AN) (heat-Treatment, HT) Process. the Results of Conducted Experiments Revealed the Optimum Process Parameters as Following for the Untreated Specimens: Spindle Speed at 3500 r.p.m., Feed 0.08 Mm/rev, Depth of Cut at 0.6 Mm, Insert Corner Radius at 4mm, and Cutting Fluid Concentration at 12 %, are the most Optimum Conditions to Obtain Minimum Power Consumption for the Untreated Specimens. whereas, a Spindle Speed at 3500 r.p.m., Feed at 0.08 Mm/rev, Depth of Cut at 0.6mm, Insert Corner Radius at 4 Mm, and Cutting Fluid Concentration at 12 % are the Optimum Parameter Values for the Treated Specimens.
Frequent Loss of IRF2 in Cancers Leads to Immune Evasion through Decreased MHC Class I Antigen Presentation and Increased PD-L1 Expression
Authors: Kriegsman Barry A. , Vangala Pranitha , Chen Benjamin J. , Meraner Paul , Brass Abraham L. , Garber Manuel , Rock Kenneth L.
Published: August 2019

To arise and progress, cancers need to evade immune elimination. Consequently, progressing tumors are often MHC class I (MHC-I) low and express immune inhibitory molecules, such as PD-L1, which allows them to avoid the main antitumor host defense, CD8+ T cells. The molecular mechanisms that led to these alterations were incompletely understood. In this study, we identify loss of the transcription factor IRF2 as a frequent underlying mechanism that leads to a tumor immune evasion phenotype in both humans and mice. We identified IRF2 in a CRISPR-based forward genetic screen for genes that controlled MHC-I Ag presentation in HeLa cells. We then found that many primary human cancers, including lung, colon, breast, prostate, and others, frequently downregulated IRF2. Although IRF2 is generally known as a transcriptional repressor, we found that it was a transcriptional activator of many key components of the MHC-I pathway, including immunoproteasomes, TAP, and ERAP1, whose transcriptional control was previously poorly understood. Upon loss of IRF2, cytosol-to–endoplasmic reticulum peptide transport and N-terminal peptide trimming become rate limiting for Ag presentation. In addition, we found that IRF2 is a repressor of PD-L1. Thus, by downregulating a single nonessential gene, tumors become harder to see (reduced Ag presentation), more inhibitory (increased checkpoint inhibitor), and less susceptible to being killed by CD8+ T cells. Importantly, we found that the loss of Ag presentation caused by IRF2 downregulation could be reversed by IFN-stimulated induction of the transcription factor IRF1. The implication of these findings for tumor progression and immunotherapy are discussed.
Long-Range Transport Mechanisms in East and Southeast Asia and Impacts on Size-Resolved Aerosol Composition: Contrasting High and Low Aerosol Loading Events
Authors: Braun Rachel A. , Aghdam Mojtaba Azadi , Bañaga Paola Angela , Betito Grace , Cambaliza Maria Obiminda , Cruz Melliza Templonuevo , Lorenzo Genevieve  Rose , MacDonald Alexander B. , Simpas James Bernard , Stahl Connor , Sorooshian Armin
Published: August 2019

Abstract. This study analyzes mechanisms of long-range transport of aerosol and aerosol chemical characteristics in and around East and Southeast Asia. Ground-based size-resolved aerosol measurements collected at the Manila Observatory in Metro Manila, Philippines from July–October 2018 were used to identify and contrast high and low aerosol loading events. Multiple data sources, including models, remote-sensing, and in situ measurements, are used to analyze the impacts of long-range aerosol transport on Metro Manila and the conditions at the local and synoptic scales facilitating this transport. Evidence of long-range transport of biomass burning aerosol from the Maritime Continent was identified through model results and the presence of biomass burning tracers (e.g. K, Rb) in the ground-based measurements. The impacts of emissions transported from continental East Asia are also identified; for one of the events analyzed, this transport was facilitated by the nearby passage of a typhoon. Changes in the aerosol size distributions, water-soluble chemical composition, and contributions of various organic aerosol species to the total water-soluble organic aerosol were examined for the different cases. The events impacted by biomass burning transport had the overall highest concentration of water-soluble organic acids, while the events impacted by long-range transport from continental East Asia, showed high percent contributions from shorter chain dicarboxylic acids (i.e. oxalate) that are often representative of photochemical and aqueous processing in the atmosphere. The low aerosol loading event was subject to a larger precipitation accumulation than the high aerosol events, indicative of wet scavenging as an aerosol sink in the study region. This low aerosol event was characterized by a larger relative contribution from supermicrometer aerosols and had a higher percent contribution from longer-chain dicarboxylic acids (i.e. maleate) to the water-soluble organic aerosol fraction. Results of this study have implications for better understanding of the transport and chemical characteristics of aerosol in a highly-populated region that has thus far been difficult to measure through remote-sensing methods. Furthermore, findings associated with the effects of air mass mixing on aerosol physiochemical properties are applicable to other global regions impacted by both natural and anthropogenic sources.
CAFE: a new, improved nonresonant laser-induced fluorescence instrument for airborne in situ measurement of formaldehyde
Authors: St. Clair Jason M. , Swanson Andrew K. , Bailey Steven A. , Hanisco Thomas F.
Published: August 2019

Abstract. NASA Compact Airborne Formaldehyde Experiment (CAFE) is a
nonresonant laser-induced fluorescence instrument for airborne in situ
measurement of formaldehyde (HCHO). The instrument is described here with
highlighted improvements from the predecessor instrument, COmpact
Formaldehyde FluorescencE Experiment (COFFEE). CAFE uses a 480 mW, 80 kHz
laser at 355 nm to excite HCHO and detects the resulting fluorescence in the
420–550 nm range. The fluorescence is acquired at 5 ns resolution for 500 ns
and the unique time profile of the HCHO fluorescence provides measurement
selectivity. CAFE achieves a 1σ precision of 160 pptv (1 s) and 90 pptv (10 s) for [HCHO] = 0 pptv. The accuracy of CAFE, using its
curve-fitting data processing, is estimated as ±20 % of [HCHO] + 100 pptv. CAFE has successfully flown on multiple aircraft platforms and is
particularly well-suited to high-altitude research aircraft or small air
quality research aircraft where high sensitivity is required but operator
interaction and instrument payload is limited.
Development and validation of a supervised machine learning radar Doppler spectra peak-finding algorithm
Authors: Kalesse Heike , Vogl Teresa , Paduraru Cosmin , Luke Edward
Published: August 2019

Abstract. In many types of clouds, multiple hydrometeor populations can be present at the same time and height. Studying the evolution of these different hydrometeors in a time–height perspective can give valuable information on cloud particle composition and microphysical growth processes. However, as a prerequisite, the number of different hydrometeor types in a certain cloud volume needs to be quantified. This can be accomplished using cloud radar Doppler velocity spectra from profiling cloud radars if the different hydrometeor types have sufficiently different terminal fall velocities to produce individual Doppler spectrum peaks. Here we present a newly developed supervised machine learning radar Doppler spectra peak-finding algorithm (named PEAKO). In this approach, three adjustable parameters (spectrum smoothing span, prominence threshold, and minimum peak width at half-height) are varied to obtain the set of parameters which yields the best agreement of user-classified and machine-marked peaks. The algorithm was developed for Ka-band ARM zenith-pointing radar (KAZR) observations obtained in thick snowfall systems during the Atmospheric Radiation Measurement Program (ARM) mobile facility AMF2 deployment at Hyytiälä, Finland, during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) field campaign. The performance of PEAKO is evaluated by comparing its results to existing Doppler peak-finding algorithms. The new algorithm consistently identifies Doppler spectra peaks and outperforms other algorithms by reducing noise and increasing temporal and height consistency in detected features. In the future, the PEAKO algorithm will be adapted to other cloud radars and other types of clouds consisting of multiple hydrometeors in the same cloud volume.
Validation, comparison, and integration of GOCI, AHI, MODIS, MISR, and VIIRS aerosol optical depth over East Asia during the 2016 KORUS-AQ campaign
Authors: Choi Myungje , Lim Hyunkwang , Kim Jhoon , Lee Seoyoung , Eck Thomas F. , Holben Brent N. , Garay Michael J. , Hyer Edward J. , Saide Pablo E. , Liu Hongqing
Published: August 2019

Abstract. Recently launched multichannel geostationary Earth orbit (GEO) satellite
sensors, such as the Geostationary Ocean Color Imager (GOCI) and the Advanced
Himawari Imager (AHI), provide aerosol products over East Asia with high
accuracy, which enables the monitoring of rapid diurnal variations and the
transboundary transport of aerosols. Most aerosol studies to date have used
low Earth orbit (LEO) satellite sensors, such as the Moderate Resolution
Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging
Spectroradiometer (MISR), with a maximum of one or two overpass daylight
times per day from midlatitudes to low latitudes. Thus, the demand for new GEO
observations with high temporal resolution and improved accuracy has been
significant. In this study the latest versions of aerosol optical depth
(AOD) products from three LEO sensors – MODIS (Dark Target, Deep Blue, and
MAIAC), MISR, and the Visible/Infrared Imager Radiometer Suite
(VIIRS), along with two GEO sensors (GOCI and AHI), are validated,
compared, and integrated for a period during the Korea–United States Air
Quality Study (KORUS-AQ) field campaign from 1 May to 12 June 2016 over East
Asia. The AOD products analyzed here generally have high accuracy with high
R (0.84–0.93) and low RMSE (0.12–0.17), but their error characteristics differ
according to the use of several different surface-reflectance estimation
methods. High-accuracy near-real-time GOCI and AHI measurements facilitate
the detection of rapid AOD changes, such as smoke aerosol transport from
Russia to Japan on 18–21 May 2016, heavy pollution transport from China to
the Korean Peninsula on 25 May 2016, and local emission transport from the Seoul
Metropolitan Area to the Yellow Sea in South Korea on 5 June 2016. These
high-temporal-resolution GEO measurements result in more representative
daily AOD values and make a greater contribution to a combined daily AOD
product assembled by median value selection with a 0.5∘×0.5∘ grid resolution. The combined AOD is spatially continuous and has
a greater number of pixels with high accuracy (fraction within expected
error range of 0.61) than individual products. This study characterizes
aerosol measurements from LEO and GEO satellites currently in operation over
East Asia, and the results presented here can be used to evaluate satellite
measurement bias and air quality models.
Characterising low-cost sensors in highly portable platforms to quantify personal exposure in diverse environments
Authors: Chatzidiakou Lia , Krause Anika , Popoola Olalekan A. M. , Di Antonio Andrea , Kellaway Mike , Han Yiqun , Squires Freya A. , Wang Teng , Zhang Hanbin , Wang Qi , Fan Yunfei , Chen Shiyi , Hu Min , Quint Jennifer K. , Barratt Benjamin , Kelly Frank J. , Zhu Tong , Jones Roderic L.
Published: August 2019

Abstract. The inaccurate quantification of personal exposure to air
pollution introduces error and bias in health estimations, severely limiting
causal inference in epidemiological research worldwide. Rapid advancements
in affordable, miniaturised air pollution sensor technologies offer the
potential to address this limitation by capturing the high variability of
personal exposure during daily life in large-scale studies with
unprecedented spatial and temporal resolution. However, concerns remain
regarding the suitability of novel sensing technologies for scientific and
policy purposes. In this paper we characterise the performance of a portable
personal air quality monitor (PAM) that integrates multiple miniaturised
sensors for nitrogen oxides (NOx), carbon monoxide (CO), ozone
(O3) and particulate matter (PM) measurements along with temperature,
relative humidity, acceleration, noise and GPS sensors. Overall, the air
pollution sensors showed high reproducibility (mean R‾2=0.93, min–max: 0.80–1.00) and excellent agreement with
standard instrumentation (mean R‾2=0.82, min–max: 0.54–0.99) in outdoor, indoor and commuting
microenvironments across seasons and different geographical settings. An
important outcome of this study is that the error of the PAM is
significantly smaller than the error introduced when estimating personal
exposure based on sparsely distributed outdoor fixed monitoring stations.
Hence, novel sensing technologies such as the ones demonstrated here can
revolutionise health studies by providing highly resolved reliable exposure
metrics at a large scale to investigate the underlying mechanisms of the
effects of air pollution on health.
Estimating the fate of oxygen ion outflow from the high altitude cusp
Authors: Krcelic Patrik , Haaland Stein , Maes Lukas , Slapak Rikard , Schillings Audrey
Published: August 2019

Abstract. We have investigated the oxygen escape-to-capture ratio from the high altitude cusp regions for various geomagnetic activity levels by combining EDI and CODIF measurements from the Cluster spacecraft. Using Tsyganenko model, we traced the observed oxygen ions to one of three regions: plasma sheet, solar wind beyond distant X-line or dayside magnetosheath. Our results indicate that 69 % of high altitude oxygen escapes the magnetosphere, from which most escape beyond the distant X-line (50 % of total oxygen flux). Convection of oxygen to the plasma sheet shows a strong dependence on geomagnetic activity. We used the Dst index as a proxy for geomagnetic storms and separated data into quiet conditions (Dst>0 nT), moderate conditions (0>Dst>−20 nT), and active conditions (Dst
Signatures of red-shifted foot points in the quiescent coronal loop system
Authors: Rao Yamini K. , Srivastava Abhishek K. , Kayshap Pradeep , Dwivedi Bhola N.
Published: August 2019

Abstract. We observed quiescent coronal loops using multi-wavelength observations from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) on 13 April 2016. The flows at the foot points of such loop systems are studied using spectral data from the Interface Region Imaging Spectrograph (IRIS). The Doppler velocity distributions at the foot points lying in the moss region show the negligible or small flows at the Ni I, Mg II k3, and C II line corresponding to upper photospheric and chromospheric emissions. Significant red shifts (downflows) ranging from 1 to 7 km s−1 are observed at Si IV (1393.78 Å; log⁡(T/K)=4.8), which is found to be consistent with the existing results regarding dynamical loop systems and moss regions. Such downflows agree well with the impulsive heating mechanism reported earlier.
Temporal variability in foraminiferal morphology and geochemistry at the West Antarctic Peninsula: a sediment trap study
Authors: Mikis Anna , Hendry Katharine R. , Pike Jennifer , Schmidt Daniela N. , Edgar Kirsty M. , Peck Victoria , Peeters Frank J. C. , Leng Melanie J. , Meredith Michael P. , Jones Chloe L. C. , Stammerjohn Sharon , Ducklow Hugh
Published: August 2019

Abstract. The West Antarctic Peninsula (WAP) exhibits strong spatial and temporal oceanographic variability, resulting in highly heterogeneous biological productivity. Calcifying organisms that live in the waters off the WAP respond to temporal and spatial variations in ocean temperature and chemistry. These marine calcifiers are potentially threatened by regional climate change with waters already naturally close to carbonate undersaturation. Future projections of carbonate production in the Southern Ocean are challenging due to the lack of historical data collection and complex, decadal climate variability. Here we present a 6-year-long record of the shell fluxes, morphology and stable isotope variability of the polar planktic foraminifera Neogloboquadrina pachyderma (sensu stricto) from near Palmer Station, Antarctica. This species is fundamental to Southern Ocean planktic carbonate production as it is one of the very few planktic foraminifer species adapted to the marine polar environments. We use these new data to obtain insights into its ecology and to derive a robust assessment of the response of this polar species to environmental change. Morphology and stable isotope composition reveal the presence of different growth stages within this tightly defined species. Inter- and intra-annual variability of foraminiferal flux and size is evident and driven by a combination of environmental forcing parameters, most importantly food availability, temperature and sea ice duration and extent. Foraminiferal growth occurs throughout the austral year and is influenced by environmental change, a large portion of which is driven by the Southern Annular Mode and El Niño–Southern Oscillation. A distinct seasonal production is observed, with the highest shell fluxes during the warmest and most productive months of the year. The sensitivity of calcifying foraminifera to environmental variability in this region, from weeks to decades, has implications both for their response to future climatic change and for their use as palaeoclimate indicators. A longer ice-free season could increase carbonate production in this region at least while carbonate saturation is still high enough to allow for thick tests to grow.
The Arctic picoeukaryote Micromonas pusilla benefits from Ocean Acidification under constant and dynamic light
Authors: White Emily , Hoppe Clara J. M. , Rost Björn
Published: August 2019

Abstract. Compared to the rest of the globe, the Arctic Ocean is affected disproportionately by climate change. Despite these fast environmental changes, we currently know little about the effects of ocean acidification (OA) on marine key species in this area. Moreover, the existing studies typically test the effects of OA under constant, hence artificial light fields. In this study, the abundant Arctic picoeukaryote Micromonas pusilla was acclimated to current (400 μatm) and future (1000 μatm) pCO2 levels under a constant as well as dynamic light, simulating natural light fields as experienced in the upper mixed layer. To describe and understand the responses to these drivers, growth, particulate organic carbon (POC) production, elemental composition, photophysiology and reactive oxygen species (ROS) production were analysed. M. pusilla was able to benefit from OA on various scales, ranging from an increase in growth rates to enhanced photosynthetic capacity, irrespective of the light regime. These beneficial effects were, however, not reflected in the POC production rates, which can be explained by energy partitioning towards cell division rather than biomass build-up. In the dynamic light regime, M. pusilla was able to optimise its photophysiology for effective light usage during both low and high light periods. This effective photoacclimation, which was achieved by modifications to photosystem II (PSII), imposed high metabolic costs leading to a reduction in growth and POC production rates when compared to constant light. There were no significant interactions observed between dynamic light and OA, indicating that M. pusilla was able maintain effective photoacclimation without increased photoinactivation under high pCO2. Based on these findings, physiologically plastic M. pusilla may exhibit a robust positive response to future Arctic Ocean conditions.
Efficient multi-scale Gaussian process regression for massive remote sensing data with satGP v0.1
Authors: Susiluoto Jouni , Spantini Alessio , Haario Heikki , Marzouk Youssef
Published: August 2019

Abstract. Satellite remote sensing provides a global view to processes on Earth that has unique benefits compared to measurements made on the ground. The global coverage and the enormous amounts of data produced come, however, with the price of spatial and temporal gaps and less than perfect data quality. Meaningful statistical inference from such data requires overcoming these problems and that calls for developing efficient computational tools. We design and implement a computationally efficient multi-scale Gaussian process (GP) software package, satGP, geared towards remote sensing applications. The software is designed to be able to handle problems of enormous sizes and is able to compute marginals and sample from a random process with at least over hundred million observations. The mean function of the Gaussian process is described by approximating marginals of a Markov random field (MRF). For covariance functions, Matern, exponential, and periodic kernels are utilized in a multi-scale kernel setting to describe the spatial heterogeneity present in data. We further demonstrate how winds can be used to inform the covariance kernel formulation. The covariance kernel parameters are learned by calculating an approximate marginal maximum likelihood estimate and this is utilized to verify the validity of the multi-scale approach in synthetic experiments. For demonstrating the techniques above, data from the Orbiting Carbon Observatory 2 (OCO-2) satellite is used. The satGP program is released as open source software.
COSMO-BEP-Tree v1.0: a coupled urban climate model with explicit representation of street trees
Authors: Mussetti Gianluca , Brunner Dominik , Henne Stephan , Allegrini Jonas , Krayenhoff E. Scott , Schubert Sebastian , Feigenwinter Christian , Vogt Roland , Wicki Andreas , Carmeliet Jan
Published: August 2019

Abstract. Street trees are more and more regarded as an effective measure to reduce excessive heat in urban areas. However, the vast majority of mesoscale urban climate models do not represent street trees in an explicit manner and for example do not take the important effect of shading by trees into account. In addition, urban canopy models that take interactions of trees and urban fabrics directly into account are usually limited to the street or neighbourhood scale and, hence, cannot be used to analyse the citywide effect of urban greening. In order to represent the interactions between street trees, urban elements and the atmosphere in realistic regional weather and climate simulations, we coupled the vegetated urban canopy model BEP-Tree and the mesoscale weather and climate model COSMO. The performance and applicability of the coupled model, named COSMO-BEP-Tree, are demonstrated over the urban area of Basel, Switzerland, during the heatwave event of June–July 2015. Overall, the model compared well with measurements of individual components of the surface energy balance and with air and surface temperatures obtained from a flux tower, surface stations and satellites. Deficiencies were identified for night-time air temperature and humidity, which can mainly be traced back to limitations in the simulation of the night-time stable boundary layer in COSMO. The representation of street trees in the coupled model generally improved the agreement with observations. Street trees produced large changes in simulated sensible and latent heat flux, and wind speed. Within the canopy layer, the presence of street trees resulted in a slight reduction in daytime air temperature and a very minor increase in night-time air temperature. The model was found to realistically respond to changes in the parameters defining the street trees: leaf area density and stomatal conductance. Overall, COSMO-BEP-Tree demonstrated the potential of (a) enabling city-wide studies on the cooling potential of street trees and (b) further enhancing the modelling capabilities and performance in urban climate modelling studies.
Website – Spatial database for reservoir-triggered seismicity in Brazil
Authors: Sayão Eveline , França George , Holanda Maristela , Gonçalves Alexandro
Published: August 2019

Abstract. After confirming that impoundment of large reservoirs could cause earthquakes worldwide, studies on reservoir-triggered seismicity (RTS) have had a considerable scientific incentive. Most of the studies determined that the vertical load increase due to reservoir load, and the reduction of effective effort due to the increase in pore pressure, can modify the stress regime in the reservoir region, possibly triggering earthquakes. In addition, the RTS is conditioned by several factors such as pre-existing tectonic stresses, reservoir size/weight, area-specific geological and hydromechanical conditions, constructive interaction between the orientation of seismotectonic forces, and additional load caused by the reservoir. One of the major challenges for studying RTS is to identify and correlate the factors in the area of influence of the reservoir, capable of influencing the RTS process itself. To assist the research, it was created a spatial seismicity-triggered reservoir database (BDSDR) based on the specifications of the national spatial data infrastructure (INDE), for gathering data pertinent to the RTS study in the area of reservoirs. In this context, this work presents the procedures and results found in the data processing of seismotectonic factors (dam height, reservoir volume, geology, and seismicity level) and compared with the dams that triggered earthquakes and the Brazilian dam catalog, which was then updated from 26 to 30 cases. The results indicate that the occurrence of RTS increases significantly with dam height since dams less than 50 m high cause only 2 % of earthquakes while those higher than 100 m cause about 54 %. The reservoir volume also plays a role and it was estimated that RTS occurrence requires a limiting minimum value of 1 × 10−4 km3. There was no clear correlation between the geology and geological provinces with RTS. The delayed response time of the reservoirs represents 43 % of the total, that is, almost half of them have hydraulic behavior. The highest magnitude, 4.2, was observed for an event that occurred in a reservoir with a volume greater than 10−3 km3. As a practical result to assist the analysis by the general community, the web viewer RISBRA (Reservoir Induced Seismicity in Brazil) was developed to serve as an interactive platform for BDSDR data.
Tracking the spread of a passive tracer through Southern Ocean water masses
Authors: Zika Jan D. , Sallée Jean-Baptiste , Meijers Andrew , Naveira-Garabato Alberto , Watson Andrew J. , Messias Marie-Jose , King Brian
Published: August 2019

Abstract. A dynamically passive inert tracer was released in the interior South Pacific Ocean at latitudes of the Antarctic Circumpolar Current. Observational cross sections of the tracer were taken over four consecutive years as it drifted through Drake Passage and into the Atlantic Ocean. The tracer was released within a region of high salinity relative to surrounding waters at the same density. In the absence of irreversible mixing a tracer remains at constant salinity and temperature on an isopycnal surface. To investigate the process of irreversible mixing we analysed the tracer in potential density versus salinity-anomaly coordinates. Observations of high tracer concentration tended to be collocated with isopycnal salinity anomalies. With time an initially narrow peak in tracer concentration as a function of salinity at constant density, broadened with the tracer being found at ever fresher salinities, consistent with diffusion-like behaviour in that coordinate system. The second moment of the tracer as a function of salinity suggested an initial period of slow spreading for approximately 2 years in the Pacific, followed by more rapid spreading as the tracer entered Drake Passage and the Scotia Sea. Analysis of isopycnal salinity gradients based on the Argo programme suggests that part of this apparent change can be explained by changes in background salinity gradients while part of the change may be explained by geographical changes in background mixing.
Sinkholes and uvalas in evaporite karst: spatio-temporal development with links to base-level fall on the eastern shore of the Dead Sea
Authors: Watson Robert A. , Holohan Eoghan P. , Al-Halbouni Djamil , Saberi Leila , Sawarieh Ali , Closson Damien , Alrshdan Hussam , Abou Karaki Najib , Siebert Christian , Walter Thomas R. , Dahm Torsten
Published: August 2019

Abstract. Enclosed topographic depressions are characteristic of
karst landscapes on Earth. The developmental relationship between depression
types, such as sinkholes (dolines) and uvalas, has been the subject of debate,
mainly because the long developmental timescales in classical limestone
karst settings impede direct observation. Here we characterize the
morphometric properties and spatio-temporal development of ∼1150 sinkholes and five uvalas formed from ∼1980 to 2017 in
an evaporite karst setting along the eastern coast of the hypersaline Dead
Sea (at Ghor Al-Haditha, Jordan). The development of sinkhole populations
and individual uvalas is intertwined in terms of onset, evolution and
cessation. The sinkholes commonly develop in clusters, within which they may
coalesce to form compound or nested sinkholes. In general, however, the
uvalas are not defined by coalescence of sinkholes. Although each uvala
usually encloses several clusters of sinkholes, it develops as a
larger-scale, gentler and structurally distinct depression. The location of
new sinkholes and uvalas shows a marked shoreline-parallel migration with
time, followed by a marked shoreline-perpendicular (i.e. seaward) growth
with time. These observations are consistent with theoretical predictions of
karstification controlled by a laterally migrating interface between
saturated and undersaturated groundwater, as induced by the 35 m fall in the
Dead Sea water level since 1967. More generally, our observations indicate that
uvalas and the sinkhole populations within them, although morphometrically
distinct, can develop near-synchronously by subsidence in response to
subsurface erosion.