bluuebunny/crossref_metadata_2025 huggingface dataset:
The Tensile Properties of PVB at Intermediate Strain Rate Using the In Situ Hopkinson Bar
Authors: Li K. , Chen Rong , Zhang H. , Wen X.
Published: August 2015

Polyvinyl butyral (or PVB) is commonly used as interlayer in architectural laminated glass and windshield in automobiles for its strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. A modified in-situ Hopkinson bar system is used to measure the tensile properties of the PVB with the strain rates of 30~100 s-1. In this system, a high impedance striker tube with the rubber pulse shaper is use to generate a long loading pulse of 50ms. Two X-cut quartz piezoelectric force transducers are sandwiched between the specimen and two bars respectively to directly measure the dynamic loading forces, and the strain field of the specimen is calculated by the Digital Image Correlation (DIC) method via photos obtained by the high speed camera. The local deformation of the full-field specimen was clearly displayed and the fracture strain of the specimen was evaluated. The results show that the tensile strengths of the PVB increase with increasing loading strain rates.
Investigation of the Large Scale Borehole Soundless Cracking Experiment on the Concrete Members
Authors: Xu Quan Jun , Jiang Nan , Long Yuan , Liao Yu , Yang Tao , Ji Ran , Liu Di
Published: August 2015

In this paper, by the large scale borehole soundless cracking method, the fracture experiments were performed on the plain concrete and reinforced concrete. For plain concrete experiment, the open borehole was prefabricated in the concrete pillar at first. Secondly, two non-woven fabric bags contained soundless cracking agent were prepared, one for the main expanding and the other for blocking. Thirdly, the main expanding bag was plugged, and then the blocking bag. At last, the cracks in the concrete pillar were developed within 3 hours. For reinforced concrete experiment, the closed boreholes were prefabricated in the concrete beam. First the strain gauges were pasted on the designed locations of the stirrups. Secondly, the boreholes were filled with expanding grout and closed by the flange. The beam was cracked afterwards, and the strain was measured by the test system. It is proved that the large scale borehole soundless cracking method on the concrete members is practicable.
Experimental Study on the Constitutive Relation of SPHSC under Uniaxial Compression Loading
Authors: Zhou Hao , Huang Pei Yan , Guo Xin Yan , Zheng Xiao Hong
Published: August 2015

Steel fiber reinforced polymer high strength structural concrete (SPHSC) is a new composite material which is used in long-span bridge structures invented by this research team. Based on the new composite material, the experiments of stress-strain full curves under uniaxial compression were carried out. The stress-strain full curves were achieved from the simple improved method. By the method of theoretical derivation and experimental data fitting, the constitutive equation of SPHSC which contains only two undetermined parameters of compressive strength and parameter of steel fiber was obtained. The study is the theoretic basis of the new material which was widely use in civil engineering.
Validation of the Tabulated Johnson-Cook Model for a Dynamic Compression Simulation
Authors: Li Guo Ju , Fan Qun Bo , Gao Rui Hua , Liu Jin Tao , Miao Cheng
Published: August 2015

MAT224 is a tabulated version of the Johnson-Cook model in LS-DYNA. Compared with the original Johnson-Cook material, MAT224 was developed to simulate the dynamic response of a material by just defining the effective stress as a function of effective plastic strain at different strain rates and temperatures, thus avoiding the tedious parameter fitting procedures in the traditional Johnson-Cook model. However, the stability and precision of solution is strongly dependent on the effective stress versus effective strain curves in MAT224, and unreasonable curve data will lead to warnings or errors in the process of solution. In the current study, a two-dimensional axisymmetric finite element model for the Ti-6Al-4V titanium alloy under dynamic compression was built, and MAT224 was employed. By investigating the effects of the curve numbers, strain ranges, data points, as well as changing tendencies, on the simulation results, the stability and the reliability for MAT224 are systematically studied.
A Study on Very High Cycle Fatigue Properties of Low Flammability Magnesium Alloy in Rotating Bending and Axial Loading
Authors: Sakai Tatsuo , Kikuchi Shoichi , Nakamura Yuki , Ninomiya Noriyuki
Published: August 2015

In order to use a low flammability magnesium alloy as structural components, very high cycle fatigue properties of this alloy (AMCa602) were investigated. S-N properties obtained in both rotating bending and axial loading were compared with each other. It was found that S-N curve in the axial loading appeared a little lower than that in the rotating bending due to the differences of stress distributions and critical volumes for both loading types. Moreover, the statistical aspect on the fatigue property was analyzed as P-S-N characteristics in the rotating bending. After fatigue tests, fracture surfaces of failed specimens were observed by means of a scanning electron microscope (SEM) and the microstructures at the crack initiation site and the propagation path were also observed by combining FIB technique and EBSD analysis. Thus, it was found that some specimens failed from surface inclusions and their fatigue lives were lower in comparison to those of the specimens without surface inclusions. In addition, the fracture surfaces of this alloy revealed very rough in the usual life region, whereas a characteristic smooth area was observed on the fracture surfaces of specimens failed in the surface inclusion-initiated fracture and in very high cycle regime. A stress intensity factor range at the front of the smooth area (ΔKsmooth) tended to a definite value so that the fracture mechanism of this alloy was governed by a concept of ΔK.
Fabrication of Multi-Scale Grid Patterns as Deformation Carriers in Optical Methods
Authors: Wang Qing Hua , Ri Shi En , Tsuda Hiroshi , Kishimoto Satoshi , Tanaka Yoshihisa , Kagawa Yutaka
Published: August 2015

Multi-scale grid is an essential deformation carrier in optical methods for multi-scale deformation measurement. In this study, several new-type multi-scale grids were designed and fabricated by electron beam lithography. Each pattern includes several periodically distributed dots with the same spacing but different sizes. As a consequence, the grayscale of the whole grid pattern periodically changes. The peak parts of the grayscale generate a secondary grid, i.e., the large-scale grid. The ratio of the large-scale grid pitch to the small-scale grid pitch can be easily adjusted according to the requirement. The natural integration between the small-scale grid and the large-scale grid works well in eliminating the mutual disturbance between the different-scale grids. Besides, this type of grid has a very high success rate in fabrication owing to the small differences in size between the big dots and the small dots. The proposed multi-scale grid pattern is expected to serve as the deformation carrier in moiré methods and geometric phase analysis for multi-scale deformation measurement.
Numerical Simulation of Damage Effective of Explosion in Buildings
Authors: Xu Wen Long , Wang Cheng , Bi Yong , Gao Shu Ping
Published: August 2015

The software AUTODYN is used to investigate the damage mechanism of explosion in the brick and concrete buildings with different mass of charge in this paper. The results show that the mesh size of 5mm is very appropriate to study internal explosion; the maximum pressure area in the junction between roof and wall is broken up first and has the highest velocity, where is far from explosion source; the internal explosion damage in brick and concrete buildings appears in the boundaries between walls and roof.
Investigation of Mesh Dependency of Materials Fracture in the Finite Element Simulation of a Projectile Penetrating into a Target
Authors: Liu Jin Tao , Fan Qun Bo , Cai Hong Nian , Li Guo Ju
Published: August 2015

In finite element numerical simulation, the calculating results of geometrical models with different mesh density tend to have obvious differences, especially when material damage and fracture are considered. In order to study the mesh dependency of the finite element calculation, models of a projectile penetrating into the target with different mesh densities are constructed by using LS-DYNA. A nonlocal approach is investigated and the results without and with MAT_NONLOCAL are compared. It is found that the nonlocal model with a variable characteristic length parameter provides a relatively accurate and stable result, and the calculation cost can be reduced.
Experimental Measurement of Residual Stress on Thermal Spray Coatings with Moire Interferometry and Hole-Drilling Method
Authors: Zhu Jian Guo , Zhang Bao Ge
Published: August 2015

Residual stress is one of the important factors in thermally sprayed deposits which affects both processing and performances. In the present study, the hole-drilling method and moire interferometry were used to determine the residual stress of thermally sprayed coatings to overcome certain limitations of the strain rosette version of hole drilling. The methodology was established based on the elastic theory and finite element method. The residual displacement was measured by moire interferometry and the residual stress of the thermally sprayed coating was calculated. The results have demonstrated that moire interferometry for surface displacement caused by hole-drilling is high sensitive, reliable and stable.
Interior 3D-Strain Mapping in Opaque Materials Using Digital Volumetric Speckle Photography and X-Ray Micro Computer Tomography
Authors: Mao Ling Tao , Sun Qian Wen , Chiang Fu Pen
Published: August 2015

Developing a true 3D experimental stress analysis technique has been the holy grail of solid mechanics researchers since the genesis of the field. Combined the high-resolution x-ray computer tomography (Micro CT) with the 2D speckle photography technique developed by one of us (Chiang), we recently proposed a new 3D strain analysis technique called Digital Volumetric Speckle Photography (DVSP). The elements of DVSP technique are as follows. A reference volumetric image of the specimen is recorded by a Micro-CT scan and stored as a reference. Under load the deformed CT image of the specimen is also recorded. Both volume images are divided into subimages of certain voxel arrays. Each corresponding pair of the subimages are ‘compared’ via a two-step 3D Fourier Transform analysis. The result is a 3D map of displacement vectors representing the collective displacement experienced by all the speckles within the subset of voxels. Strain distribution of the entire specimen can then be calculated using appropriate displacement strain relations. Application of this technique to strain mapping of red sandstone and composite are presented.
Numerical Model Building and Optimization of Concrete Based on the CT Images and Digital Volumetric Speckle Photography
Authors: Liu Yong Liang , Sun Qian Wen , Mao Ling Tao , Gao Jie , Su Hai Cheng
Published: August 2015

In recent years, the research on the mesostructure of the concrete by using numerical simulation has been a hot topic. Mesoscopic research would contribute to reveal the concrete cracking failure mechanism. In this paper, the aggregate, the mortar , the interface and the pore are segmented based on CT images . With the aid of Mimics software, the numerical model for ANSYS is built. Besides this, the concrete specimen under uniaxial compression is scanned by using micro-CT in situ. The volumetric images under different loadings are acquired. By using digital volumetric speckle photography (DVSP) method, interior 3D deformation is obtained. Combined with the experiment results, the numerical model is optimized. Based on the optimized model, mesoscopic mechanics of concrete is analyzed by using numerical simulation.
Study on Preparation and Mechanical Properties of W-Cu Alloy with Low W-W Contiguity
Authors: Hu Zhi Yu , Liu Jin Xu , Li Shu Kui , Zou Qing He , Wang Xing
Published: August 2015

Electroless copper plating method combined with spark plasma sintering (SPS) was used to fabricate W-Cu alloy with low W-W contiguity. Results show that W-Cu alloy with low W-W contiguity and high relative density can be obtained by this method. With sintering temperature increased from 860°C to 1060°C, the relative density of W-Cu alloy shows a rapidly increasing tendency, but the W-W contiguity keeps at a low level. Compression testing results show that the ductility of prepared W-Cu alloy is sensitive to strain rate, and the failure strain of the W-Cu alloy shows obviously increasing tendency with the loading strain rate increased from 10-3 to 103.
Effects of Silica Nanoparticle Addition on Dynamic Properties of Poly(lactic acid)
Authors: Nishida Masahiro , Takeuchi Yuma , Natsume Rie , Fukuda Norio , Ito Hiroaki
Published: August 2015

Bioplastics are plastics derived from renewable sources such as corn starch or microbe and biodegradable plastics are plastics that are capable of being decomposed by bacteria or other living organisms. Poly (lactic acid) (PLA) is a typical and biodegradable bioplastic. It has been recognized as a promising alternative material for petroleum-based polymers. In order to increase Young’s modulus, in the present study, silica nanoparticles were added to PLA. The effects of the addition of silica nanoparticles and the surface treatment of nanosilica particles on dynamic properties of nanoparticle added PLA were examined using tensile split Hopkinson pressure bar method and the Izod impact strength tests.
Aerodynamic Interaction between Rotor and Tilting Wing in Hovering Flight Condition
Authors: Droandi Giovanni , Zanotti Alex , Gibertini Giuseppe
Published: August 2015

The hovering performance and the lifting capability of tiltrotor aircraft are strongly affected by the aerodynamic interaction between wing and rotors. The tiltwing concept represents an interesting technology to increase the hover performance by reducing the wing–rotor interference.
The present work investigates the aerodynamic interaction between wing and rotor in hover for a scaled tiltwing aircraft half-span model. A comprehensive experimental campaign, including force measurements and particle image velocimetry surveys, was performed together with computational fluid
dynamics simulations. Numerical predictions were validated using experimental data and were used to describe the flow field.
Minor and trace element distribution in the heavy minerals of the rivers and streams of the Keno Hill District, Yukon Territory
Authors: Gleeson C F , Boyle R W
Published: August 2015

The distribution of selected elements in heavy minerals from the drainage systems of the Keno Hill district, Yukon is described. Most of the known mineral deposits of the district are reflected by higher than average contents of one or more elements in the heavy
mineral fractions, and a number of anomalous sites in streams in the drainage net were found that merit further investigation. The conclusion is drawn that low density reconnaissance stream sediment surveys involving geochemical analyses of heavy mineral concentrates is an effective way of outlining
mineralized areas. In the mountainous regions of Yukon elemental dispersion in the drainage systems is due as much to transport of particulate matter as to hydrologic processes. Traditionally heavy mineral surveys have been used to define areas enriched in metals having a low degree of chemical
mobility in the supergene cycle. The present study indicates, however, that analyses of heavy mineral concentrates for the chemically more mobile elements can outline metalliferous areas. In this respect geochemical and mineralogical analyses of heavy mineral concentrates from the drainage net can
complement normal stream sediment surveys and provide additional information that can aid in the interpretation of the stream sediment data. Finally, it is notable that particulate dispersion trains of hypogene and supergene minerals may be more extensive than hydromorphic trains especially in
carbonate terranes where the chemical mobility of some elements may be restricted due to the high pH.
Development, Evaluation and Implementation of Chief Complaint Groupings to Activate Data Collection
Authors: Bajaj L. , Hoffman J. , Alessandrini E. , Ballard D. W. , Norris R. , Tzimenatos L. , Swietlik M. , Tham E. , Grundmeier R. W. , Kuppermann N. , Dayan P. S. , Deakyne S. J. ,   the Pediatric Emergency Care Applied Research Network (PECARN)
Published: August 2015

Background: Overuse of cranial computed tomography scans in children with blunt head trauma unnecessarily exposes them to radiation. The Pediatric Emergency Care Applied Research Network (PECARN) blunt head trauma prediction rules identify children who do not require a computed tomography scan. Electronic health record (EHR) based clinical decision support (CDS) may effectively implement these rules but must only be provided for appropriate patients in order to minimize excessive alerts.

Objective: To develop, implement and evaluate site-specific groupings of chief complaints (CC) that accurately identify children with head trauma, in order to activate data collection in an EHR.

Methods: As part of a 13 site clinical trial comparing cranial computed tomography use before and after implementation of CDS, four PECARN sites centrally developed and locally implemented CC groupings to trigger a clinical trial alert (CTA) to facilitate the completion of an emergency department head trauma data collection template. We tested and chose CC groupings to attain high sensitivity while maintaining at least moderate specificity.

Results: Due to variability in CCs available, identical groupings across sites were not possible. We noted substantial variability in the sensitivity and specificity of seemingly similar CC groupings between sites. The implemented CC groupings had sensitivities greater than 90% with specificities between 75–89%. During the trial, formal testing and provider feedback led to tailoring of the CC groupings at some sites.

Conclusion: CC groupings can be successfully developed and implemented across multiple sites to accurately identify patients who should have a CTA triggered to facilitate EHR data collection. However, CC groupings will necessarily vary in order to attain high sensitivity and moderate-to-high specificity. In future trials, the balance between sensitivity and specificity should be considered based on the nature of the clinical condition, including prevalence and morbidity, in addition to the goals of the intervention being considered.

Citation: Deakyne SJ, Bajaj L, Hoffmann J, Alessandrini E, Ballard DW, Norris R, Tzimenatos L, Swietlik M, Tham E, Grundmeier RW, Kuppermann N, Dayan PS. Development, Evaluation and Implementation of Chief Complaint Groupings to Activate Data Collection in a Multi-Center Study of Clinical Decision Support for Children with Head Trauma. Appl Clin Inform 2015; 6: 521–535

http://dx.doi.org/10.4338/ACI-2015-02-RA-0019
Contribution from biogenic organic compounds to particle growth during the 2010 BEACHON-ROCS campaign in a Colorado temperate needleleaf forest
Authors: Zhou L. , Gierens R. , Sogachev A. , Mogensen D. , Ortega J. , Smith J. N. , Harley P. C. , Prenni A. J. , Levin E. J. T. , Turnipseed A. , Rusanen A. , Smolander S. , Guenther A. B. , Kulmala M. , Karl T. , Boy M.
Published: August 2015

Abstract. New particle formation (NPF) is an important atmospheric phenomenon. During an NPF event, particles first form by nucleation and then grow further in size. The growth step is crucial because it controls the number of particles that can become cloud condensation nuclei. Among various physical and chemical processes contributing to particle growth, condensation by organic vapors has been suggested as important. In order to better understand the influence of biogenic emissions on particle growth, we carried out modeling studies of NPF events during the BEACHON-ROCS (Bio–hydro–atmosphere interactions of Energy, Aerosol, Carbon, H2O, Organics & Nitrogen – Rocky Mountain Organic Carbon Study) campaign at Manitou Experimental Forest Observatory in Colorado, USA. The site is representative of the semi-arid western USA. With the latest Criegee intermediate reaction rates implemented in the chemistry scheme, the model underestimates sulfuric acid concentration by 50 %, suggesting either missing sources of atmospheric sulfuric acid or an overestimated sink term. The results emphasize the contribution from biogenic volatile organic compound emissions to particle growth by demonstrating the effects of the oxidation products of monoterpenes and 2-Methyl-3-buten-2-ol (MBO). Monoterpene oxidation products are shown to influence the nighttime particle loadings significantly, while their concentrations are insufficient to grow the particles during the day. The growth of ultrafine particles in the daytime appears to be closely related to the OH oxidation products of MBO.
Carbonyl sulfide exchange in soils for better estimates of ecosystem carbon uptake
Authors: Whelan M. E. , Hilton T. W. , Berry J. A. , Berkelhammer M. , Desai A. R. , Campbell J. E.
Published: August 2015

Abstract. Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil-COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soil COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from 5 new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois, > 800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. While COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.
Instantaneous longwave radiative impact of ozone: an application on IASI/MetOp observations
Authors: Doniki S. , Hurtmans D. , Clarisse L. , Clerbaux C. , Worden H. M. , Bowman K. W. , Coheur P.-F.
Published: August 2015

Abstract. Ozone is an important greenhouse gas in terms of anthropogenic radiative forcing (RF). RF calculations for ozone were until recently entirely model based and significant discrepancies were reported due to different model characteristics. However, new instantaneous radiative kernels (IRKs) calculated from hyperspectral thermal IR satellites have been able to help adjudicate between different climate model RF calculations. IRKs are defined as the sensitivity of the outgoing longwave radiation (OLR) flux with respect to the ozone vertical distribution in the full 9.6 μm band. Previous methods applied to measurements from the Tropospheric Emission Spectrometer (TES) on Aura, rely on an anisotropy approximation for the angular integration. In this paper, we present a more accurate but more computationally expensive method to calculate these kernels. The method of direct integration is based on similar principles with the anisotropy approximation, but deals more precisely with the integration of the Jacobians. We describe both methods and highlight their differences with respect to the IRKs and the ozone longwave radiative effect (LWRE), i.e. the radiative impact in OLR due to absorption by ozone, for both tropospheric and total columns, from measurements of the Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp-A. Biases between the two methods vary from −25 to +20 % for the LWRE, depending on the viewing angle. These biases point to the inadequacy of the anisotropy method, especially at nadir, suggesting that the TES derived LWRE are biased low by around 25 % and that chemistry-climate model OLR biases with respect to TES are underestimated. In this paper we also exploit the sampling performance of IASI to obtain first daily global distributions of the LWRE, for 12 days (the 15th of each month) in 2011, calculated with the direct integration method. We show that the temporal variation of global and latitudinal averages of the LWRE shows patterns which are controlled by changes in the surface temperature and ozone variation due to specific processes, such as the ozone hole in the Polar regions and stratospheric intrusions into the troposphere.
Spring and summer contrast in new particle formation over nine forest areas in North America
Authors: Yu F. , Luo G. , Pryor S. C. , Pillai P. R. , Lee S. H. , Ortega J. , Schwab J. J. , Hallar A. G. , Leaitch W. R. , Aneja V. P. , Smith J. N. , Walker J. T. , Hogrefe O. , Demerjian K. L.
Published: August 2015

Abstract. Recent laboratory chamber studies indicate a significant role for highly oxidized low volatility organics in new particle formation (NPF) but the actual role of these highly oxidized low volatility organics in atmospheric NPF remains uncertain. Here, particle size distributions (PSDs) measured in nine forest areas in North America are used to characterize the occurrence and intensity of NPF and to evaluate model simulations using an empirical formulation in which formation rate is a function of the concentrations of sulfuric acid and low volatility organics from alpha-pinene oxidation (Nucl-Org), and using an ion-mediated nucleation mechanism (excluding organics; Nucl-IMN). On average, NPF occurred on ~ 70 % of days during March for the four forest sites with springtime PSD measurements, while NPF occurred on only ~ 10 % of days in July for all nine forest sites. Both Nucl-Org and Nucl-IMN schemes capture the observed high frequency of NPF in spring, but the Nucl-Org scheme significantly over-predicts while the Nucl-IMN scheme slightly under-predicts NPF and particle number concentrations in summer. Statistical analyses of observed and simulated ultrafine particle number concentrations and frequency of NPF events indicate that the scheme without organics agrees better overall with observations. The two schemes predict quite different nucleation rates (including their spatial patterns), concentrations of cloud condensation nuclei, and aerosol first indirect radiative forcing in North America, highlighting the need to reduce NPF uncertainties in regional and global earth system models.
Vertical partitioning and controlling factors of gradient-based soil carbon dioxide fluxes in two contrasted soil profiles along a loamy hillslope
Authors: Wiaux F. , Vanclooster M. , Van Oost K.
Published: August 2015

Abstract. In this study we aim to elucidate the role of physical conditions and gas transfer mechanism along soil profiles in the decomposition and storage of soil organic carbon (OC) in subsoil layers. We use a qualitative approach showing the temporal evolution and the vertical profile description of CO2 fluxes and abiotic variables. We assessed soil CO2 fluxes throughout two contrasted soil profiles (i.e. summit and footslope positions) along a hillslope in the central loess belt of Belgium. We measured the time series of soil temperature, soil moisture and CO2 concentration at different depths in the soil profiles for two periods of 6 months. We then calculated the CO2 flux at different depths using Fick's diffusion law and horizon specific diffusivity coefficients. The calculated fluxes allowed assessing the contribution of different soil layers to surface CO2 fluxes. We constrained the soil gas diffusivity coefficients using direct observations of soil surface CO2 fluxes from chamber-based measurements and obtained a good prediction power of soil surface CO2 fluxes with an R2 of 92 %. We observed that the temporal evolution of soil CO2 emissions at the summit position is mainly controlled by temperature. In contrast, at the footslope, we found that long periods of CO2 accumulation in the subsoil alternates with short peaks of important CO2 release. This was related to the high water filled pore space that limits the transfer of CO2 along the soil profile at this slope position. Furthermore, the results show that approximately 90 to 95 % of the surface CO2 fluxes originate from the first 10 cm of the soil profile at the footslope. This indicates that soil OC in this depositional context can be stabilized at depth, i.e. below 10 cm. This study highlights the need to consider soil physical properties and their dynamics when assessing and modeling soil CO2 emissions. Finally, changes in the physical environment of depositional soils (e.g. longer dry periods) may affect the long-term stability of the large stock of easily decomposable OC that is currently stored in these environments.
Hydrologic controls on DOC, As and Pb export from a polluted peatland – the importance of heavy rain events, antecedent moisture conditions and hydrological connectivity
Authors: Broder T. , Biester H.
Published: August 2015

Abstract. Bogs can store large amounts of lead (Pb) and arsenic (As) from atmospheric deposition of anthropogenic emissions. Pb and As are exported along with dissolved organic carbon (DOC) from these organic-rich systems, but it is not yet clear which hydrological (pre)conditions favor their export. This study combines a 1-year monitoring of precipitation, bog water level and pore water concentration changes with bog discharge and DOC, iron, As and Pb stream concentrations. From these data, annual DOC, As, and Pb exports were calculated. Concentrations ranged from 5 to 30 mg L−1 for DOC, 0.2 to 1.9 μg L−1 for As, and 1.3 to 12 μg L−1 for Pb, with highest concentrations in late summer. As and Pb concentrations significantly correlated with DOC concentrations. Fluxes depended strongly on discharge, as 40 % of As and 43 % of Pb were exported during 10 % of the time with the highest discharge, pointing out the over-proportional contribution of short-time, high-discharge events to annual As, Pb and DOC export. Exponential increase in element export from the bog is explained by connection of additional DOC, As and Pb pools in the acrotelm during water table rise, which is most pronounced after drought. Pb, As and DOC concentrations in pore water provide evidence of an increase in the soluble Pb pool as soon as the peat layer becomes hydrologically connected, while DOC and As peak concentrations in runoff lag behind in comparison to Pb. Our data indicate a distinct bog-specific discharge threshold of 8 L s−1, which is thought to depend mainly on the bogs size and drainage conditions. Above this threshold, element concentrations do not further increase and discharge becomes diluted. Combining pore water and discharge data shows that As and Pb exports are dependent on not only the amount of precipitation and discharge but also on the frequency and depth of water table fluctuations. Comparing the annual bog As and Pb export with element inventories indicates that As is much more mobilized than Pb, with annual fluxes accounting for 0.85 and 0.27 ‰ of total As and Pb inventory, respectively.
Covariation of metabolic rates and cell size in coccolithophores
Authors: Aloisi G.
Published: August 2015

Abstract. Coccolithophores are sensitive recorders of environmental change. The size of their coccosphere varies in the ocean along gradients of environmental conditions and provides a key for understanding the fate of this important phytoplankton group in the future ocean. But interpreting field changes in coccosphere size in terms of laboratory observations is hard, mainly because the marine signal reflects the response of multiple morphotypes to changes in a combination of environmental variables. In this paper I examine the large corpus of published laboratory experiments with coccolithophores looking for relations between environmental conditions, metabolic rates and cell size (a proxy for coccosphere size). I show that growth, photosynthesis and, to a lesser extent, calcification covary with cell size when pCO2, irradiance, temperature, nitrate, phosphate and iron conditions change. With the exception of phosphate and temperature, a change from limiting to non-limiting conditions always results in an increase in cell size. An increase in phosphate or temperature (below the optimum temperature for growth) produces the opposite effect. The magnitude of the coccosphere-size changes observed in the laboratory is comparable to that observed in the ocean. If the biological reasons behind the environment–metabolism–size link are understood, it will be possible to use coccosphere-size changes in the modern ocean and in marine sediments to investigate the fate of coccolithophores in the future ocean. This reasoning can be extended to the size of coccoliths if, as recent experiments are starting to show, coccolith size reacts to environmental change proportionally to coccosphere size. The coccolithophore database is strongly biased in favour of experiments with the coccolithophore Emiliania huxleyi (E. huxleyi; 82 % of database entries), and more experiments with other species are needed to understand whether these observations can be extended to coccolithophores in general. I introduce a simple model that simulates the growth rate and the size of cells forced by nitrate and phosphate concentrations. By considering a simple rule that allocates the energy flow from nutrient acquisition to cell structure (biomass) and cell maturity (biological complexity, eventually leading to cell division), the model is able to reproduce the covariation of growth rate and cell size observed in laboratory experiments with E. huxleyi when these nutrients become limiting. These results support ongoing efforts to interpret coccosphere and coccolith size measurements in the context of climate change.
N2O fluxes from the littoral zone of a Chinese reservoir
Authors: Yang M. , Geng X. M. , Grace J. , Jia Y. F. , Liu Y. Z. , Jiao S. W. , Shi L. L. , Lu C. , Zhou Y. , Lei G. C.
Published: August 2015

Abstract. There have been few studies of greenhouse gas emissions from reservoirs, despite the remarkable growth in the number of reservoirs in developing countries. We report a case study that focuses on the littoral zone of a major Chinese reservoir, where we established measurements of N2O fluxes using the static chamber technique at five different water levels (deep water, shallow water, seasonally flooded, control for seasonally flooded, and non-flooded). The "control for seasonal flooded" had similar vegetation to the "seasonally flooded" but was not actually flooded as it was on a higher piece of land. Seasonal, diurnal and spatial variations of N2O flux and environmental factors were monitored throughout the growing season which included a flood event during summer rains. The N2O flux ranged from −136.6 to 381.8 μg m−2 h−1 averaging 6.8 μg m−2 h−1. Seasonal and spatial variation was significant but diurnal variation was not. Non-flooded dry land emitted more N2O than flooded land, no matter whether it was permanently or seasonally flooded. Piecewise correlation was found between N2O flux, air temperature and soil nitrate concentration. Positive correlation was shown between N2O flux and dissolved oxygen in water. There were significantly higher emissions from farmland. We compared these results with our recently published study of CH4 emissions, carried out simultaneously at the same site as those in the present study. Completely different patterns between the two gases are demonstrated. We conclude that the littoral zone is a hotspot for N2O emissions in the summer, especially when the shores of the lake are used for the farming of maize. But in terms of the overall greenhouse gas budget, the fluxes of N2O are not as important as those of CH4.
Intact polar lipids of Thaumarchaeota and anammox bacteria as indicators of N cycling in the eastern tropical North Pacific oxygen-deficient zone
Authors: Sollai M. , Hopmans E. C. , Schouten S. , Keil R. G. , Sinninghe Damsté J. S.
Published: August 2015

Abstract. In the last decade our understanding of the marine nitrogen cycle has improved considerably thanks to the discovery of two novel groups of microorganisms: ammonia-oxidizing archaea (AOA) and anaerobic ammonia-oxidizing (anammox) bacteria. Both groups are important in oxygen-deficient zones (ODZs), where they substantially affect the marine N budget. These two groups of microbes are also well known for producing specific membrane lipids, which can be used as biomarkers to trace their presence in the environment. We investigated the occurrence and distribution of AOA and anammox bacteria in the water column of the eastern tropical North Pacific (ETNP) ODZ, one of the most prominent ODZs worldwide. Suspended particulate matter (SPM) was collected at different depths of the water column in high resolution, at both a coastal and an open-ocean setting. The SPM was analyzed for AOA- and anammox bacteria-specific intact polar lipids (IPLs), i.e., hexose-phosphohexose (HPH)-crenarchaeol and phosphatidylcholine (PC)-monoether ladderane. Comparison with oxygen profiles reveals that both the microbial groups are able to thrive at low (< 1 μM) concentrations of oxygen. Our results indicate a clear niche segregation of AOA and anammox bacteria in the coastal waters of the ETNP but a partial overlap of the two niches of these microbial species in the open-water setting. The latter distribution suggests the potential for an interaction between the two microbial groups at the open-ocean site, although the nature of this hypothetical interaction (i.e., either competition or cooperation) remains unclear.
Effects of dust additions on phytoplankton growth and DMS production in high CO2 northeast Pacific HNLC waters
Authors: Mélançon J. , Levasseur M. , Lizotte M. , Scarratt M. , Tremblay J.-É. , Tortell P. , Yang G.-P. , Shi G.-Y. , Gao H.-W. , Semeniuk D. M. , Robert M. , Arychuk M. , Johnson K. , Sutherland N. , Davelaar M. , Nemcek N. , Peña A. , Richardson W.
Published: August 2015

Abstract. Ocean acidification (OA) is likely to have an effect on the fertilizing potential of desert dust in high-nutrient, low-chlorophyll oceanic regions, either by modifying Fe speciation and bioavailability, or by altering phytoplankton Fe requirements and acquisition. To address this issue, short incubations (4 days) of northeast subarctic Pacific waters enriched with either FeSO4 or dust, and set at pH 8.0 (in situ) and 7.8 were conducted in August 2010. We assessed the impact of a decrease in pH on dissolved Fe concentration, phytoplankton biomass, taxonomy and productivity, and the production of dimethylsulfide (DMS) and its algal precursor dimethylsulfoniopropionate (DMSP). Chlorophyll a (chl a) remained unchanged in the controls and doubled in both the FeSO4-enriched and dust-enriched incubations, confirming the Fe-limited status of the plankton assemblage during the experiment. In the acidified treatments, a significant reduction (by 16–38 %) of the final concentration of chl a was measured compared to their non-acidified counterparts, and a 15 % reduction in particulate organic carbon (POC) concentration was measured in the dust-enriched acidified treatment compared to the dust-enriched non-acidified treatment. FeSO4 and dust additions had a fertilizing effect mainly on diatoms and cyanobacteria. Lowering the pH affected mostly the haptophytes, but pelagophyte concentrations were also reduced in some acidified treatments. Acidification did not significantly alter DMSP and DMS concentrations. These results show that dust deposition events in a low-pH iron-limited Northeast subarctic Pacific are likely to stimulate phytoplankton growth to a lesser extent than in today's ocean during the few days following fertilization and point to a low initial sensitivity of the DMSP and DMS dynamics to OA.
A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 1816
Authors: Brugnara Y. , Auchmann R. , Brönnimann S. , Allan R. J. , Auer I. , Barriendos M. , Bergström H. , Bhend J. , Brázdil R. , Compo G. P. , Cornes R. C. , Dominguez-Castro F. , van Engelen A. F. V. , Filipiak J. , Holopainen J. , Jourdain S. , Kunz M. , Luterbacher J. , Maugeri M. , Mercalli L. , Moberg A. , Mock C. J. , Pichard G. , Řezníčková L. , van der Schrier G. , Slonosky V. , Ustrnul Z. , Valente M. A. , Wypych A. , Yin X.
Published: August 2015

Abstract. The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815–1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.
Analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer
Authors: Huang C.-S. , Chen J.-J. , Yeh H.-D.
Published: August 2015

Abstract. This study develops a three-dimensional mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. The head solution for the point sink is derived by applying the methods of double-integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.
Artificial neural networks and multiple linear regression model using principal components to estimate rainfall over South America
Authors: dos Santos T. S. , Mendes D. , Torres R. R.
Published: August 2015

Abstract. Several studies have been devoted to dynamic and statistical downscaling for analysis of both climate variability and climate change. This paper introduces an application of artificial neural networks (ANN) and multiple linear regression (MLR) by principal components to estimate rainfall in South America. This method is proposed for downscaling monthly precipitation time series over South America for three regions: the Amazon, Northeastern Brazil and the La Plata Basin, which is one of the regions of the planet that will be most affected by the climate change projected for the end of the 21st century. The downscaling models were developed and validated using CMIP5 model out- put and observed monthly precipitation. We used GCMs experiments for the 20th century (RCP Historical; 1970–1999) and two scenarios (RCP 2.6 and 8.5; 2070–2100). The model test results indicate that the ANN significantly outperforms the MLR downscaling of monthly precipitation variability.
Dynamic evaluation of ecosystem service value of the riparian zone based on remote sensing from 1986 to 2012
Authors: Fu B. L. , Li Y. , Zhang B. , Yin B. S. , Zhu H. L. , Xing Z. F.
Published: August 2015

Abstract. In this paper, we calculated comparable and dynamic ecosystem service value per unit area in the riparian zone of Second Songhua River; then we also estimated changes in the value of ecosystem services resulting from land use changes; finally, we continuously evaluated the riparian ecosystem service value based on 520 basic evaluation units (BEUs) and explored the trend of the riparian ecosystem service value from 1986 to 2012. The results indicated that comparable economic values of per unit area food production of farmland ecosystems in 2012 almost increased three times more than that in 1986 from 154.83 to 382.45 $ ha−1; the people's willingness to pay for farmland ecosystem services increased from 0.24 in 1986 to 0.48 in 2012; the land areas supporting the environment and society generally declined, whereas areas of farmland significantly increased from 1986 to 2012; the riparian total ecosystem service value increased from 42.30 million $ in 1986 to 119.67 million $ in 2012, with an average increase rate of 4.06 % yr−1; the ecosystem service value of four reaches all have seen a sharp increase from 1986 to 2012; the average ecosystem service value of a reach was the smallest one in the four reaches, and the value of c and d reach was significantly more than other two reaches.