bluuebunny/crossref_metadata_2025 huggingface dataset:
Methodology for Quantification of the Roping Phenomena in 6xxx Automotive Car Body Sheet Alloys
Authors: Schäfer Carmen , Brinkman Henk- Jan , Engler Olaf , Nitzsche Gernot , Keller Stefan
Published: June 2014

An important aspect when Al sheets are to be used for visible outer car body panels is surface appearance. Some age-hardenable Al-Mg-Si alloys of the AA 6xxx series can suffer from a phenomenon called roping. Roping appears on a macroscopic scale and manifests itself as the development of ridges and valleys 90° to the original rolling direction with a wavelength ranging from 1 to 10 mm when the sheet is formed to typical parts like doors or hoods. In the past years Al industry has developed means to minimise roping by careful control of alloy composition and through appropriate thermo-mechanical processing schedule. The increasing use of aluminium for outer skin applications gives proof that these efforts were successful. However, the extent of roping, and further the judgment of the quality of the surface appearance has up to now been done on a qualitative basis with comparisons against reference samples, as there are no established experimental techniques and no established analysis procedures for the quantification of this phenomenon. The goal of such a methodology is to be able to quantify the extent of roping in 6xxx automotive car body sheet alloys and to correlate it to a visual appearance ranking of roping. In the present study, a novel combination of a characterisation technique with an evaluation method is used to characterize and evaluate the roping behavior in aluminum alloys. This approach combines these already individually existing methods to a powerful tool: the measurement of a 3D surface topography with a subsequent analysis by means of Fourier analysis. The analysis of various car body sheet grades by means of this technique for uniaxial and biaxial loading conditions is presented in this paper.
Cryogenic Temperature and Strain Rate Dependence of Mechanical Properties for Extruded AA6060 Alloys
Authors: Xu Ze Bing , Roven Hans Jørgen , Furu Trond , Jia Zhi Hong
Published: June 2014

Tensile properties and fracture behavior of an AA6060 alloy were investigated at room temperature (295K) and cryogenic temperature (77K). It was found that both ultimate tensile strength and elongation increased with decreasing temperature. In particular, the latter increased with increasing strain rate at 77K. The changes in mechanical properties were thought to be due to a higher working hardening rate at low temperature, while the effect of strain rate on strain hardening was obscure at both temperatures. The hardness after tensile testing at 77K increased due to an increased accumulated dislocation density. Fracture occurred in a semi-ductile transgranular manner at 295K, while a mixture of intergranular and transgranular mode with less slip localization occurred at 77K. Moreover, a decreased testing temperature led to a decreased size of dimples. The rotation of grain orientations can lead to increased Schmid factors and change of the latter was strongly dependent on the deformation temperature, which was clarified by compression tests.
Assessment of Deformation Behavior of Polycrystalline Aluminum Using Diffraction-Amalgamated Grain-Boundary Tracking (DAGT) Technique
Authors: Toda Hiroyuki , Kamiko Takanobu , Uesugi Kentaro , Takeuchi Akihisa , Suzuki Yoshio , Kobayashi Masakazu
Published: June 2014

A novel experimental method has been developed by amalgamating a pencil beam X-Ray diffraction (XRD) technique with the recently developed grain boundary tracking (GBT) technique. XRD and GBT are both non-destructive in-situ analysis techniques for characterizing bulk materials, which can be carried out close to the point of fracture. DAGT provides information about individual grain orientations and 1-micron-level grain morphologies in 3-dimensions (3D) together with high-density local strain mapping. An Al-3 mass % Cu model alloy was used to investigate its deformation behavior under tension. The morphology of the grains was determined by the X-ray microtomography (XMT) imaging and the liquid metal wetting technique, after which GBT provided an accurate description of the position and morphology of all the grains in a region of interests. Diffraction spots in the XRD experiments were related to grains, making it possible to describe crystallographic orientation of all the grains. It has been revealed that deformation is localized at both microscopic and meso-scopic levels. Inhomogeneous deformation was observed in each individual grain. In addition, a group of a few grains coordinately interacts and specific grain boundaries thereby exhibit intense strain localization. Hydrostatic tension was also observed at quadruple junction points and its mechanism was analyzed.
Application of the Nes Model for Static Recovery of the Dislocation Density in Cold Rolled AA6XXX
Authors: Penlington Alex , Diak Bradley , Jin Hai Ou
Published: June 2014

An experimental 6XXX series aluminum alloy, Al-0.4Mg-1.2Si-0.49Cu-0.14Mn-0.2Fe(wt.%), was cold rolled 73% and the kinetics of its static recovery studied isochronally between 80 to 350°C, and isothermally at 175 and 205°C. Typical recovery is described by an extrinsic property such as yield stress, however, this study utilized the intrinsic dislocation density extracted from x-ray line profile analysis using a modified Williamson-Hall analysis. The static recovery of dislocation density was fit to the models of Nes [Acta Metall. Mater. 43 (1995) 2189–2207], suggesting that recovery is controlled by the migration of jogged screw dislocations assuming no lateral drift during annealing. The model fit of isothermal annealing at 175°C and 205°C yields activation energies of 0.99 and 1.7 eV/at., respectively. The change in energies can be correlated to an observed change in lattice strain with recovery.
Finite Element Modelling of the Temperature Dependent Low Cycle Fatigue Damage Mechanism of an AlSi12 Type Alloy
Authors: Eckmann Stefan , von Hartrott Philipp
Published: June 2014

Aluminium cast alloys are used for engine components, such as pistons and cylinder heads. The micromechanical properties of an AlSi12 cast alloy under monotonic and cyclic loadings are investigated. Therefore a microstructure-based two dimensional finite element model is generated. The characteristic shape of primary precipitates is analyzed and translated into an artificial microstructure. The quality of the generated microstructure is evaluated based on the stress distribution along the primary particle boundaries. The effect of the temperature dependent material behavior of the aluminium matrix is studied with respect to the resulting stress distribution along the particle boundaries. The results are discussed in terms of a possible change of fracture mechanisms from a brittle type fracture at low temperatures to an increasingly ductile fracture at high temperatures.
A Novel Methodology for Optimisation of Product Properties and Production Costs in Fabrication of Aluminium Alloys
Authors: Myhr Ole Runar , Østhus Rune , Furu Trond
Published: June 2014

The present paper describes a novel methodology for optimization of product properties and production costs in fabrication of aluminium alloys. The main idea is to represent each operation along the process chain by predictive tools, which include material-, mechanical-, cost-and logistics models. An optimisation tool is used to collect the simulation models into a common software environment, which allows fully automatic simulations to be carried out. When this coupling is established, the models are run in sequence using different types of optimisation strategies. The methodology has been applied for optimisation of strength, grain structure and costs of 6xxx series aluminium extrusions. The results indicate that the present methodology is sufficiently relevant and comprehensive to be used as a tool in fabrication of various aluminium products, for instance in optimisation of end-user properties and production costs of extruded, rolled or foundry based alloys.
Grain Refinement Mechanism of Al-5Ti-1B Master Alloy by Ab Initio Calculations
Authors: Zhang Han Long , Han Yan Feng , Wang Jun , Dai Yong Bing , Sun Bao De
Published: June 2014

To exactly understand the grain refining mechanism of α-Al by the Al-5Ti-1B master alloy, the structural properties of α-Al/solid-TiB2 (S/S) and liquid-Al/solid-TiB2 (L/S) interfaces were studied using the first-principles method. Different ordered structures were formed on the interfaces with different terminations of TiB2 (0001) surface, which determines the nucleant potency of TiB2. The heterogeneous nucleation of α-Al on the B-terminated surface is frustrated by an AlB2-like structure formed at the interface. In contrast, a five-layer quasi-solid region with stacking sequence of fcc-Al (111) planes forms on the Ti-terminated TiB2 (0001) surface, which is the basis of successful heterogeneous nucleation of α-Al. Moreover, when redundant Ti solute being added into the liquid Al region of Ti-terminated liquid-Al/TiB2 interface, the quasi-solid Al region further extends until entire solidification. The reason for using the Al-5Ti-1B master alloy rather than TiB2 powders as the commercial refiner in Al industry lies in two aspects: the excessive Ti atoms in the master alloy could guarantee sufficient Ti chemical potential to form Ti-terminated surface of TiB2, and the redundant Ti solute in inoculated melts could facilitate the growth of quasi-solid Al region at the solid/liquid interface.
Effect of Cold Plastic Deformation on Mechanical Properties of Aluminum Alloy 2519 After Ageing
Authors: Zuiko Ivan , Gazizov Marat , Kaibyshev Rustam
Published: June 2014

Effect of cold plastic deformation prior to ageing at 180°C on a microstructure and mechanical properties at room temperature for an AA2519 alloy was examined subjected to solution treatment and water quenching initially. It was found that cold rolling with a reduction of 15% or equal-channel angular pressing (ECAP) up to a true strain of ~1 leads to acceleration of age-hardening response of this alloy. Peak hardness values of 127, 175 and 169 HV0.2 were achieved by ageing following quenching, cold rolling and ECAP, respectively. The highest values of yield stress (YS) of 475 MPa and ultimate tensile strength (UTS) of 520 MPa, were attained after ECAP followed by ageing. The effect of cold plastic deformation prior to ageing on the precipitation behavior and its relation with mechanical properties of the AA2519 is discussed.
Use of Multicomponent Phase Diagrams for Designing High Strength Casting Aluminum Alloys
Authors: Belov Nikolay , Alabin A.N.
Published: June 2014

Principles of optimization of the phase constitution of a new group of aluminum alloys, i.e., sparingly alloyed high-strength casting nickalyns are considered. The Thermo-Calc software and experimental methods (LM, SEM, TEM, EPMA, etc.) were used for analyzing the phase constitution of the Al–Zn–Mg–Cu–Fe–Ni system as applied to high-strength (UTS>450 MPa) aluminum alloys based on (Al)+Al3Ni and (Al)+Al9FeNi eutectics. Both eutectics possess the fine structure but the latter is more expedient due to the lower content of nickel. Then the iron becomes an alloying component rather than a harmful impurity. It is shown that the addition of copper substantially complicates the phase constitution and strongly decreases the equilibrium solidus, which limits the possibility of carrying out the high temperature annealing. This can negatively affect the spheroidization of the Al3Ni and Al9FeNi phases. A set of calculated and experimental data is used to show the perspectives of replacement of the existing high-strength casting aluminum alloys based on Al–Cu system (AA201, 206, 224) by the sparingly alloyed low-copper weldable nickalyn Al6Zn0.5Ni.
Aging Precipitation of Al-Mg-Si Alloys with Additions of Ag and Cu
Authors: Nishikubo Masaya , Matsuda Kenji , Oe Yoshihisa , Nakamura Jyunya , Ikeno Susumu
Published: June 2014

In this study, the aging behaviour of several Al-Mg-Si alloys (Al-Mg-Si-Cu , Al-Mg-Si-Ag and Al-Mg-Si-Cu-Ag) has been investigated by hardness tests and TEM observations. Comparing the age-hardening rate in the early period of these alloys, the alloys with Cu or/and Ag addition are faster than that of the base alloy, and the aging time to reach the maximum hardness of the alloys with Cu or/and Ag addition is shorter than that of the base alloy.Therefore the aging behaviour of that alloys has been investigated by TEM observations to understand the effect of Cu, Ag and Cu+Ag additions on aging precipitation.
Thin-layer catalytic far-infrared radiation drying and flavour of tomato slices
Authors: Abano Ernest Ekow , Ma Hai Le , Qu Wenjuan
Published: June 2014

A far-infrared radiation (FIR) catalytic laboratory dryer was designed by us and used to dry tomato. The kinetics of drying of tomato slices with FIR energy was dependent on both the distance from the heat source and the sample thickness. Numerical evaluation of the simplified Fick’s law for Fourier number showed that the effective moisture diffusivity increased from 0.193×10–9 to 1.893×10–9 m2/s, from 0.059×10–9 to 2.885×10–9 m2/s, and, from 0.170×10–9 to 4.531×10–9 m2/s for the 7, 9, and 11 mm thick slices as moisture content decreased. Application of FIR enhanced the flavour of the dried tomatoes by 36.6% when compared with the raw ones. The results demonstrate that in addition to shorter drying times, the flavour of the products can be enhanced with FIR. Therefore, FIR drying should be considered as an efficient drying method for tomato with respect to minimization of processing time, enhancement in flavour, and improvements in the quality and functional property of dried tomatoes.
Price, availability and affordability of medicines
Authors: Mhlanga Brenda S. , Suleman Fatima
Published: June 2014

Background: Medicines play an important role in healthcare, but prices can be a barrier to patient care. Few studies have looked at the prices of essential medicines in low- and middle-income countries in terms of patient affordability.Aim: To determine the prices, availability and affordability of medicines along the supply chain in Swaziland.Setting: Private- and public-sector facilities in Manzini, Swaziland.Methods: The standardised methodology designed by the World Health Organization and Health Action International was used to survey 16 chronic disease medicines. Data were collected in one administrative area in 10 private retail pharmacies and 10 public health facilities. Originator brand (OB) and lowest-priced generic equivalent (LPG) medicines were monitored and these prices were then compared with international reference prices (IRPs). Affordability was calculated in terms of the daily wage of the lowest-paid unskilled government worker.Results: Mean availability was 68% in the public sector. Private sector OB medicines were priced 32.4 times higher than IRPs, whilst LPGs were 7.32 times higher. OBs cost473% more than LPGs. The total cumulative mark-ups for individual medicines range from 190.99% – 440.27%. The largest contributor to add-on cost was the retail mark-up (31% – 53%). Standard treatment with originator brands cost more than a day’s wage.Conclusion: Various policy measures such as introducing price capping at all levels of the medicine supply chain, may increase the availability, whilst at the same time reducing the prices of essential medicines for the low income population.
Comparing the Usefulness of the 1997 and 2009 WHO Dengue Case Classification: A Systematic Literature Review
Authors: Horstick Olaf , Jaenisch Thomas , Martinez Eric , Kroeger Axel , See Lucy Lum Chai , Farrar Jeremy , Ranzinger Silvia Runge
Published: June 2014

The 1997 and 2009 WHO dengue case classifications were compared in a systematic review with 12 eligible studies (4 prospective). Ten expert opinion articles were used for discussion. For the 2009 WHO classification studies show: when determining severe dengue sensitivity ranges between 59–98% (88%/98%: prospective studies), specificity between 41–99% (99%: prospective study) - comparing the 1997 WHO classification: sensitivity 24.8–89.9% (24.8%/74%: prospective studies), specificity: 25%/100% (100%: prospective study). The application of the 2009 WHO classification is easy, however for (non-severe) dengue there may be a risk of monitoring increased case numbers. Warning signs validation studies are needed. For epidemiological/pathogenesis research use of the 2009 WHO classification, opinion papers show that ease of application, increased sensitivity (severe dengue) and international comparability are advantageous; 3 severe dengue criteria (severe plasma leakage, severe bleeding, severe organ manifestation) are useful research endpoints. The 2009 WHO classification has clear advantages for clinical use, use in epidemiology is promising and research use may at least not be a disadvantage.
Effectiveness Trial of Community-Based I Choose Life-Africa Human Immunodeficiency Virus Prevention Program in Kenya
Authors: Adam Mary B.
Published: June 2014

We measured the effectiveness of a human immunodeficiency virus (HIV) prevention program developed in Kenya and carried out among university students. A total of 182 student volunteers were randomized into an intervention group who received a 32-hour training course as HIV prevention peer educators and a control group who received no training. Repeated measures assessed HIV-related attitudes, intentions, knowledge, and behaviors four times over six months. Data were analyzed by using linear mixed models to compare the rate of change on 13 dependent variables that examined sexual risk behavior. Based on multi-level models, the slope coefficients for four variables showed reliable change in the hoped for direction: abstinence from oral, vaginal, or anal sex in the last two months, condom attitudes, HIV testing, and refusal skill. The intervention demonstrated evidence of non-zero slope coefficients in the hoped for direction on 12 of 13 dependent variables. The intervention reduced sexual risk behavior.
Phylogeography of Rickettsia rickettsii Genotypes Associated with Fatal Rocky Mountain Spotted Fever
Authors: Paddock Christopher D. , Denison Amy M. , Lash R. Ryan , Liu Lindy , Bollweg Brigid C. , Dahlgren F. Scott , Kanamura Cristina T. , Angerami Rodrigo N. , Pereira dos Santos Fabiana C. , Brasil Martines Roosecelis , Karpathy Sandor E.
Published: June 2014

Rocky Mountain spotted fever (RMSF), a tick-borne zoonosis caused by Rickettsia rickettsii, is among the deadliest of all infectious diseases. To identify the distribution of various genotypes of R. rickettsii associated with fatal RMSF, we applied molecular typing methods to samples of DNA extracted from formalin-fixed, paraffin-embedded tissue specimens obtained at autopsy from 103 case-patients from seven countries who died of RMSF. Complete sequences of one or more intergenic regions were amplified from tissues of 30 (29%) case-patients and revealed a distribution of genotypes consisting of four distinct clades, including the Hlp clade, regarded previously as a non-pathogenic strain of R. rickettsii. Distinct phylogeographic patterns were identified when composite case-patient and reference strain data were mapped to the state and country of origin. The phylogeography of R. rickettsii is likely determined by ecological and environmental factors that exist independently of the distribution of a particular tick vector.
The Milestones Passport: A Learner-Centered Application of the Milestone Framework to Prompt Real-Time Feedback in the Emergency Department
Authors: Yarris Lalena M. , Jones David , Kornegay Joshua G. , Hansen Matthew
Published: June 2014

Background

In July 2013, emergency medicine residency programs implemented the Milestone assessment as part of the Next Accreditation System.

Objective

We hypothesized that applying the Milestone framework to real-time feedback in the emergency department (ED) could affect current feedback processes and culture. We describe the development and implementation of a Milestone-based, learner-centered intervention designed to prompt real-time feedback in the ED.

Methods

We developed and implemented the Milestones Passport, a feedback intervention incorporating subcompetencies, in our residency program in July 2013. Our primary outcomes were feasibility, including faculty and staff time and costs, number of documented feedback encounters in the first 2 months of implementation, and user-reported time required to complete the intervention. We also assessed learner and faculty acceptability.

Results

Development and implementation of the Milestones Passport required 10 hours of program coordinator time, 120 hours of software developer time, and 20 hours of faculty time. Twenty-eight residents and 34 faculty members generated 257 Milestones Passport feedback encounters. Most residents and faculty reported that the encounters required fewer than 5 minutes to complete, and 48% (12 of 25) of the residents and 68% (19 of 28) of faculty reported satisfaction with the Milestones Passport intervention. Faculty satisfaction with overall feedback in the ED improved after the intervention (93% versus 54%, P  =  .003), whereas resident satisfaction with feedback did not change significantly.

Conclusions

The Milestones Passport feedback intervention was feasible and acceptable to users; however, learner satisfaction with the Milestone assessment in the ED was modest.
The Pagami Creek smoke plume after long-range transport to the upper troposphere over Europe – aerosol properties and black carbon mixing state
Authors: Dahlkötter F. , Gysel M. , Sauer D. , Minikin A. , Baumann R. , Seifert P. , Ansmann A. , Fromm M. , Voigt C. , Weinzierl B.
Published: June 2014

Abstract. During the CONCERT 2011 field experiment with the DLR research aircraft Falcon, an enhanced aerosol layer with particle linear depolarization ratios of 6–8% at 532 nm was observed at altitudes above 10 km over northeast Germany on 16 September 2011. Dispersion simulations with HYSPILT suggest that the elevated aerosol layer originated from the Pagami Creek forest fire in Minnesota, USA, which caused pyro-convective uplift of particles and gases. The 3–4 day-old smoke plume had high total refractory black carbon (rBC) mass concentrations of 0.03–0.35 μg m−3 at standard temperature and pressure (STP) with rBC mass equivalent diameter predominantly smaller than 130 nm. Assuming a core-shell particle structure, the BC cores exhibit very thick (median: 105–136 nm) BC-free coatings. A large fraction of the BC-containing particles disintegrated into a BC-free fragment and a BC fragment while passing through the laser beam of the Single Particle Soot Photometer (SP2). In this study, the disintegration is a result of very thick coatings around the BC cores. This is in contrast to a previous study in a forest-fire plume, where it was hypothesized to be a result of BC cores being attached to a BC-free particle. For the high-altitude forest-fire aerosol layer observed in this study, increased mass specific light-absorption cross sections of BC can be expected due to the very thick coatings around the BC cores, while this would not be the case for the attached-type morphology. We estimate the BC mass import from the Pagami Creek forest fire into the upper troposphere/lower stratosphere (UTLS) region (best estimate: 25 Mg rBC). A comparison to black carbon emission rates from aviation underlines the importance of pyro-convection on the BC load in the UTLS region. Our study provides detailed information on the microphysics and the mixing state of BC in the forest-fire aerosol layer in the upper troposphere that can be used to better understand and investigate the radiative impact of such upper tropospheric aerosol layers.
Simulation of semi-explicit mechanisms of SOA formation from glyoxal in aerosol in a 3-D model
Authors: Knote C. , Hodzic A. , Jimenez J. L. , Volkamer R. , Orlando J. J. , Baidar S. , Brioude J. , Fast J. , Gentner D. R. , Goldstein A. H. , Hayes P. L. , Knighton W. B. , Oetjen H. , Setyan A. , Stark H. , Thalman R. , Tyndall G. , Washenfelder R. , Waxman E. , Zhang Q.
Published: June 2014

Abstract. New pathways to form secondary organic aerosol (SOA) have been postulated recently. Glyoxal, the smallest dicarbonyl, is one of the proposed precursors. It has both anthropogenic and biogenic sources, and readily partitions into the aqueous phase of cloud droplets and deliquesced particles where it undergoes both reversible and irreversible chemistry. In this work we extend the regional scale chemistry transport model WRF-Chem to include detailed gas-phase chemistry of glyoxal formation as well as a state-of-the-science module describing its partitioning and reactions in the aerosol aqueous-phase. A comparison of several proposed mechanisms is performed to quantify the relative importance of different formation pathways and their regional variability. The CARES/CalNex campaigns over California in summer 2010 are used as case studies to evaluate the model against observations. A month-long simulation over the continental United States (US) enables us to extend our results to the continental scale. In all simulations over California, the Los Angeles (LA) basin was found to be the hot spot for SOA formation from glyoxal, which contributes between 1% and 15% of the model SOA depending on the mechanism used. Our results indicate that a mechanism based only on a reactive (surface limited) uptake coefficient leads to higher SOA yields from glyoxal compared to a more detailed description that considers aerosol phase state and chemical composition. In the more detailed simulations, surface uptake is found to give the highest SOA mass yields compared to a volume process and reversible formation. We find that the yields of the latter are limited by the availability of glyoxal in aerosol water, which is in turn controlled by an increase in the Henry's law constant depending on salt concentrations ("salting-in"). A time dependence in this increase prevents substantial partitioning of glyoxal into aerosol water at high salt concentrations. If this limitation is removed, volume pathways contribute > 20% of glyoxal-SOA mass, and the total mass formed (5.8% of total SOA in the LA basin) is about a third of the simple uptake coefficient formulation without consideration of aerosol phase state and composition. Results from the continental US simulation reveal the much larger potential to form glyoxal-SOA over the eastern continental US. Interestingly, the low concentrations of glyoxal-SOA over the western continental US are not due to the lack of a potential to form glyoxal-SOA here. Rather these small glyoxal-SOA concentrations reflect dry conditions and high salt concentrations, and the potential to form SOA mass here will strongly depend on the water associated with particles.
Quasi-biennial oscillation of the tropical stratospheric aerosol layer
Authors: Hommel R. , Timmreck C. , Giorgetta M. A. , Graf H. F.
Published: June 2014

Abstract. This study describes how aerosol in an aerosol-coupled climate model of the middle atmosphere is influenced by the quasi-biennial oscillation (QBO) during times when the stratosphere is largely unperturbed from volcanic material. In accordance with satellite observations, the tropical stratospheric aerosol load is predominately influenced by QBO induced anomalies in the vertical advection. Large impacts are seen in the size of aerosols, in particular in the region where aerosol evaporates. This turns the quasi-static balance between processes maintaining the vertical extent of the Junge layer in the tropics into a cyclic balance when considering this dominant mode of atmospheric variability. Global aerosol-interactive models without a QBO are only able to simulate the quasi-static balance state. To assess the global impact of stratospheric aerosols on climate processes, those partly non-linear relationships between the QBO and stratospheric aerosols have to be taken into account.
Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium
Authors: De Bock V. , De Backer H. , Van Malderen R. , Mangold A. , Delcloo A.
Published: June 2014

Abstract. At Uccle, a long time series (1991–2013) of simultaneous measurements of erythemal ultraviolet (UV) dose, global solar radiation, total ozone column (TOC) and Aerosol Optical Depth (AOD) (at 320.1 nm) is available which allows for an extensive study of the changes in the variables over time. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for erythemal UV dose and TOC, a significant change point (without any known instrumental cause) was present in the time series around February 1998 and March 1998 respectively. The change point in TOC corresponds with results found in literature, where the change in ozone levels (around 1997) is attributed to the recovery of ozone. Linear trends were determined for the different (monthly anomalies) time series. Erythemal UV dose, global solar radiation and TOC all increase with respectively 7, 4 and 3% per decade. AOD shows an (insignificant) negative trend of −8% per decade. These trends agree with results found in literature for sites with comparable latitudes. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of global solar radiation, TOC and AOD on the erythemal UV dose. Together these parameters are able to explain 94% of the variation in erythemal UV dose. Most of the variation (56%) in erythemal UV dose is explained by global solar radiation. The regression model performs well with a slight tendency to underestimate the measured erythemal UV doses and with a Mean Absolute Bias Error (MABE) of 18%. However, in winter, negative erythemal UV dose values are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R2 value higher than 0.8 and the correlation between modeled and measured erythemal UV dose values is higher than 0.9 for each season. The summer model gives the best performance, with an absolute mean error of only 6%. Again, global solar radiation is the factor that contributes the most to the variation in erythemal UV dose, so there is no doubt about the necessity to include this factor in the regression models. A large part of the influence of AOD is already represented by the global solar radiation parameter. Therefore the individual contribution of AOD to erythemal UV dose is so low. For this reason, it seems unnecessary to include AOD in the MLR analysis. Including TOC however, is justified as the adjusted R2 increases and the MABE of the model decreases compared to a model where only global solar radiation is used as explanatory variable.
Neural network-based estimates of Southern Ocean net community production from in situ O2 / Ar and satellite observation: a methodological study
Authors: Chang C.-H. , Johnson N. C. , Cassar N.
Published: June 2014

Abstract. Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of one to two weeks and with six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This nonparametric approach is based entirely on the observed statistical relationships between NCP and the predictors and, therefore, is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published, independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the Subtropical Front in the Atlantic, Indian, and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, the Patagonian Shelf, the Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air–sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 17.9 mmol C m−2 d−1, falls within the range of 8.3 to 24 mmol C m−2 d−1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability.
Diversity of Arctic pelagic Bacteria with an emphasis on photoheterotrophs: a review
Authors: Boeuf D. , Humily F. , Jeanthon C.
Published: June 2014

Abstract. The Arctic Ocean is a unique marine environment with respect to seasonality of light, temperature, perennial ice cover, and strong stratification. Other important distinctive features are the influence of extensive continental shelves and its interactions with Atlantic and Pacific water masses and freshwater from sea ice melt and rivers. These characteristics have major influence on the biological and biogeochemical processes occurring in this complex natural system. Heterotrophic bacteria are crucial components of marine food webs and have key roles in controlling carbon fluxes in the oceans. Although it was previously thought that these organisms relied on the organic carbon in seawater for all of their energy needs, several recent discoveries now suggest that pelagic bacteria can depart from a strictly heterotrophic lifestyle by obtaining energy through unconventional mechanisms that are linked to the penetration of sunlight into surface waters. These photoheterotrophic mechanisms may play a significant role in the energy budget in the euphotic zone of marine environments. Modifications of light and carbon availability triggered by climate change may favor the photoheterotrophic lifestyle. Here we review advances in our knowledge of the diversity of marine photoheterotrophic bacteria and discuss their significance in the Arctic Ocean gained in the framework of the Malina cruise.
Microbial responses to chitin and chitosan in oxic and anoxic agricultural soil slurries
Authors: Wieczorek A. S. , Hetz S. A. , Kolb S.
Published: June 2014

Abstract. Microbial degradation of chitin in soil substantially contributes to carbon cycling in terrestrial ecosystems. Chitin is globally the second most abundant biopolymer after cellulose and can be deacetylated to chitosan or can be hydrolyzed to N,N′-diacetylchitobiose and oligomers of N-acetylglucosamine by aerobic and anaerobic microorganisms. Which pathway of chitin hydrolysis is preferred by soil microbial communities is unknown. Supplementation of chitin stimulated microbial activity under oxic and anoxic conditions in agricultural soil slurries, whereas chitosan had no effect. Thus, the soil microbial community likely was more adapted to chitin as a substrate. In addition, this finding suggested that direct hydrolysis of chitin was preferred to the pathway that starts with deacetylation. Chitin was apparently degraded by aerobic respiration, ammonification, and nitrification to carbon dioxide and nitrate under oxic conditions. When oxygen was absent, fermentation products (acetate, butyrate, propionate, hydrogen, and carbon dioxide) and ammonia were detected, suggesting that butyric and propionic acid fermentation, along with ammonification, were likely responsible for anaerobic chitin degradation. In total, 42 different chiA genotypes were detected of which twenty were novel at an amino acid sequence dissimilarity of less than 50%. Various chiA genotypes responded to chitin supplementation and affiliated with a novel deep-branching bacterial chiA genotype (anoxic conditions), genotypes of Beta- and Gammaproteobacteria (oxic and anoxic conditions), and Planctomycetes (oxic conditions). Thus, this study provides evidence that detected chitinolytic bacteria were catabolically diverse and occupied different ecological niches with regard to oxygen availability enabling chitin degradation under various redox conditions on community level.
Contrasting effects of invasive insects and fire on ecosystem water use efficiency
Authors: Clark K. L. , Skowronski N. S. , Gallagher M. R. , Renninger H. , Schäfer K. V. R.
Published: June 2014

Abstract. We used eddy covariance and meteorological measurements to estimate net ecosystem exchange of CO2 (NEEc), gross ecosystem production (GEP), evapotranspiration (Et), and ecosystem water use efficiency (WUEe) in three upland forests in the New Jersey Pinelands that were defoliated by Gypsy moth (Lymantria dispar L.) or burned using prescribed fire. Before disturbance daytime NEEc, daily GEP and daily WUEe during the summer were greater at an oak-dominated stand than at mixed or pine-dominated stands. Both defoliation and prescribed burning reduced stand leaf area and canopy nitrogen content. At the oak stand, daily GEP during the summer was only 35% of pre-disturbance values during complete defoliation in 2007, and then averaged 71% and 78% of pre-defoliation values one and two years following complete defoliation. Prescribed fires conducted in the dormant season at the mixed and pine-dominated stands reduced daily GEP during the summer to 79 and 82% of pre-disturbance periods during the following growing season. Daily GEP during the summer was a strong function of N content in foliage at the oak and mixed stands, but a weaker function at the pine-dominated stand. Ecosystem WUEe, calculated as GEP/Et during dry canopy conditions in the summer, was reduced to 60% and 46% of pre-disturbance values at the oak and mixed stands during defoliation, while prescribed fire had little effect on WUEe. Overall, our results indicate that WUEe during recovery is dependent on both the type and time since disturbance.
Methane related changes in prokaryotic activity along geochemical profiles in sediments of Lake Kinneret (Israel)
Authors: Bar Or I. , Ben-Dov E. , Kushmaro A. , Eckert W. , Sivan O.
Published: June 2014

Abstract. Microbial methane oxidation process (methanotrophy) is the primary control on the emission of the greenhouse gas methane (CH4) to the atmosphere. In terrestrial environments, aerobic methanotrophic bacteria are mainly responsible for oxidizing the methane. In marine sediments the coupling of the anaerobic oxidation of methane (AOM) with sulfate reduction, often by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria, was found to consume almost all the upward diffusing methane. Recently, we showed geochemical evidence for AOM driven by iron reduction in Lake Kinneret (LK) (Israel) deep sediments and suggested that this process can be an important global methane sink. The goal of the present study was to link the geochemical gradients found in the porewater (chemical and isotope profiles) with possible changes in microbial community structure. Specifically, we examined the possible shift in the microbial community in the deep iron-driven AOM zone and its similarity to known sulfate driven AOM populations. Screening of archaeal 16S rRNA gene sequences revealed Thaumarchaeota and Euryarchaeota as the dominant phyla in the sediment. Thaumarchaeota, which belongs to the family of copper containing membrane-bound monooxgenases, increased with depth while Euryarchaeota decreased. This may indicate the involvement of Thaumarchaeota, which were discovered to be ammonia oxidizers but whose activity could also be linked to methane, in AOM in the deep sediment. ANMEs sequences were not found in the clone libraries, suggesting that iron-driven AOM is not through sulfate. Bacterial 16S rRNA sequences displayed shifts in community diversity with depth. Proteobacteria and Chloroflexi increased with depth, which could be connected with their different dissimilatory anaerobic processes. The observed changes in microbial community structure suggest possible direct and indirect mechanisms for iron-driven AOM in deep sediments.
On the computation of planetary boundary layer height using the bulk Richardson number method
Authors: Zhang Y. , Gao Z. , Li D. , Li Y. , Zhang N. , Zhao X. , Chen J.
Published: June 2014

Abstract. Experimental data from four intensive field campaigns are used to explore the variability of the critical bulk Richardson number, which is a key parameter for calculating the planetary boundary layer height (PBLH) in numerical weather and climate models with the bulk Richardson method. First, the PBLHs of three different thermally-stratified boundary layers (i.e., strongly stable boundary layer, weakly stable boundary layer, and unstable boundary layer) from the four field campaigns are determined using the turbulence method, the potential temperature gradient method, the low-level jet method, or the modified parcel method. Then for each type of boundary layer, an optimal critical Richardson numbers is obtained through linear fitting and statistical error minimization methods so that the bulk Richardson method with this optimal critical bulk Richardson number yields similar estimates of PBLHs as the methods mentioned above. We find that the optimal critical bulk Richardson number increases as the atmosphere becomes more unstable: 0.24 for strongly stable boundary layer, 0.31 for weakly stable boundary layer, and 0.39 for unstable boundary layer. Compared with previous schemes that use a single value of critical bulk Richardson number for calculating the PBLH, the new values of critical bulk Richardson number that proposed by this study yield more accurate estimate of PBLH.
Quantifying the human impact on water resources: a critical review of the water footprint concept
Authors: Chenoweth J. , Hadjikakou M. , Zoumides C.
Published: June 2014

Abstract. The water footprint is a consumption-based indicator of water use, referring to the total volume of freshwater used directly and indirectly by a nation or a company, or in the provision of a product or service. Despite widespread enthusiasm for the development and use of water footprints, some concerns have been raised about the concept and its usefulness. A variety of methodologies have been developed for water footprinting which differ with respect to how they deal with different forms of water use. The result is water footprint estimates which vary dramatically, often creating confusion. Despite these methodological qualms, the concept has had notable success in raising awareness about water use in agricultural and industrial supply chains, by providing a previously unavailable and (seemingly) simple numerical indicator of water use. Nevertheless, and even though a range of uses have already been suggested for water footprinting, its policy value remains unclear. Unlike the carbon footprint which provides a universal measure of human impact on the atmosphere's limited absorptive capacity, the water footprint in its conventional form solely quantifies a single production input without any accounting of the impacts of use, which vary spatially and temporally. Following an extensive review of the literature related to water footprints, this paper critically examines the present uses of the concept, focusing on its current strengths, shortcomings and promising research avenues to advance it.
The suitability of remotely sensed soil moisture for improving operational flood forecasting
Authors: Wanders N. , Karssenberg D. , de Roo A. , de Jong S. M. , Bierkens M. F. P.
Published: June 2014

Abstract. We evaluate the added value of assimilated remotely sensed soil moisture for the European Flood Awareness System (EFAS) and its potential to improve the prediction of the timing and height of the flood peak and low flows. EFAS is an operational flood forecasting system for Europe and uses a distributed hydrological model (LISFLOOD) for flood predictions with lead times of up to 10 days. For this study, satellite-derived soil moisture from ASCAT (Advanced SCATterometer), AMSR-E (Advanced Microwave Scanning Radiometer - Earth Observing System) and SMOS (Soil Moisture and Ocean Salinity) is assimilated into the LISFLOOD model for the Upper Danube Basin and results are compared to assimilation of discharge observations only. To assimilate soil moisture and discharge data into the hydrological model, an ensemble Kalman filter (EnKF) is used. Information on the spatial (cross-) correlation of the errors in the satellite products, is included to ensure increased performance of the EnKF. For the validation, additional discharge observations not used in the EnKF are used as an independent validation data set. Our results show that the accuracy of flood forecasts is increased when more discharge observations are assimilated; the mean absolute error (MAE) of the ensemble mean is reduced by 35%. The additional inclusion of satellite data results in a further increase of the performance: forecasts of baseflows are better and the uncertainty in the overall discharge is reduced, shown by a 10% reduction in the MAE. In addition, floods are predicted with a higher accuracy and the continuous ranked probability score (CRPS) shows a performance increase of 5–10% on average, compared to assimilation of discharge only. When soil moisture data is used, the timing errors in the flood predictions are decreased especially for shorter lead times and imminent floods can be forecasted with more skill. The number of false flood alerts is reduced when more observational data is assimilated into the system. The added values of the satellite data is largest when these observations are assimilated in combination with distributed discharge observations. These results show the potential of remotely sensed soil moisture observations to improve near-real time flood forecasting in large catchments.