bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Static Dielectric Constant (ε0) and Refractive Index (n) Using Various Models for Binary Mixtures (Acetophenone with N-Hexanol)
Authors: Prajapati A.N.
Published: August 2016

Static dielectric constant (ε0) and refractive index (n) have been experimentally determined for binary liquid mixture of n-Hexanol (HxOH) with Acetophenone (ACP) over the entire concentration range of mixture composition (0.0 →1.0) at constant temperature 303.15 K. Static dielectric constant (ε0) and refractive index (n) for the binary mixture have been measured using high precision LCR meter (0.2 MHz) and Abbe’s refractometer respectively. Excess of static dielectric constant (ε0)E and refractive index (n)E are determined and fitted with Redlich-Kister polynomial equation to derive the binary coefficients and standard deviations. Deviations of these parameters are discussed in terms of terms of molecular interaction between the constituent species. In the present work, comparative study of various mixing models for static dielectric constant (ε0) [Böttcher-Bordewijk (BOTT), Bruggeman (BRUG), Kraszewski (KRAZ), Looyenga (LOOY), Peon–Iglesias (P-I)] and for refractive index (n) [Oster (OST), Weiner (W), Eykman (EYK), Lorentz–Lorentz (L-L), Arago–Biot (A-G), Newton (Nw), Gladstone–Dale (G-D) and Erying–John (EJ)] have been carried out and their validity has been tested for the (n-HxOH+ACP) binary mixtures. The objective of the present work is to report the influence of nonassociative molecule on the molecular dynamics of associative molecules and validation mixing models.
Structural Properties of In1-xSnx at Different Concentrations and Temperatures
Authors: Patel C.H. , Patel Amit B. , Bhatt Nisarg K. , Gajjar P.N.
Published: August 2016

The partial structure factors for liquid alloy In1-xSnx have been computed at varying concentration and temperatures using pseudopotential theory. The structure factor S(q) and pair correlation function g (r) have been determined using the hard-sphere approximation. The temperature dependent hard-sphere diameter σ (T) is estimated using Vσ=Vminr+12kBT criterion from the computed pair potential. The modified empty-core local pseudopotential, which represents the orthogonalisation effect due to s-core states, is used for electron–ion interaction with proper screening function. The only potential parameter, the core radius, is determined at different temperatures from the knowledge of structure factor. Intrinsic temperature effects have been studied through dimensionless damping term (see formula in paper) in the pair potential. The effect of temperature and concentration on structure factors is discussed to shed light on bonding in technologically important alloy. This used pseudopotential proved successful in explaining the structural properties of non-crystalline alloys at higher temperatures.
Phonons in Binary Metallic Glass CuZr
Authors: Khambholja S.G. , Thakore Brijmohan Y. , Jani Ashvin R.
Published: August 2016

In the present paper, we have reported the results of our computational study of phonon frequencies in binary metallic glass CuZr2. Model potential formalism is used here along with two different approaches namely due to Hubbard and Beeby (HB) as well as due to Takeno and Goda (TG). The results are compared with the recent experimental results and the possible ways of improvements in the results are also discussed. Further, sound velocities are also reported.
Dynamical Variable of Bi50Zn50 Bulk Metallic Glass at Various Temperature
Authors: Suthar P.H.
Published: August 2016

The theoretical study of dynamical variables: velocity autocorrelation function (VACF), power spectrum (PS) and mean square displacement (MSD) of Bi50Zn50 bulk metallic glass at T= 793K, 873K, 1023K and 1123K have been calculated based on the static harmonic well approximation. The effective interatomic potential for bulk metallic glass is computed using our established model potential with the exchange correlation functions due to Farid et al. It is observed that negative dip in velocity auto correlation function decreases as the temperature increases. In the power spectrum as temperature increases, the peak of power spectrum shifts toward lower ω. The obtained result of MSD concludes that the vibrating component in the atomic motion is decreases as increases the temperatures.
Ab Initio Study of Structural Phase Transition and Electronic Properties in Samarium (Sm) Compounds
Authors: Panwar Yeshvir Singh , Aynyas Mahendra , Pataiya Jagdeesh , Sanyal Sankar P.
Published: August 2016

The electronic structure and high pressure structural phase transition of SmTe and SmPo have been studied by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is obtained and it is found that these compounds are stable in NaCl-type (B1-phase) structure and transform to CsCl-type (B2-type) structure. The transition pressure of SmTe and SmPo are found to be 6.6 GPa and 8.6 GPa respectively. We have also calculated lattice parameter (a0), bulk modulus (B0), band structure (BS) and density of states (DOS). From energy band diagram, we observed that these compounds exhibit weakly metallic behaviour. The calculated values of lattice parameter and bulk modulus agree well with the available data.
Synthesis of Nano-Barium Titanate and Application for Strontium Adsorption from Aqueous Solution
Authors: Saravaia Hitesh , Gupta Hariom , Kulshreshtha Vaibhav
Published: August 2016

Barium Titanate (BaTiO3) nanostructures are synthesized by the molten salt-hydroxide reaction. The crystalline phase and chemical structure of the synthesized material are analyzed using powder x-ray diffraction (XRD) and FT-IR techniques, revealing the tetragonal BaTiO3 crystalline structure. Morphology and thermal stability of the material are characterized using TEM and TG-DTG analysis. BET surface area analysis shows significant active surface available for adsorption and its surface area value is found to be 14.8427 m2 g-1. The maximum adsorption of strontium metal is found to be 56.3 for the 1.2 g L-1 BaTiO3 adsorbent dose which reveals a remarkable separation property of the BaTiO3.
First Principles Study of Electronic, Lattice Dynamic, and Thermal Properties of Single Layer Phosphorene
Authors: Mir Showkat H. , Pillai Sharad B. , Som Narayan N. , Jha Prakash C. , Jha Prafulla K.
Published: August 2016

Heat removal is a fundamental issue for continuous progress in the electronic industry and for the thermal management in electronic devices. Materials with high thermal conductivity may help in the elimination of excess heat more efficiently which is necessary for improving the device performance. Phosphorene is a 2D material that has been recently exfoliated mechanically. Using density functional theory, we presented the electronic, lattice dynamic, thermal and dielectric properties of phosphorene. It is found that sound velocity is larger along the zigzag direction signifying anisotropic thermal behaviour. The macroscopic dielectric constant calculated is also found to be anisotropic in nature. Finally, the variation of entropy and specific heat with temperature is obtained.
Infrared Spectra of Electronically Doped Polythiophene
Authors: Parmar Hitesh , Shah R.K. , Oza A.T.
Published: August 2016

Polythiophene was prepared by oxidation of thiophene. It was electronically doped with organic acceptors such as TCNE, TCNQ, DDQ, Chloranil and kI-I2. The FTIR spectra revealed only little change of intermolecular band gap of about 0.21ev of polythiophene .However, polythiophene (pure) obtained from chemical company revealed degenerate semiconducting property. The electronic doping with the organic acceptors and kI-I2 revealed optical properties in small polaron model in the FTIR range. Thus both non-degenerate and degenerate polythiophenes were studied with 60% doping of organic acceptors.
Comparison of Hot Electron Mobility in h-Boron Nitride Nanosheets and Graphene under Manganese Doping
Authors: Pandya Ankur , Shinde Satyam , Jha Prafulla K.
Published: August 2016

The electron mobility is calculated for h-BN nanosheets (h-BNNSs) and graphene with and without doping of manganese at high electric fields via acoustical deformation potential (ADP) scattering mechanism and piezoelectric scattering (Polar Acoustical Phonon (PAP) mechanism at low temperatures. Calculation includes the variation of electron Fermi energy and effective mass with high electric fields and with variation of Mn concentrations. Comparison of mobility in both the cases of with and without doping is carried out. It is observed that the net electron mobility due to both ADP and PAP mechanisms in graphene is much larger than that for h-BNNS for both the cases of with and without doping of manganese at low temperatures.
High Pressure Structural and Mechanical Properties of YBi and ScBi Compounds
Authors: Ahirwar Ashok K. , Aynyas Mahendra , Panwar Yeshvir Singh , Sanyal Sankar P.
Published: August 2016

A theoretical study of first order pressure induced structural phase transition, mechanical and thermal properties of YBi and ScBi compounds have been investigated using the modified inter-ionic potential theory (MIPT), which parametrically includes the effect of coulomb screening. The calculated results of phase transition pressure of ScBi and YBi are agree well with the available theoretical data. We have also reported the second order elastic constants and Debye temperature of these compounds. Our calculated values of second order elastic constant C11, C12 and C44 are 128.4, 29.5, 30.2 GPa and 123.1, 29.7, 30.3 GPa for ScBi and YBi compounds respectively. These results are in good agreement with available theoretical data. We have also estimated Debye temperatures (θD) are 80K, 86K, for ScBi and YBi compounds respectively.
Frohlich Interaction in Compound Semiconductors: A Comparative Study
Authors: Dubey Swati , Paliwal Ayushi , Ghosh S.
Published: August 2016

In polar semiconductor materials, LO phonons produce a macroscopic electric field, which interacts with the electrons. This coupling of long range is known as Frohlich interaction. Due to the interaction of an electron with LO phonons, a quasi-particle is formed known as polaron. The strength of this coupling is expressed by a dimensionless Frohlich coupling constant. Due to the polar coupling to LO phonons, the carriers lose their initial kinetic energy to the lattice by a very efficient relaxation mechanism in III-V bulk semiconductors. Therefore it would be interesting to examine the effect of Frohlich coupling constant on the operational characteristics of optical parametric interaction in compound semiconductor medium. Using hydrodynamic model and coupled mode theory, a theoretical model is developed to determine threshold pump field for the onset of parametric process. For the sake of numerical estimations, data of ZnS and GaAs have been used. These prominent materials are assumed to be shined by a 10.6 μm CO2 laser so that nonlinearity could be induced in the medium. It is found that material having lower coupling constant is beneficial for a cost effective parametric interaction. It is hoped that result of this paper may be useful for various industrial applications.
Analyzing TEM Images for Accurate Determination of Lattice Parameters of Vacuum Evaporated SnSe Thin Film by Image Processing Software
Authors: Zankat Chetan , Pathak V.M. , Pataniya Pratik , Solanki G.K. , Patel K.D. , Nair Salil , Joy Jolly Mary
Published: August 2016

Amorphous SnSe thin films were deposited by thermal evaporation technique on glass substrates kept at room temperature in a vacuum better than 10-5Torr. A detailed study of structural and optical properties of 150 nm thin film was carried out. The selected area diffraction patterns obtained by TEM for this thin film were analyzed by a new method that involves accurate determination of lattice parameters by image processing software. The obtained results are in good agreement with the JCPDS data. Optical transmission spectra obtained at room temperature were analyzed to study optical properties of deposited thin films. It has been found that indirect carrier transition is responsible for optical absorption process in the deposited thin films.
Magnetic and Dielectric Properties of Barium Magnesium Hexaferrite Epoxy Resin Composite Film
Authors: Chauhan Chetna , Nandotaria Reshma , Jotania Rajshree
Published: August 2016

The W type barium magnesium hexaferrite powder with chemical composition BaMg2Fe16O27with CTAB surfactant was synthesized using solvent free synthesis method. The precursor was calcinated at 950 °C for 6 h in a muffle furnace and then slowly cooled to room temperature in order to obtain barium magnesium hexaferrite powder. The flexible epoxy thick film of Ba-Mg hexaferrite/epoxy composite was fabricated using suitable amount of hardener and curing agent. The field-dependent magnetic properties of the hexaferrite sample were investigated at room temperature using a vibrating sample magnetometer (VSM) with a maximum applied field of 15 kOe. The dielectric measurements were taken at room temperature within the frequency range to 100 Hz to 2 MHz.
Insights from the Plant World: A Fractal Analysis Approach to Tune Mechanical Rigidity of Scaffolding Matrix in Thin Films
Authors: Bagchi Debjani , Dasgupta Avik , Gondaliya Amit D. , Rajput Kishore S.
Published: August 2016

Using a fractal analysis approach to study plant leaf venation and stem sections, we find that plants use very intelligent scaffolding strategies to tune mechanical strength of leaves and stems. Within plant organs, specialized types of tissues with different mechanical properties have evolved. Ideally, the biopolymers cellulose, hemicelluloses and lignin present in plant cell walls confer mechanical rigidity to plant tissues, but our studies reveal that the manner these biopolymers are distributed in the tissue matrix hold the key to the mechanical rigidity of the tissues. We have developed an algorithm to determine fractal dimension of the scaffolding matrix and the well-known box counting algorithm to calculate fractal dimensions of leaf venation in high resolution images of reticulate–veined leaves and optical microscope image of cellulose, hemicellulose, and lignin-stained cross sections of Turbina corymbosa. We found that in leaves with reticulate venation, veins form a scaffolding matrix imparting mechanical rigidity to leaves, and have a fractal dimension close to 1.0 for leaves which have less bending resistance, compared to fractal dimensions close to 1.7 for leaves which have higher bending resistance. Deriving this idea from plants, we use evaporation instability to develop scaffolding matrix with fractal dimensions higher than 1.5 in polymer films. This can form the basis of an efficient strategy to devise thin, stand-alone polymer films with tunable bending stiffness.
Temperature Effects on Dynamical Conductivity of Graphene Based Systems
Authors: Patel D.K. , Ambavale S.K. , Prajapati K.J. , Sharma A.C.
Published: August 2016

We have investigated dynamical conductivity of graphene based systems; Single Layer Graphene (SLG), Bilayer Graphene (BLG) and Single Layer Gapped Graphene (SLGG), at zero and finite temperatures by taking into the account screening effects within the Random Phase Approximation (RPA). Rσq,ω and Rσq,ω show peaks that correspond to single particle excitations (SPE) and collective excitations (CE) respectively. In SLG, SPE positions are observed at ωħ≈0.5εf,εf∧1.5εf for q0.5kf,kf∧1.5kf respectively for all values of temperature. The peak height increases with increasing electron momentum and temperature. We noticed that for finite momentumq0.5kf∧kf, the peak height is maximum for T=0K and minimum for T=0.5Tf while that for T=Tf is intermediate. We also noticed that Rσq,ω peaks are blue shifted at high temperature for all graphene systems. In case of BLG, Landau undamped peak has been observed at T=0 for finite momentumq=0.3kf which becomes smooth at T=0.5Tf∧Tf. For q=0.8kf, Landau damped plasmon peaks have also been observed for all values of temperature. No major changes are observed in case of SLGG, with respect to SPE and CE peaks positions and heights specifically due to small change in band gap value incorporated here.
Structural, Thermal and Optical Properties of Nickel Oxide (NiO) Nanoparticles Synthesized by Chemical Precipitation Method
Authors: Deshpande M.P. , Patel Kiran N. , Gujarati Vivek P. , Patel Kamakshi , Chaki S.H.
Published: August 2016

Nanocrystalline NiO has been prepared successfully by chemical precipitation route using nickel nitrate hexahydrate (Ni (NO3)2·6H2O) and sodium hydroxide (NaOH) aqueous solution at a temperature of 60 ̊C. Their compositional, structural, morphological, thermal and optical properties were studied using energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence (PL) spectroscopy and Raman spectroscopy. From XRD pattern we confirmed the face centered cubic (fcc) structure of the synthesized NiO nanoparticles. The selected area electron diffraction (SAED) pattern indicated the same crystalline planes as seen in XRD pattern. TGA indicates good thermal stability of synthesized NiO nanoparticles and the optical absorption spectrum of NiO nanoparticles shows the strong absorption edge at 235nm (4.10eV). PL spectra of NiO nanoparticles shows two wide emission peaks at 420nm (2.95eV) and 440nm (2.82eV) and a strong–broad peak at 460nm (2.70eV) in violet emission band whereas the Raman peak observed at 518cm-1 shows the Ni-O stretching mode of vibration.
Influence of Chain Length of 1D Thermal Transistor on Thermal Amplification Factor
Authors: Vachhani M.G. , Gajjar P.N.
Published: August 2016

We study the influence of chain length of our 1D model of thermal transistor on thermal amplification factor. Here, we varied the length of drain and source segments for different simulation experiment and found that the maximum value of thermal amplification factor influenced with chain length. The thermal amplification factor of the thermal transistor is found to be dependent on gate temperature. We also calculated the switching efficiency and working region of the thermal transistor and better results are obtained in comparison to previous study.
First Principles Study of Structural and Electronic Properties of ErX (X=Cu, Ag and Au) Intermetallics
Authors: Shugani Mani , Aynyas Mahendra , Pawar Harsha , Sanyal Sankar P.
Published: August 2016

The electronic structures, densities of states and Fermi surfaces of ErX (X = Cu, Ag and Au) intermetallic compounds are studied using full potential linear augmented plane wave (FP-LAPW) method within generalized gradient approximation (GGA) for the exchange-correlation functional. The total energies are computed as a function of volume and fitted to the Birch equation of state. The ground state properties such as equilibrium lattice constants (a0), bulk modulus (B) and pressure derivative of bulk modulus (B') and density of states at the Fermi level N (EF) are calculated. The states at the Fermi level (EF) are dominated by Er ‘d’ states with significant contribution of ‘p’ and ‘d’ states of X. We have also plotted charge density and Fermi surface to study the bonding properties of ErX compounds.
Effect of Temperature/Pressure on Lattice Dynamics of FeNi
Authors: Pandya N.Y. , Mevada A.D. , Gajjar P.N.
Published: August 2016

Tetratenite phase of L10 (CuAu) FeNi is identified as a hard ferromagnet in spite of that common FeNi alloys are classified as a soft magnet. Due to its strong magnetic anisotropy and large coercivity, tetrataenite phase of L10 FeNi is under investigation as a rare earth free advanced permanent magnet. Our computed equilibrium lattice constant and c/a ratio for tetratenite phase of L10 (CuAu) FeNi are in 10 % deviation with the other available results. The vibrational and electronic properties of L10 FeNi at finite temperatures/pressures are studied using the first-principles plane wave self-consistent method under the framework of density functional theory. Conclusions based on the phonon dispersion curves, phonon density of states and electronic band structure along with total and projected density of states at finite temperatures/pressures are outlined.
Vibrational and Elastic Properties of Bulk Metallic Glass: Application to Pd64Fe16P20
Authors: Chauhan Payal N. , Prakruti Chaudhari , Joshi R.H. , Bhatt Nisarg K. , Thakore Brijmohan Y.
Published: August 2016

Different elastic properties of Pd-based Pd64Fe16P20 have been computed using two different forms of pseudopotential. Both the forms differ within the core region suggesting different degrees of orthogonalization and its r-dependence, while outside the core both preserves the Columbic nature. The only parameter, the core radius, separates these regions, and it is calculated using the realistic assumption based on the nearest neighbor distance. Further, five different forms of the local field correlated functions, namely, Hartree (H), Taylor (T), Ichimaru and Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are examined for better understanding regarding the screening effect on different elastic constants for Pd64Fe16P20 bulk metallic glass. The calculated results for the various elastic moduli, Poisson's ratio, sound velocity and phonon dispersion curve are all found to be in general agreement with the available experimental data. This confirms the applicability of the model pseudopotential to bulk metallic systems.
Kairos moments and prophetic witness: Towards a prophetic ecclesiology
Authors: De Gruchy John
Published: August 2016

The thirtieth anniversary of the publication of the Kairos Document was celebrated in August 2015. This was the most radical of several theological declarations issued by Christians during the struggle against apartheid. Arguing that theology itself had become a site of that struggle, it rejected ‘state theology’, which gave legitimacy to apartheid, and ‘church theology’ which promoted reconciliation without justice as its pre-requisite. Against these, it presented a ‘prophetic theology’ as a challenge to the churches in response to what was perceived as a kairos moment. Since then the Kairos Document has inspired a global movement in which its social analysis and understanding of prophetic theology has been adopted in a variety of contexts, most notably in the Kairos-Palestine Document (2009). In reflecting on the significance of this global kairos movement, I firstly examine the meaning of ‘prophecy’ and ‘prophetic theology’, arguing that ‘prophetic theology’ is in continuity with the message of the Hebrew prophets and the ministry and mission of Jesus. Secondly, I examine the use of the term kairos to describe historical turning points which demand such a prophetic theological response. Thirdly, I address the need for an ecumenical prophetic ecclesiology that foregrounds the responsibility of the church to discern and understand those God-given kairos moments in history that demand a prophetic response.
Antecedents of citizenship behaviour in online customer communities: An empirical investigation
Authors: Mpinganjira Mercy
Published: August 2016

Background: Use of online communities for knowledge generation has become a common phenomenon. In order for online communities to serve as affective spaces for knowledge generation and exchange, members need to behave in ways that are in line with good citizenship. However, because of the limited research, not much is known about citizenship behaviour in such communities and the factors that foster such conduct.Objectives: This article aims to examine the performance of citizenship behaviours by members of online customer communities, and the factors that influence this.Methodology: Data were collected from 303 contributing members of online customer communities using a structured questionnaire. Structural equation modelling was used to analyse the data collected.Results: The findings show moderate levels of engagement in citizenship behaviours among the respondents. Engagement in citizenship behaviours was in general found to be influenced more by the level of affective commitment towards the community than by the perceived levels of social support. Both affective commitment and perceived social support were found to have less influence on compliant citizenship behaviour when compared with altruism and personal initiative. Affective commitment was found to influence personal initiative most strongly, while social support had its strongest influence on altruism. Conclusion: The results provide insights for managers of online customer communities into factors to which they should give attention in order to enhance the performance of citizenship behaviours.
Surface roughness of restorative materials after immersion in mouthwashes
Authors: Bohner Lauren Oliveira Lima , de Godoi Ana Paula Terossi , Ahmed Ahad Shahid , Neto Pedro Tortamano , Catirse Alma Blasida Concepcion Elizaur Benitez
Published: August 2016

Objective: To evaluate the surface roughness of resin composite and ceramic material after immersion in mouthwashes. Methodology: Thirty specimens of resin composite and ceramic material were prepared with a stainless steel matrix (6 mm × 2 mm). The samples of each material were divided into three groups (n = 10), according to the mouthwashes: Distilled water (DW), chlorhexidine (CL) 0.12%, and cetylpyridinium chloride (CC). Specimens were individually submitted to the immersion cycle in 15 mL of mouthwash for 30 days, three times per day, for 1 min/cycle. Surface roughness measurements were performed at three different time intervals: Before the first cycle (T0), after 7 (T1), and 30 days (T2) of immersion. Data were analyzed by the two-way ANOVA and Tukey tests (P ≤ 0.05). Results: There was no statistically significant difference in surface roughness of resin composite among mouthwashes (DW - 1.4 ± 0.13 μm; CL - 1.16 ± 0.13 μm; CC - 1.18 ± 0.13 μm). Surface roughness was statistically significantly lower after 30 days (T2-0.56 ± 0.60 μm) compared with the initial period (T0-1.63 ± 0.60 μm) and after 7 days (T1-1.57 ± 0.60 μm). For ceramic material, CC (3.75 ± 0.60 μm) caused a higher level of surface roughness compared with DW (2.57 ± 0.60 μm) and CL (3.39 ± 0.60 μm). There was no statistically significant difference among the different time intervals (T0-3.05 ± 0.18 μm; T1-3.41 ± 0.18 μm; T2-3.26 ± 0.18 μm). Conclusion: Mouthwashes did not promote a significant change in surface roughness of composite resin. Cetylpyridinium chloride promoted an increase in surface roughness of dental ceramic.
Physical properties of acrylic resin teeth submitted to toothbrushing and immersion in beverages
Authors: Pero Ana Carolina , Borghi Izabela , Marin Danny Omar Mendoza , Policastro Vivian Barnabé , de Oliveira Norberto Martins , Compagnoni Marco Antonio
Published: August 2016

Background: Brushing and consumption of dye beverages may alter the physical properties of artificial teeth. Objective: The objective of this study was to evaluate the effect of toothbrushing and immersion in beverages in roughness and color of two types of artificial teeth: Biotone (B) and Biotone interpenetrating polymer network (IPN). Materials and Methods: For each tooth, seven groups were formed (n = 10): Toothbrushing (T), toothbrushing + water (TW), toothbrushing + coke (TCk), toothbrushing + coffee (TCf), immersion in water (W), coke (Ck), coffee (Cf). Roughness and color stability evaluations were performed before treatment and after treatment. According to the group, 11,000 brushing cycles were performed and specimens were immersed in beverages for 12 days, both simulating a period of 1 year. Color variations were captured by a spectrophotometer and roughness was analyzed by a profilometer. Color data were analyzed using analysis of variance (ANOVA) and Least significant difference test whereas roughness data were analyzed using ANOVA and Bonferroni test, both with α=0.05. Results: For Biotone, clinical significant color changes according to National Bureau of Standards (NBS) units were observed for the Groups T, TW, W, and Ck, and the results of ∆E were statistically similar among them (P > 0.05). For Biotone IPN, clinical significant color changes were found for TCf (4.86 NBS units) and Cf (4.82), and the results of ∆E were also similar among them. Surface roughness Ra (μm), regardless of the teeth, was reduced for the groups submitted to toothbrushing whereas no significant differences were found among the Groups W, Ck, and Cf. Conclusions: Toothbrushing had no influence on the color stability but significantly reduced the roughness, irrespective of the type of tooth.
Measuring ice- and liquid-water properties in mixed-phase cloud layers at the Leipzig Cloudnet station
Authors: Bühl Johannes , Seifert Patric , Myagkov Alexander , Ansmann Albert
Published: August 2016

Abstract. An analysis of the Cloudnet data set collected at Leipzig, Germany, with special focus on mixed-phase layered clouds is presented. We derive liquid- and ice-water content together with vertical motions of ice particles falling through cloud base. The ice mass flux is calculated by combining measurements of ice-water content and particle Doppler velocity. The efficiency of heterogeneous ice formation and its impact on cloud lifetime is estimated for different cloud-top temperatures by relating the ice mass flux and the liquid-water content at cloud top. Cloud radar measurements of polarization and Doppler velocity indicate that ice crystals formed in mixed-phase cloud layers with a geometrical thickness of less than 350 m are mostly pristine when they fall out of the cloud.
Evaluating secondary inorganic aerosols in three dimensions
Authors: Mezuman Keren , Bauer Susanne E. , Tsigaridis Kostas
Published: August 2016

Abstract. The spatial distribution of aerosols and their chemical composition dictates whether aerosols have a cooling or a warming effect on the climate system. Hence, properly modeling the three-dimensional distribution of aerosols is a crucial step for coherent climate simulations. Since surface measurement networks only give 2-D data, and most satellites supply integrated column information, it is thus important to integrate aircraft measurements in climate model evaluations. In this study, the vertical distribution of secondary inorganic aerosol (i.e., sulfate, ammonium, and nitrate) is evaluated against a collection of 14 AMS flight campaigns and surface measurements from 2000 to 2010 in the USA and Europe. GISS ModelE2 is used with multiple aerosol microphysics (MATRIX, OMA) and thermodynamic (ISORROPIA II, EQSAM) configurations. Our results show that the MATRIX microphysical scheme improves the model performance for sulfate, but that there is a systematic underestimation of ammonium and nitrate over the USA and Europe in all model configurations. In terms of gaseous precursors, nitric acid concentrations are largely underestimated at the surface while overestimated in the higher levels of the model. Heterogeneous reactions on dust surfaces are an important sink for nitric acid, even high in the troposphere. At high altitudes, nitrate formation is calculated to be ammonia limited. The underestimation of ammonium and nitrate in polluted regions is most likely caused by a too simplified treatment of the NH3 ∕ NH4+ partitioning which affects the HNO3 ∕ NO3− partitioning.
The CAMS interim Reanalysis of Carbon Monoxide, Ozone and Aerosol for 2003–2015
Authors: Flemming J. , Benedetti A. , Inness A. , Engelen R. , Jones L. , Huijnen V. , Remy S. , Parrington M. , Suttie M. , Bozzo A. , Peuch V.-H. , Akritidis D. , Katragkou E.
Published: August 2016

Abstract. A new global reanalysis data set of atmospheric composition (AC) for the period 2003–2015 has been produced by the Copernicus Atmosphere Monitoring Service (CAMS). Satellite observations of total column (TC) carbon monoxide (CO) and aerosol optical depth (AOD) as well as several TC and profile observation of ozone have been assimilated with the Integrated Forecasting System for Composition (C-IFS) of the European Centre for Medium-Range Weather Forecasting. Compared to the previous MACC reanalysis (MACCRA), the new CAMS interim reanalysis (CAMSiRA) is of a coarser horizontal resolution of about 110 km compared to 80 km but covers a longer period with the intent to be continued to present day. This paper compares CAMSiRA against MACCRA and a control experiment (CR) without assimilation of AC retrievals. CAMSiRA has smaller biases than CR with respect to independent observations of CO, AOD and stratospheric ozone. However, ozone at the surface could not be improved by the assimilation. The assimilation of AOD led to a global reduction of sea salt and desert dust as well as an exaggerated increase in sulphate. Compared to MACCRA, CAMSiRA had smaller biases for AOD, surface CO and TC ozone as well as for upper stratospheric and tropospheric ozone. Finally, the temporal consistency of CAMSiRA was clearly better than the one of MACCRA. This was achieved by using a revised emission data set as well as by applying a careful selection and bias-correction of the assimilated retrievals. CAMSiRA is therefore better suited than MACCRA for the study of inter-annual variability than MACCRA as demonstrated for trends in surface CO.
60 years of UK visibility measurements: impact of meteorology and atmospheric pollutants on visibility
Authors: Singh Ajit , Bloss William J. , Pope Francis D.
Published: August 2016

Abstract. Reduced visibility is an indicator of poor air quality. Moreover, degradation in visibility can be hazardous to human safety; for example, low visibility can lead to road, rail, sea and air accidents. In this paper, we explore the combined influence of atmospheric aerosol particle and gas characteristics, and meteorology, on long-term visibility. We use visibility data from eight meteorological stations, situated in the UK, which have been running since the 1950s. The site locations include urban, rural and marine environments. Most stations show a long term trend of increasing visibility which is indicative of reductions in air pollution, especially in urban areas. Additionally, the visibility at all sites show a very clear dependence on relative humidity indicating the importance of aerosol hygroscopicity on the ability of aerosol particles to scatter radiation. The dependence of visibility on other meteorological parameters, such as wind speed and wind direction is also investigated. Most stations show long term increases in temperature which can be ascribed to either climate change, land-use changes (e.g. urban heat island effects) or a combination of both; the observed effect is greatest in urban areas. The impact of this temperature change upon local relative humidity is discussed. To explain the long term visibility trends and their dependence on meteorological conditions, the measured data were fitted to a newly developed light extinction model to generate predictions of historic aerosol and gas scattering and absorbing properties. In general, an excellent fit was achieved between measured and modelled visibility for all 8 sites. The model incorporates parameterizations of aerosol hygroscopicity, particle concentration, particle scattering, and particle and gas absorption. This new model should be applicable and is easily transferrable to other data sets worldwide. Hence, historical visibility data can be used to assess trends in aerosol particle properties. This approach may help constrain global model simulations which attempt to generate aerosol fields for time periods when observational data are scarce or non-existent. Both the measured visibility and the modelled aerosol properties reported in this paper highlight the success of the UK’s Clean Air Act, which was passed in 1956, in cleaning the atmosphere of visibility reducing pollutants.
EnKF and 4D-Var data assimilation with chemical transport model BASCOE (version 05.06)
Authors: Skachko Sergey , Ménard Richard , Errera Quentin , Christophe Yves , Chabrillat Simon
Published: August 2016

Abstract. We compare two optimized chemical data assimilation systems, one based on the ensemble Kalman filter (EnKF) and the other based on four-dimensional variational (4D-Var) data assimilation, using a comprehensive stratospheric chemistry transport model (CTM). This work is an extension of the Belgian Assimilation System for Chemical ObsErvations (BASCOE), initially designed to work with a 4D-Var data assimilation. A strict comparison of both methods in the case of chemical tracer transport was done in a previous study and indicated that both methods provide essentially similar results. In the present work, we assimilate observations of ozone, HCl, HNO3, H2O and N2O from EOS Aura-MLS data into the BASCOE CTM with a full description of stratospheric chemistry. Two new issues related to the use of the full chemistry model with EnKF are taken into account. One issue is a large number of error variance parameters that need to be optimized. We estimate an observation error variance parameter as a function of pressure level for each observed species using the Desroziers method. For comparison purposes, we apply the same estimate procedure in the 4D-Var data assimilation, where both scale factors of the background and observation error covariance matrices are estimated using the Desroziers method. However, in EnKF the background error covariance is modelled using the full chemistry model and a model error term which is tuned using an adjustable parameter. We found that it is adequate to have the same value of this parameter based on the chemical tracer formulation that is applied for all observed species. This is an indication that the main source of model error in chemical transport model is due to the transport. The second issue in EnKF with comprehensive atmospheric chemistry models is the noise in the cross-covariance between species that occurs when species are weakly chemically related at the same location. These errors need to be filtered out in addition to a localization based on distance. The performance of two data assimilation methods was assessed through an 8-month long assimilation of limb sounding observations from EOS Aura MLS. This paper discusses the differences in results and their relation to stratospheric chemical processes. Generally speaking, EnKF and 4D-Var provide results of comparable quality but differ substantially in the presence of model error or observation biases. If the erroneous chemical modelling is associated with moderately fast chemical processes, but whose lifetimes are longer than the model time step, then EnKF performs better, while 4D-Var develops spurious increments in the chemically related species. If, however, the observation biases are significant, then 4D-Var is more robust and is able to reject erroneous observations while EnKF does not.
Feasibility analysis of using inverse modeling for estimating field-scale evapotranspiration in maize and soybean fields from soil water content monitoring networks
Authors: Foolad Foad , Franz Trenton E. , Wang Tiejun , Gibson Justin , Kilic Ayse , Allen Richard G. , Suyker Andrew
Published: August 2016

Abstract. In this study the feasibility of using inverse vadose zone modeling for estimating field scale actual evapotranspiration (ETa) was explored at a long-term agricultural monitoring site in eastern Nebraska. Data from both point scale soil water content sensors (SWC) and the area-average technique of cosmic-ray neutron probes were evaluated against independent ETa estimates from a co-located eddy covariance tower. While this methodology has been successfully used for estimates of groundwater recharge it was critical to assess the performance of other components of the water balance such as ETa. In light of the recent evaluation of Land Surface Model (LSM) performance from the plumber experiment, independent estimates of hydrologic state variables and fluxes are critically needed benchmarks. The results here indicate reasonable estimates of daily and annual ETa from the point sensors but with highly varied soil hydraulic function parameterizations due to local soil texture variability. The results of multiple soil hydraulic parameterizations leading to equally good ETa estimates is consistent with the hydrological principle of equifinality. While this study focused on one particular site the framework can be easily applied to other SWC monitoring networks across the globe. The value added products of groundwater recharge and ETa flux from the SWC monitoring networks will provide additional and more robust benchmarks for the validation of LSM that continue to improve their forecast skill. In addition, the value added products of groundwater recharge and ETa often have more direct impacts on societal decision making than SWC alone. Water flux impacts human decision making from policies on the long-term management of groundwater resources (recharge), to yield forecasts (ETa), and to optimal irrigation scheduling (ETa). Illustrating the societal benefits of SWC monitoring is critical to insure the continued operation and expansion of these public datasets.
Costs of sea dikes – regressions and uncertainty estimates
Authors: Lenk Stephan , Rybski Diego , Heidrich Oliver , Dawson Richard J. , Kropp Jürgen P.
Published: August 2016

Abstract. Failure to consider the costs of adaptation strategies can be seen by decision makers as a barrier for implementing coastal protection measures. In order to validate adaptation strategies to sea-level rise in the form of coastal protection, a consistent and repeatable assessment of the costs is necessary. This paper significantly extends current knowledge on cost estimates by developing, and implementing using real coastal dike data, probabilistic functions of dike costs. With the aim of providing a reproducible estimate of typical sea dike costs and their uncertainty we analyse data from Canada and the Netherlands and relate this to published studies from the US, UK, and Vietnam. We plot the costs divided by dike length as a function of height and test four different regression models. Our analysis shows that a linear function without intercept is sufficient to model the costs, i.e. fixed costs and higher order contributions such as from the volume of core fill material are less significant. We also characterise the spread around the regression models which represents an uncertainty stemming from factors beyond dike length and height. Drawing the analogy to project cost overruns, we employ log-normal distributions and calculate that the range between 3x and x/3 contains 95 % of the data, where x represents the corresponding regression value. We compare our estimates with previously published unit costs for other countries. We note that the unit costs not only depend on the country and land-use (urban/non-urban) of the sites where the dikes are being constructed but also characteristics included in the costs, e.g. property acquisition, utility relocation, project management. We provide recommendations how to improve the reporting and estimating of the costs in order to support future adaptation studies worldwide.
The deep Earth origin of the Iceland plume and its effects on regional
surface uplift and subsidence
Authors: Barnett-Moore N. , Hassan R. , Flament N. , Müller R. D.
Published: August 2016

Abstract. The present-day seismic structure of the mantle under the North Atlantic indicates that the Iceland hotspot represents the surface expression of a deep mantle plume, which is thought to have erupted in the North Atlantic during the Paleocene. The spatial and temporal evolution of the plume since its eruption is still highly debated, and little is known about its deep mantle history. Here, a paleogeographically constrained global mantle flow model is used to investigate the evolution of deep Earth flow and surface dynamic topography in the North Atlantic since the Jurassic. The model shows that over the last ~ 100 Myr a remarkably stable pattern of convergent flow has prevailed in the lowermost mantle near the tip of the African Large Low-Shear Velocity Province (LLSVP), making it an ideal plume nucleation site. The present-day location of the model plume is ~ 10° southeast from the inferred present-day location of the Iceland plume. We apply a constant surface rotation to the model through time, derived from correcting for this offset at present-day. A comparison between the rotated model dynamic topography evolution and available offshore geological and geophysical observations across the region confirms that a widespread episode of Paleocene transient uplift followed by early Eocene anomalous subsidence can be explained by the mantle-driven effects of a plume head ~ 2000 km in diameter, arriving beneath central western Greenland during the Paleocene. The rotated model plume eruption location beneath Western Greenland is compatible with previous models. The mantle flow model underestimates the magnitude of observed anomalous subsidence during the Paleocene in some parts of the North Atlantic by as much as several hundred meters, which we attribute to upper mantle convection processes, not captured by the model.
Perioperative Vision Loss in Spine Surgery and Other Orthopaedic Procedures
Authors: Su Alvin W. , Lin Shuai-Chun , Larson A. Noelle
Published: August 2016

Perioperative vision loss is a rare complication of orthopaedic surgery and has been documented after spine, knee, hip, and shoulder procedures. It is associated with several ophthalmologic diagnoses, most commonly ischemic optic neuropathy. Although the pathophysiology remains unclear, current evidence suggests that systemic hemodynamic compromise and altered balance of intraocular perfusion contribute to the development of ischemic optic neuropathy. Although vision recovery has been reported, the prognosis of perioperative vision loss is poor, and no proven effective treatment is available. Perioperative vision loss is unpredictable and can occur in healthy patients. Associated risk factors include pediatric or elderly age, male sex, obesity, anemia, hypotension or hypertension, perioperative blood loss, prolonged surgical time, and prone positioning. Preventive strategies include avoiding direct pressure to the eye, elevating the head, optimizing perioperative hemodynamic status, and minimizing surgical time with staged surgical procedures as appropriate.