bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Progress of Crystal Growth Technology for Multi-Crystalline Silicon Solar Ingot
Authors: Lan C.W. , Yang Y.M. , Yu A. , Wu Y.C. , Hsu B. , Hsu Chuck Wen Ching , Yang A.
Published: October 2015

In recent years, silicon solar cells continue to remain the main stream in photovoltaic (PV) industry, particularly of made from multi-crystalline silicon (mc-Si). The progress of crystal growth technology for mc-Si ingot using directional solidification (DS) is particularly significant. With the breakthrough of the so-called high-performance (HP) mc-Si technology in 2011, the mc-Si solar cell efficiency had increased from 16.6% in 2011 to 18 % or beyond in 2013. Nowadays, HP mc-Si, solar cells from a normal screen-printing aluminum back surface field (Al-BSF) production line could easily reach 18.3%. With the passivated emitter and rear cell (PERC) structure using PECVDalumina passivation, an average efficiency of over 19.2% could also be obtained. The emerging of HP mc-Si almost blocked the development of mono-like technology in 2012, and pushed p-type mono-Si cells to higher efficiency by using advanced technology. Unlike the conventional way of having large grains and electrically-inactive twin boundaries, the growth of HP mc-Si is from small and uniform grains having more random GBs. The grains developed from such grain structures significantly relaxes the thermal stress and suppresses the massive generation and propagation of dislocation clusters. Currently, most of commercial mc-Si ingots are grown by this concept, which could be implemented by seeded with small silicon particles or using nucleation agent coatings. The seeded growth has been well adopted in industry. However, the melting control of the seed layer and the thick red zone induced remain key issues in mass production. Several methods have been considered to resolve these issues with some success. The use of nucleation agent layers is a simpler approach, but the control of initial grain structures remains challenging.
Enhanced Internal Gettering of Iron in n/n+ Epitaxial Silicon Wafer: Effect of High Temperature Rapid Thermal Annealing in Nitrogen Ambient
Authors: Dong Peng , Liang Xing Bo , Tian Da Xi , Ma Xiang Yang , Yang De Ren
Published: October 2015

We report a strategy feasible for improving the internal gettering (IG) capability of iron (Fe) for n/n+ epitaxial silicon wafers using the heavily arsenic (As)-doped Czochralski (CZ) silicon wafers as the substrates. The n/n+ epitaxial silicon wafers were subjected to the two-step anneal of 650 °C/16 h + 1000 °C/16 h following the rapid thermal processing (RTP) at 1250 °C in argon (Ar) or nitrogen (N2) atmosphere. It is found that the prior RTP in N2 atmosphere exhibits much stronger enhancement effect on oxygen precipitation (OP) in the substrates than that in Ar atmosphere, thereby leading to a better IG capability of Fe contamination on the epitaxial wafer. In comparison with the RTP in Ar atmosphere, the one in N2 atmosphere injects not only vacancies but also nitrogen atoms of high concentration into the heavily As-doped silicon substrate. The co-action of vacancy and nitrogen leads to the enhanced OP in the substrate and therefore the better IG capability for the n/n+ epitaxial silicon wafer.
Segregation Gettering Model for Nickel in p/p+ Silicon Wafers
Authors: Torigoe Kazuhisa , Ono Toshiaki , Nakamura Kozo
Published: October 2015

The segregation gettering of nickel in p/p+ silicon epitaxial wafers is analyzed based on the gettering model considering the competitive interaction between segregation effect and nickel precipitations at the surface during the cooling process after heat treatments. It is found that the segregation is effective at higher temperatures than Ni-silicide formation temperatures even if the nickel donor level lies close to the valence band edge, resulting in the suppression of Ni-silicide formation at lower temperatures. The gettering effect is suggested to be useful for the low temperature process for a future device fabrication.
Modeling the Post-Implantation Annealing of Platinum
Authors: Badr Elie , Pichler Peter , Schmidt Gerhard
Published: October 2015

Platinum in silicon is conveniently used for lifetime engineering in power devices. Its deep energy level ensures an efficient recombination of charge carriers while it is sufficiently far away from mid bandgap to be a low generation center. Contemporary development aims at replacing diffusion from platinum silicide by implantation. To obtain a better understanding of the mechanisms involved, a series of experiments has been performed in this work and interpreted by numerical simulation.
Electrical Levels and Diffusion Barriers of Early 3d and 4d Transition Metals in Silicon
Authors: Marinopoulos A.G. , Santos P. , Coutinho J.
Published: October 2015

Early transition metals (TMs) of the 3d and 4d rows are undesired contaminants in solarandelectronic-grade Si. From the theoretical standpoint, understanding the properties of these TMs insilicon still remains a challenging problem owing to the strong correlations among the TM d-electrons.The present study proposes a first-principles Hubbard-corrected DFT+U approach, with on-site parametersaccounting separately for electron Coulomb (U) and exchange (J) effects. We use this approachtogether with conventional DFT to determine electrical levels and migration barriers of early3d (Ti, V and Cr) and 4d (Zr, Nb and Mo) TMs in Si. Comparisons with experimental data allowedus to uniquely assign the deep levels in the gap appraising also the effect of on-site correlation. Ourresults also resolve existing controversies in the literature concerning the type and origin of the donorlevels of Cr and Mo. For all the metals, with the exception of Cr, high barriers of interstitial diffusionare obtained, thus confirming that most of these TMs are slow diffusers in silicon.
Effect of Nitrogen-Doping on the Properties of Radiation Defect Centers in FZ Silicon
Authors: Kamiński P. , Kozłowski R. , Surma Barbara , Kozubal Michal , Hindrichsen Christian , Sveigaard Theis , Jensen Leif , Kwestarz Michal , Jabłoński J.
Published: October 2015

High-resolution photoinduced transient spectroscopy (HRPITS) has been applied to determining the properties and concentrations of radiation defect centers formed in FZ silicon single crystals subjected to doping with phosphorus in neutron transmutation processes. The studies were performed immediately after the neutron irradiation on the samples with the resistivity of the order of 105 Ωcm. The preset target resistivity was around 2000 Ωcm. The N-doping effect on the material radiation damage has been demonstrated. It is shown that in the N-enriched material, the radiation defect centers with activation energies of 81, 125, 160, 185, and 390 meV are not observed and the concentrations of the defect centers with activation energies of 46, 84, 133, 140, 265, 300, 380, 460, and 546 meV are significantly lower than those in the N-free material. We also show that the majority of defect centers produced by the irradiation of FZ silicon with fast neutrons are also observed after neutron transmutation doping.
Interaction of Interstitial Copper with Isolated Vacancies in Silicon
Authors: Yarykin Nikolai , Weber Jörg
Published: October 2015

The spectrum of defects produced by 5 MeV electron irradiation in oxygen-lean p-type silicon strongly contaminated with interstitial copper (Cui) is studied using the deep-level transient spectroscopy. It is observed that the room-temperature irradiation creates a large amount of CuPL centers (complexes including one substitutional and three interstitial Cu atoms). The analysis shows that this process is govern by formation of the substitutional copper atoms due to the direct reaction between irradiation-induced vacancies and mobile Cui species. This reaction consumes nearly all irradiation-induced vacancies and affects strongly the standard spectrum of radiation defects.
Reduced Thermal Conductivity in Silicon Thin-Films via Vacancies
Authors: Wight Neil M. , Bennett Nick S.
Published: October 2015

An experimental method is defined that reduces the thermal conductivity in Si films by ~90 % compared to control samples, while keeping the thermoelectric power factor almost unchanged. This is done by creating vacancy-rich films via high-energy self-implantation of Si, followed by rapid-thermal annealing. TCAD simulations suggest that this approach is scalable for application in thin-film thermoelectric generators, as an alternative to more expensive and less Earth-abundant materials such as bismuth telluride. This approach to Si thermoelectrics could be straight-forward for scale-up to thin-film device dimensions, something that is a major challenge for other methods used for Si thermal conductivity reduction.
A Nanoscale Adventure with Silicon: Synthesis, Surface Chemistry, and other Surprises
Authors: Mobarok Md Hosnay , Purkait Tapas K. , Veinot Jonathan G.C.
Published: October 2015

The preparation and surface chemistry Si quantum dots (SiQDs) are currently an intense focus of research because of their size dependent optical properties and many potential applications. SiQDs offer several advantages over other quantum dots; Si is earth abundant, non-toxic and biocompatible. This account briefly highlights recent advancements made by our research group related to the synthesis, functionalization, surface dependent optical properties and applications of SiQDs.
Misfit Dislocation Free Epitaxial Growth of SiGe on Compliant Nano-Structured Silicon
Authors: Zaumseil Peter , Schubert Markus Andreas , Yamamoto Yuji , Skibitzki Oliver , Capellini Giovanni , Schroeder Thomas
Published: October 2015

The integration of germanium (Ge) into silicon-based microelectronics technologies is currently attracting increasing interest and research effort. One way to realize this without threading and misfit dislocations is the so-called nanoheteroepitaxy approach. We demonstrate that a modified Si nanostructure approach with nanopillars or bars separated by TEOS SiO2 can be used successfully to deposit SiGe dots and lines free of misfit dislocations. It was found that strain relaxation in the pseudomorphically grown SiGe happens fully elastically. These studies are important for the understanding of the behavior of nanostructured Si for the final goal of Ge integration via SiGe buffer.
Influence of Composition of Aqueous Electrolytes on Anisotropy of Porous Layer Formation Rate in Heavily Doped Silicon
Authors: Zharova Yuliya A.
Published: October 2015

Concentration dependence of the pore formation rate in silicon under electrochemical anodization has been studied for different crystallographic directions. It was found that, for materials with doping levels NB=2·1019 (p++) cm-3 and NB=2.5·1017 cm-3 (p+), the propagation rates of the porous front grow with increasing concentration of hydrofluoric acid in aqueous electrolytes for all the crystallographic directions, whereas the anisotropy of the pore formation rate becomes weaker. For the material with NB=2.5·1017 cm-3, the direction <111> remains the predominant direction in which the porous layer is formed for all the electrolyte compositions.
Potential Synthesis of Solar-Grade Silicon from Rice Husk Ash
Authors: Ayomanor B.O. , Vernon-Parry Karen
Published: October 2015

Rice husk, an agricultural waste product obtained in large quantities in many countries including Nigeria, is very rich in siliceous materials. It has been known for several decades that, with careful processing, rice husk can be a source of metallurgical grade silicon [1]. The question remains as to whether rice husk ash (RHA) can be purified by a cost-effective, low technology route to produce solar-grade silicon suitable for use in photovoltaic devices. In Nigeria this would have the benefit of transforming large volumes (> 600,000 tonnes per annum) of agricultural waste into a partial solution to that country's issue with energy distribution.In this work, high purity silica has been prepared from RHA (ashed at 700°C for 5 and 12 hours) using a hydrometallurgical process. We report on the effect of natural variations in the rice husk composition on the effectiveness of the hydrometallurgical purification; the effectiveness of each stage of the hydrometallurgical process in removing impurity elements. While the hydrometallurgical purification of RHA is effective in removing impurities such as Ti and Fe to levels below the limits of detection of X-ray fluorescence (XRF), B and P levels need to be reduced to < 1017cm-3 well below the detection limits of XRF. The resultant silica has been subsequently reduced to metallurgical-grade silicon (MG-Si) by direct reduction using Mg powder.
Investigations of Critical Structural Defects in Active Layers of GaN-on-Si for Power Electronic Devices
Authors: Knetzger Michael , Meissner Elke , Derluyn Joff , Germain Marianne , Friedrich Jochen
Published: October 2015

The influence of structural defects in the active layer of GaN-on-Si substrates on the vertical leakage current was studied. The structural defects were analyzed by analytical scanning electron microscopy by means of cathodoluminescence (CL). The leakage current was determined by vertical I-V measurements.Two possibilities were found, which give potential explanations for the variations of the vertical leakage current: i) Threading dislocations, which may partially form leakage paths, were detected by CL imaging. ii) Variations of the carbon doping, which is used to tune GaN to a semi insulating material were revealed by CL spectroscopy.
Low-Frequency Noise Spectroscopy of Bulk and Border Traps in Nanoscale Devices
Authors: Simoen Eddy , Cretu Bogdan , Fang Wen , Aoulaiche Marc , Routoure Jean Marc , Carin Regis , Luo Jun , Zhao Chao , Claeys Cor
Published: October 2015

The principles and application of Generation-Recombination (GR) noise spectroscopy will be outlined and illustrated for the case of traps in Ultra-Thin Buried Oxide Silicon-on-Insulator nMOSFETs and for vertical polycrystalline silicon nMOSFETs. It will be shown that for scaled devices the GR noise is originating from a single defect, giving rise to a so-called Random Telegraph Signal (RTS). Several methods will be described for an accurate extraction of the RTS parameters (amplitude, up and down time constant). It will be demonstrated that besides the deep-level parameters also the position of the trap in the channel can be derived from a numerical modeling of the RTS amplitude.
Capacitance Transient Spectroscopy Measurements on High-k Metal Gate Field Effect Transistors Fabricated Using 28nm Technology Node
Authors: Mchedlidze Teimuraz , Drescher Maximilian , Erben Elke , Weber J.
Published: October 2015

Fast progress in nanometer-node high-k metal gate (HKMG) technology requires the development of versatile and detailed characterization methods for semiconductor / dielectric / metal stacks and interfaces between them. Complexity of the advanced fabrication processes does not allow preparation of model samples with dimensions used in standard laboratory measurements. In this report we apply capacitance transient spectroscopy measurements for the characterization of HKMG field effect transistors (FET) fabricated in the standard 28 nm node technology. Measurements were performed on n-FET devices. The devices were characterized in the as-fabricated stage, after application of electrical stress and after fluorine implantation introduced to passivate the interface carrier traps. Our results show good correspondence with those obtained by other characterization methods and supply detailed information on the energy distribution of the interface trap density in the system.
Discussion of ASi-Sii-Defect Model in Frame of Experimental Results on P Line in Indium Doped Silicon
Authors: Lauer Kevin , Möller Christian , Schulze Dirk , Ahrens Carsten , Vanhellemont Jan
Published: October 2015

Further experimental support for the ASi-Sii-defect as cause of light-induced degradation and as the defect responsible for a photoluminescence peak called P line in indium doped silicon is given. The ASi-Sii-defect model has two main implications related to oxygen clustering during Czochralski crystal growth and the common understanding of the boron interstitial defect. These implications are discussed and it is shown that the ASi-Sii-defect model is in agreement with available experimental data related to oxygen clustering and the boron interstitial defect.
Investigation into Efficiency-Limiting Defects in mc-Si Solar Cells
Authors: Al-Ani Oras A. , Sabaawi Ahmed M. A. , Goss J.P. , Cowern N.E.B. , Briddon P.R. , Rayson M.J.
Published: October 2015

First-principles quantum-chemical simulations are combined with TCAD device modelling to examine the impact of the intrinsic stacking faults and Σ5-(001) twist grain-boundaries on the performance of solar cell efficiency. We find from the combination of these computational methods, the optical properties of ideal stacking faults are similar to those of pure Si, whereas the optimised grainboundaryleads to a clear change in the real and imaginary parts of refractive index, increasing the solar-cell current density, and thus the solar cell efficiency. The impact at a device level is dependent upon the areal density of such material. So far as the optically absorption and carrier generation is concerned, segregation of diffusing iron at these planar defects has a negligible impact on device characteristics, but non-radiative recombination processes and carrier traps due to iron are expected to significantly affect efficiency in these regions.
Abundance, richness and root colonization of arbuscular mycorrhizal fungi in natural and semi-natural land use types at upper Hantana
Authors: Mafaziya Fathima , Madawala Sumedha
Published: October 2015

There is a scarcity of published information on the abundance and richness of arbuscular mycorrhizal fungi (AMF) in different natural and semi-natural land use types in Sri Lanka. The Upper Hantana (UH) area, which comprises land use types with different histories, was selected to fulfill this knowledge gap. A study was carried out to investigate the abundance and richness of AMF in selected land use types, including restored pine stand (REP), degraded grassland (DEG), Paraserianthes stand (PST) and natural forest patch (NFP) at Upper Hantana in the Central Province of Sri Lanka, were investigated. The highest AMF spore abundance was observed in the NFP. However, the AMF spore richness was higher in both NFP and REP than in DEG and PST. At NFP, the medium-sized spores dominate the AMF spore population. Furthermore, NFP showed the least evenness in AMF distribution compared to other land use types. Glomus was the most abundant genus in all selected land use types. Acaulospora was observed only in DEG and PST. The colonization potential of AMF varies highly between species and selected land use types with no clear relationship between AMF abundance and root colonization potential. The results speculate that AMF spore abundance is determined by the composition and diversity of the vegetation. The results also revealed that the AMF richness at REP was similar to that of NFP, indicating a positive impact on the below-ground biota within a relatively short period following restoration. Ceylon Journal of Science (Bio. Sci.) 44 (1) : 25-34, 2015
A refugium for Cordia subcordata (Boraginaceae), a very rare and endangered plant in Sri Lanka and strategies for its conservation
Authors: Jayasuriya A. H. Magdon , Gunatilleke I. A. U. Nimal
Published: October 2015

In Sri Lanka, Cordia subcordata Lam. was known only from three locations in the vicinity of Trincomalee Bay, the first collected in 1885, the second in 1939 and the third in 1974. This tree is presently found in an unprotected coastal forest bordering the Dutch Bay, north of Puttalam Lagoon which is the only known location elsewhere in Sri Lanka, and the first recorded on the western coast. As all original habitats in Trincomalee are now highly disturbed, the coastal forests in Aruwakkalu in the west coast are considered a refugium for this very rare and endangered plant. As only a Tamil name (“Lakshikottay”) has been recorded in Sri Lanka, the Sinhala name “Moodulolu” is proposed for this tree. Some strategies for conservation of this species and associated ecosystems and habitats are proposed. Ceylon Journal of Science (Bio. Sci.) 44 (1) : 67-70, 2015
The association of the JNK scaffold protein, WDR62, with the mixed lineage kinase 3, MLK3
Authors: Hadad Miriam , Aviram Sharon , Darlyuk-Saadon Ilona , Cohen-Katsenelson Ksenya , Whitmarsh Alan J. , Aronheim Ami
Published: October 2015

Mitogen-activated protein kinases (MAPKs) form a kinase tier module in which MAPK, MAP2K and MAP3K are held by scaffold proteins. The scaffold proteins serve as a protein platform for selective and spatial kinase activation. The precise mechanism by which the scaffold proteins function has not yet been fully explained. WD40-repeat protein 62, WDR62 is a novel scaffold protein of the c-Jun N-terminal kinase (JNK) pathway. WDR62 is a 1523 a.a. long protein with no significant sequence homology to a known gene. Previously WDR62 was shown to associate with JNK and MKK4/7 in a modular fashion. Here, we show that WDR62 is able to associate with multiple members of the MAP3K of the mixed lineage kinase family and we map WDR62-MLK3 interacting domains. We identify two separable interacting domains within WDR62 and MLK3 proteins that can cross associate. MLK3 association with WDR62 is independent of JNK and MKK4/7 domains and activities. CDC42 activation disrupts WDR62-MLK3 association independent of MLK3 kinase activity.
Use of the step-up action research model to improve trauma-related nursing educational practice
Authors: Seale Ielse , De Villiers Johanna C.
Published: October 2015

Background: A lack of authentic learning opportunities influence the quality of emergency training of nursing students. The purpose of this article is to describe how the step-up action research model was used to improve the quality of trauma-related educational practice of undergraduate nursing students.Objectives: To reduce deaths caused by trauma, healthcare workers should be competent to provide emergency care and collaborate effectively with one another.Method: A simulated mass casualty incident, structured to support the integration of theory into practice, became a more rigorous action research activity which focused on the quality improvement of the mass casualty incident.Results: The results indicated improved student learning; partnership appreciation; improved student coping mechanisms, and increased student exposure. Quality emergency training thus results in better real-life collaboration in emergency contexts.Conclusion: The step-up action research model proved to be a collaborative and flexible process. To improve the quality and rigour of educational programmes it is therefore recommended that the step-up action research model be routinely used in the execution of educational practices.
Human Immunodeficiency Virus-associated primary effusion lymphoma: An exceedingly rare entity in cerebrospinal fluid
Authors: Jain Sarika , Palekar Alka , Monaco Sara E. , Craig Fiona E. , Bejjani Ghassan , Pantanowitz Liron
Published: October 2015

Primary effusion lymphoma (PEL) in patients with Human Immunodeficiency Virus (HIV) infection may involve pleural, pericardial, and peritoneal cavities. PEL involving the cerebrospinal fluid (CSF) is exceedingly rare, and to our knowledge has only been reported in two cases. We report another case of PEL diagnosed in CSF from a 61-year-old male with Acquired Immunodeficiency Syndrome that presented with neurological symptoms. Imaging studies of his brain showed leptomeningeal/periventricular enhancement, but no mass lesion. His CSF demonstrated human herpesvirus-8 positive pleomorphic lymphoplasmacytoid cells of null cell phenotype. This case highlights that albeit rare, PEL should be included in the differential diagnosis when large atypical cells are encountered in CSF of HIV-positive patients, even when such patients have no history of lymphoma. As in this case, ancillary studies are required to make an accurate diagnosis of PEL in CSF cytology.
Interferences in photolytic NO2 measurements: explanation for an apparent missing oxidant?
Authors: Reed C. , Evans M. J. , Di Carlo P. , Lee J. D. , Carpenter L. J.
Published: October 2015

Abstract. Measurement of NO2 at low concentrations is non-trivial. A variety of techniques exist, with the conversion of NO2 into NO followed by chemiluminescent detection of NO being prevalent. Historically this conversion has used a catalytic approach (Molybdenum); however this has been plagued with interferences. More recently, photolytic conversion based on UV-LED irradiation of a reaction cell has been used. Although this appears to be robust there have been a range of observations in low NOx environments which have measured higher NO2 concentrations than might be expected from steady state analysis of simultaneously measured NO, O3, JNO2 etc. A range of explanations exist in the literature most of which focus on an unknown and unmeasured "compound X" that is able to convert NO to NO2 selectively. Here we explore in the laboratory the interference on the photolytic NO2 measurements from the thermal decomposition of peroxyacetyl nitrate (PAN) within the photolysis cell. We find that approximately 5 % of the PAN decomposes within the instrument providing a potentially significant interference. We parameterize the decomposition in terms of the temperature of the light source, the ambient temperature and a mixing timescale (∼ 0.4 s for our instrument) and expand the parametric analysis to other atmospheric compounds that decompose readily to NO2 (HO2NO2, N2O5, CH3O2NO2, IONO2, BrONO2, Higher PANs). We apply these parameters to the output of a global atmospheric model (GEOS-Chem) to investigate the global impact of this interference on (1) the NO2 measurements and (2) the NO2 : NO ratio i.e. the Leighton relationship. We find that there are significant interferences in cold regions with low NOx concentrations such as Antarctic, the remote Southern Hemisphere and the upper troposphere. Although this interference is likely instrument specific, it appears that the thermal decomposition of NO2 within the instrument's photolysis cell may give an explanation for the anomalously high NO2 that has been reported in remote regions, and would reconcile measured and modelled NO2 to NO ratios without having to invoke novel chemistry. Better instrument characterization, coupled to instrumental designs which reduce the heating within the cell seem likely to minimize the interference in the future, thus simplifying interpretation of data from remote locations.
Oil and gas impacts on air quality in federal lands in the Bakken region: an overview of the Bakken Air Quality Study and first results
Authors: Prenni A. J. , Day D. E. , Evanoski-Cole A. R. , Sive B. C. , Hecobian A. , Zhou Y. , Gebhart K. A. , Hand J. L. , Sullivan A. P. , Li Y. , Schurman M. I. , Desyaterik Y. , Malm W. C. , Schichtel B. A. , Collett J. L.
Published: October 2015

Abstract. The Bakken formation contains billions of barrels of oil and gas trapped in rock and shale. Horizontal drilling and hydraulic fracturing methods have allowed for extraction of these resources, leading to exponential growth of oil production in the region over the past decade. Along with this development has come an increase in associated emissions to the atmosphere. Concern about potential impacts of these emissions on federal lands in the region prompted the National Park Service to sponsor the Bakken Air Quality Study over two winters in 2013–2014. Here we provide an overview of the study and present some initial results aimed at better understanding the impact of local oil and gas emissions on regional air quality. Data from the study, along with long term monitoring data, suggest that while power plants are still an important emissions source in the region, emissions from oil and gas activities are impacting ambient concentrations of nitrogen oxides and black carbon and may dominate recent observed trends in pollutant concentrations at some of the study sites. Measurements of volatile organic compounds also definitively show that oil and gas emissions were present in almost every air mass sampled over a period of more than four months.
Constraining the sensitivity of iodide adduct chemical ionization mass spectrometry to multifunctional organic molecules using the collision limit and thermodynamic stability of iodide ion adducts
Authors: Lopez-Hilfiker F. D. , Iyer S. , Mohr C. , Lee B. H. , D'Ambro E. L. , Kurtén T. , Thornton J. A.
Published: October 2015

Abstract. The sensitivity of a chemical ionization mass spectrometer (ions formed per number density of analyte) is fundamentally limited by the collision frequency between reagent ions and analyte, known as the collision limit, the ion-molecule reaction time, and the transmission efficiency of product ions to the detector. We use the response of a time-of-flight chemical ionization mass spectrometer (ToF-CIMS) to N2O5, known to react with iodide at the collision limit, to constrain the combined effects of ion-molecule reaction time, which is strongly influenced by mixing and ion losses in the ion-molecule reaction drift tube. A mass spectrometric voltage scanning procedure elucidates the relative binding energies of the ion adducts, which influence the transmission efficiency of molecular ions through the electric fields within the vacuum chamber. Together, this information provides a critical constraint on the sensitivity of a ToF-CIMS towards a wide suite of routinely detected multifunctional organic molecules for which no calibration standards exist. We describe the scanning procedure, collision limit determination, and show results from the application of these constraints to the measurement of organic aerosol composition at two different field locations.
Human land uses enhance sediment denitrification and N2O production in Yangtze lakes primarily by influencing lake water quality
Authors: Liu W. , Yao L. , Wang Z. , Xiong Z. , Liu G.
Published: October 2015

Abstract. Sediment denitrification in lakes alleviates the effects of eutrophication through the removal of nitrogen to the atmosphere as N2O and N2. However, N2O contributes notably to the greenhouse effect and global warming. Human land uses (e.g. agricultural and urban areas) strongly affect lake water quality and sediment characteristics, which, in turn, may regulate lake sediment denitrification and N2O production. In this study, we investigated sediment denitrification and N2O production and their relationships to within-lake variables and watershed land uses in 20 lakes from the Yangtze River basin in China. The results indicated that both lake water quality and sediment characteristics were significantly influenced by watershed land uses. N2O production rates increased with increasing background denitrification rates. Background denitrification and N2O production rates were positively related to water nitrogen concentrations but were not significantly correlated with sediment characteristics and plant community structure. A significant positive relationship was observed between background denitrification rate and percentage of human-dominated land uses (HDL) in watersheds. Structural equation modelling revealed that the indirect effects of HDL on sediment denitrification and N2O production in Yangtze lakes were mediated primarily through lake water quality. Our findings also suggest that although sediments in Yangtze lakes can remove large quantities of nitrogen through denitrification, they may also be an important source of N2O, especially in lakes with high nitrogen content.
Quantitative comparison between two different methodologies to define rainfall thresholds for landslide forecasting
Authors: Lagomarsino D. , Segoni S. , Rosi A. , Rossi G. , Battistini A. , Catani F. , Casagli N.
Published: October 2015

Abstract. This work proposes a methodology to compare the forecasting effectiveness of different rainfall threshold models for landslide forecasting. We tested our methodology with two state-of-the-art models, one using intensity–duration thresholds and the other based on cumulative rainfall thresholds. The first model identifies rainfall intensity–duration thresholds by means of a software program called MaCumBA (MAssive CUMulative Brisk Analyzer) (Segoni et al., 2014a) that analyzes rain gauge records, extracts intensity (I) and duration (D) of the rainstorms associated with the initiation of landslides, plots these values on a diagram and identifies the thresholds that define the lower bounds of the I–D values. A back analysis using data from past events is used to identify the threshold conditions associated with the least number of false alarms. The second model (SIGMA) (Sistema Integrato Gestione Monitoraggio Allerta) (Martelloni et al., 2012) is based on the hypothesis that anomalous or extreme values of accumulated rainfall are responsible for landslide triggering: the statistical distribution of the rainfall series is analyzed, and multiples of the standard deviation (σ) are used as thresholds to discriminate between ordinary and extraordinary rainfall events. The name of the model, SIGMA, reflects the central role of the standard deviations. To perform a quantitative and objective comparison, these two models were applied in two different areas, each time performing a site-specific calibration against available rainfall and landslide data. For each application, a validation procedure was carried out on an independent data set and a confusion matrix was built. The results of the confusion matrixes were combined to define a series of indexes commonly used to evaluate model performances in natural hazard assessment. The comparison of these indexes allowed to identify the most effective model in each case study and, consequently, which threshold should be used in the local early warning system in order to obtain the best possible risk management. In our application, none of the two models prevailed absolutely over the other, since each model performed better in a test site and worse in the other one, depending on the characteristics of the area. We conclude that, even if state-of-the-art threshold models can be exported from a test site to another, their employment in local early warning systems should be carefully evaluated: the effectiveness of a threshold model depends on the test site characteristics (including the quality and quantity of the input data), and a validation procedure and a comparison with alternative models should be performed before its implementation in operational early warning systems.
Soil contaminations in landfill: a case study of the landfill in Czech Republic
Authors: Adamcová D. , Vaverková M. D. , Bartoň S. , Havlíček Z. , Břoušková E.
Published: October 2015

Abstract. Phytotoxicity test was determined to assess ecotoxicity of landfill soil. Sinapis alba L. was used as heavy metals bioindicator. Soil samples 1–8, which were taken from the landfill body, edge of the landfill body and its vicinity meet the limits for heavy metals Co, Cd, Pb, and Zn specified in the applicable legislation. Hg and Mn threshold values are not established in legislation, but values have been determined for the needs of the landfill operator. For heavy metals Cr, Cu, and Ni sample 2 exceeded the threshold values, which attained the highest values of all the samples tested for Cr, Cu and Ni. For Cr and Ni the values were several times higher than values of the other samples. The second highest values for Cr, Cu, and Ni showed sample 6 and 7. Both samples exceeded the set limits. An increase in plant biomass was observed in plants growing on plates with soil samples, but no changes in appearance, slow growth or necrotic lesions appeared. Ecotoxicity tests show that tested soils (concentration of 50 %) collected from the landfill body, edge of the landfill body and its vicinity reach high percentage values of germination capacity of seeds of Sinapis alba L. (101–137 %). At a concentration of 25 %, tested soil samples exhibit lower values of germination capacity; in particular samples 3 to 8, yet the seed germination capacity in all 8 samples of tested soils range between 86 and 137 %.
Nietzsche's Existentialist Freedom
Authors: Tubert Ariela
Published: October 2015

Following Robert C. Solomon's Living with Nietzsche, I defend an interpretation of Nietzsche's views about freedom that are in line with the existentialist notion of self-creation. Given Nietzsche's emphasis on the limitations on human freedom, his critique of the notion of causa sui (self-creation out of nothing), and his critique of morality for relying on the assumption that we have free will, it may be surprising that he could be taken seriously as an existentialist—existentialism characteristically takes freedom and self-creation to be central to the human condition. Nietzsche does not endorse a radical notion of freedom; he is rather emphatically critical of any such notion. However, I argue that he does have room for a certain kind of freedom and self-creation that supports Solomon's characterization of him as an existentialist.
Solution-Phase Crosstalk and Regulatory Interactions Between Multipotent Adult Progenitor Cells and Peripheral Blood Mononuclear Cells
Authors: Burrows Gregory G. , van't Hof Wouter , Reddy Ashok P. , Wilmarth Phillip A. , David Larry L. , Raber Amy , Bogaerts Annelies , Timmerman Lien , Pinxteren Jef , Roobrouck Valerie D. , Deans Robert J. , Maziarz Richard T.
Published: October 2015

Multipotent adult progenitor cells (MAPCs) are adult adherent stromal stem cells currently being assessed in clinical trials for acute graft versus host disease with demonstrated immunomodulatory capabilities and the potential to ameliorate detrimental autoimmune and inflammation-related processes. Anti-CD3/anti-CD28 (3/28) activation of T cells within the peripheral blood mononuclear cell (PBMC) compartment was performed in the presence or absence of MAPCs. Liquid chromatography-coupled tandem mass spectrometry was used to characterize the differential secretion of proteins, and transcriptional profiling was used to monitor mRNA expression changes in both cell populations. Overall, 239 secreted and/or ectodomain-shed proteins were detected in the secretomes of PBMCs and MAPCs. In addition, 3/28 activation of PBMCs induced differential expression of 2,925 genes, and 22% of these transcripts were differentially expressed on exposure to MAPCs in Transwell. MAPCs exposed to 3/28-activated PBMCs showed differential expression of 1,247 MAPC genes. Crosstalk was demonstrated by reciprocal transcriptional regulation. Secretome proteins and transcriptional signatures were used to predict molecular activities by which MAPCs could dampen local and systemic inflammatory responses. These data support the hypothesis that MAPCs block PBMC proliferation via cell cycle arrest coupled to metabolic stress in the form of tryptophan depletion, resulting in GCN2 kinase activation, downstream signaling, and inhibition of cyclin D1 translation. These data also provide a plausible explanation for the immune privilege reported with administration of donor MAPCs. Although most components of the major histocompatibility complex class II antigen presentation pathway were markedly transcriptionally upregulated, cell surface expression of human leukocyte antigen-DR is minimal on MAPCs exposed to 3/28-activated PBMCs.

Significance

This study documents experiments quantifying solution-phase crosstalk between multipotent adult progenitor cells (MAPCs) and peripheral blood mononuclear cells. The secretome and transcriptional changes quantified suggest mechanisms by which MAPCs are hypothesized to provide both local and systemic immunoregulation of inflammation. The potential impact of these studies includes development of a robust experimental framework to be used for preclinical evaluation of the specific mechanisms by which beneficial effects are obtained after treatment of patients with MAPCs.
Concise Review: Understanding the Renal Progenitor Cell Niche In Vivo to Recapitulate Nephrogenesis In Vitro
Authors: Mari Chiara , Winyard Paul
Published: October 2015

Chronic kidney disease (CKD), defined as progressive kidney damage and a reduction of the glomerular filtration rate, can progress to end-stage renal failure (CKD5), in which kidney function is completely lost. CKD5 requires dialysis or kidney transplantation, which is limited by the shortage of donor organs. The incidence of CKD5 is increasing annually in the Western world, stimulating an urgent need for new therapies to repair injured kidneys. Many efforts are directed toward regenerative medicine, in particular using stem cells to replace nephrons lost during progression to CKD5. In the present review, we provide an overview of the native nephrogenic niche, describing the complex signals that allow survival and maintenance of undifferentiated renal stem/progenitor cells and the stimuli that promote differentiation. Recapitulating in vitro what normally happens in vivo will be beneficial to guide amplification and direct differentiation of stem cells toward functional renal cells for nephron regeneration.

Significance

Kidneys perform a plethora of functions essential for life. When their main effector, the nephron, is irreversibly compromised, the only therapeutic choices available are artificial replacement (dialysis) or renal transplantation. Research focusing on alternative treatments includes the use of stem cells. These are immature cells with the potential to mature into renal cells, which could be used to regenerate the kidney. To achieve this aim, many problems must be overcome, such as where to take these cells from, how to obtain enough cells to deliver to patients, and, finally, how to mature stem cells into the cell types normally present in the kidney. In the present report, these questions are discussed. By knowing the factors directing the proliferation and differentiation of renal stem cells normally present in developing kidney, this knowledge can applied to other types of stem cells in the laboratory and use them in the clinic as therapy for the kidney.
Vascular Smooth Muscle Cells From Hypertensive Patient-Derived Induced Pluripotent Stem Cells to Advance Hypertension Pharmacogenomics
Authors: Biel Nikolett M. , Santostefano Katherine E. , DiVita Bayli B. , El Rouby Nihal , Carrasquilla Santiago D. , Simmons Chelsey , Nakanishi Mahito , Cooper-DeHoff Rhonda M. , Johnson Julie A. , Terada Naohiro
Published: October 2015

Studies in hypertension (HTN) pharmacogenomics seek to identify genetic sources of variable antihypertensive drug response. Genetic association studies have detected single-nucleotide polymorphisms (SNPs) that link to drug responses; however, to understand mechanisms underlying how genetic traits alter drug responses, a biological interface is needed. Patient-derived induced pluripotent stem cells (iPSCs) provide a potential source for studying otherwise inaccessible tissues that may be important to antihypertensive drug response. The present study established multiple iPSC lines from an HTN pharmacogenomics cohort. We demonstrated that established HTN iPSCs can robustly and reproducibly differentiate into functional vascular smooth muscle cells (VSMCs), a cell type most relevant to vasculature tone control. Moreover, a sensitive traction force microscopy assay demonstrated that iPSC-derived VSMCs show a quantitative contractile response on physiological stimulus of endothelin-1. Furthermore, the inflammatory chemokine tumor necrosis factor α induced a typical VSMC response in iPSC-derived VSMCs. These studies pave the way for a large research initiative to decode biological significance of identified SNPs in hypertension pharmacogenomics.

Significance

Treatment of hypertension remains suboptimal, and a pharmacogenomics approach seeks to identify genetic biomarkers that could be used to guide treatment decisions; however, it is important to understand the biological underpinnings of genetic associations. Mouse models do not accurately recapitulate individual patient responses based on their genetics, and hypertension-relevant cells are difficult to obtain from patients. Induced pluripotent stem cell (iPSC) technology provides a great interface to bring patient cells with their genomic data into the laboratory and to study hypertensive responses. As an initial step, the present study established an iPSC bank from patients with primary hypertension and demonstrated an effective and reproducible method of generating functional vascular smooth muscle cells.
On Universal Point Sets for Planar Graphs
Authors: Cardinal Jean , Hoffmann Michael , Kusters Vincent
Published: October 2015

A set P of points in R2 is n-universal if every planar graph on n vertices admits a plane straight-line embedding on P. Answering a question by Kobourov, we show that there is no n-universal point set of size n, for any n ≥ 15. Conversely, we use a computer program to show that there exist universal point sets for all n ≤ 10 and to enumerate all corresponding order types. Finally, we describe a collection G of 7′393 planar graphs on 35 vertices that do not admit a simultaneous geometric embedding without mapping, that is, no set of 35 points in the plane supports a plane straight-line embedding of all graphs in G.
Rumores de festa: o sagrado e o profano na Bahia
Authors: Serra Ordep
Published: October 2015

Esse livro aborda o cambiante movimento das festas populares baianas, um fenômeno que hoje suscita grande interesse de estudiosos e do público em geral. Ele chama a atenção para transformações, fazendo referências a etapas anteriores e esboçando tentativas de sondar desenvolvimentos futuros. Preenche importante lacuna na bibliografia acerca do tema abordado.
Tempo de Festas: homenagens a Santa Bárbara, Nossa Senhora da Conceição e Sant’Ana em Salvador (1860-1940)
Authors: Souza Couto Edilece
Published: October 2015

O livro faz um estudo sobre três festas: Santa Bárbara, Conceição da Praia e Sant’Ana. Apesar de possuírem características comuns, as devoções surgiram em épocas diferentes, são realizadas em distantes localidades da cidade e atraem um público também diversificado, de acordo com as posições ocupadas na hierarquia das associações católicas e as atividades profissionais dos seus organizadores. O livro, dividido em cinco capítulos, traz uma nova contextualização das festas. A partir dos relatos documentados pelos que viveram essas experiências, o leitor viajará pelo mundo lúdico desses importantes patrimônios culturais.
Influences of source conditions on mountain wave penetration into the stratosphere and mesosphere
Authors: Kaifler Bernd , Kaifler Natalie , Ehard Benedikt , Dörnbrack Andreas , Rapp Markus , Fritts David C.
Published: October 2015

We present atmospheric gravity wave (GW) measurements obtained by a Rayleigh/Raman lidar at Lauder, New Zealand, (45°S, 170°E) during and after the Deep Propagating Gravity Wave Experiment campaign. GW activity and characteristics are derived from 557 h of high‐resolution lidar data recorded between June and November 2014 in an altitude range between 28 and 76 km. In this period, strong GW activity occurred in sporadic intervals lasting a few days. Enhanced stratospheric GW potential energy density is detected during periods with high tropospheric wind speeds perpendicular to New Zealand's Southern Alps. These enhancements are associated with the occurrence of quasi‐stationary GW (mountain waves). Surprisingly, the largest response in the mesosphere is observed for conditions with low to moderate lower tropospheric wind speeds (2–12 m/s). On the other hand, large‐amplitude mountain waves excited by strong tropospheric forcings often do not reach mesospheric altitudes, either due to wave breaking and dissipation in the stratosphere or refraction away from New Zealand.