bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Antibacterial Effect and Dimensional Stability of Self-disinfecting Irreversible Hydrocolloid: An in vitro Study
Authors: Benakatti Veena B , Patil Abhijit P , Sajjanar Jayashee , Shetye Supriya S , Amasi Ulhas N , Patil Raghunath
Published: October 2017

Aim

This study evaluated the antibacterial activity and dimensional stability of irreversible hydrocolloids mixed with different concentrations of chlorhexidine gluconate instead of water.

Materials and methods

Experimental specimens (45 specimens) were prepared and allocated into three groups of 15 each. Group I: Impression material mixed with distilled water served as control. Groups II and III were prepared with 0.12 and 0.2% chlorhexidine gluconate solution, respectively. Specimens in each group were subjected to tests for dimensional stability. For antimicrobial activity, 30 specimens were prepared and allocated into three groups of 10 each named as group I (control), group II (0.12% chlorhexidine gluconate), and group III (0.2% chlorhexidine gluconate) similar to specimens for dimensional stability. Statistical analysis was performed using a one-way analysis of variance (ANOVA) and Tukey test.

Results

Zones of inhibition were observed around test specimens, but not around control specimens; there was a significant intergroup difference in the diameters of the inhibition zones. In the test for dimensional stability, no significant differences were detected among groups, and the accuracy was clinically acceptable.

Conclusion

Irreversible hydrocolloid impression material mixed with chlorhexidine exhibits varying degrees of antibacterial activity without influencing the dimensional stability of set material.

Clinical significance

Many contagious diseases can be prevented by practical control of infection in the dental office. Chlorhexidine gluconate, as a mixing liquid, ensures disinfection of impression, and this method of disinfection is more convenient and avoids extra effort as in other disinfection techniques.

How to cite this article

Benakatti VB, Patil AP, Sajjanar J, Shetye SS, Amasi UN, Patil R. Evaluation of Antibacterial Effect and Dimensional Stability of Self-disinfecting Irreversible Hydrocolloid: An in vitro Study. J Contemp Dent Pract 2017;18(10):887-892.
Mechanical and Physical Properties of Two Different Resin-based Materials: A Comparative Study
Authors: Alturki Basem N , Albishi Wjoud W , Alsadi Fahad M , El-Tubaigy Khaled M
Published: October 2017

Aim

The purpose of this study was to evaluate the degree of conversion (DC) of two different resin-based composite materials (nanofill composite and ormocer) and correlate it with some mechanical properties of these two restorative materials.

Materials and methods

Two different resin-based materials (Filtek Supreme XT and Admira) were tested. A total of 30 samples of each type of selected composite were prepared. Specimens were immersed in distilled water for 24 hours. Then, the specimens were subjected to DC, hardness, and diametral tensile strength (DTS) measurements. The data obtained were tabulated for statistical analysis. The t-test was used to detect the significant difference among the variables tested in this study. Furthermore, the interrelationship between the studied parameters was investigated using a simple correlation coefficient statistical test.

Results

Statistically significant differences were observed regarding DC, hardness, and DTS. Filtek Supreme XT presented the highest values. There was a positive correlation between DC and hardness. Also there was a correlation between DC and DTS, but it was not significant.

Conclusion

Under the tested experimental conditions, the DC of Filtek Supreme XT was higher than that of Accordingly, Filtek Supreme XT showed better mechanical properties.

Clinical significance

Filtek Supreme XT showed superior mechanical properties. Therefore, orthodontic bracket-based composite combinations may also be expected to perform well clinically over the lifetime of a bonded orthodontic appliance.

How to cite this article

Baeshen H, Alturki BN, Albishi WW, Alsadi FM, El-Tubaigy KM. Mechanical and Physical Properties of Two Different Resin-based Materials: A Comparative Study. J Contemp Dent Pract 2017;18(10):905-910.
Comparison of Hypersensitivity in Metal Ceramic Crowns cemented with Zinc Phosphate and Self-adhesive Resin: A Prospective Study
Authors: Garhnayak Mirna , Dhal Angurbala , Garhnayak Lokanath , Kar Aswini K , Shankar Thatapudi
Published: October 2017

Background

Luting agents used to fix artificial prostheses, such as fixed partial denture (FPD) to tooth are basically viscous in nature and show chemical reaction for fixation. Postcementation hypersensitivity is a frequent complaint of patients. The present study was conducted to compare postcementation hypersensitivity with zinc phosphate and self-adhesive resin in complete coverage crown.

Materials and methods

This study included 30 patients in which 60 porcelein fused to metal crowns was placed. Two metal crowns were placed in each patient in nonantagonistic contralateral quadrants. First crown was cemented with zinc phosphate cement, while the other was cemented with self-adhesive resin. Hypersensitivity was evaluated by visual analog scale (VAS) score and by clinical test. For clinical evaluation of sensitivity, hot and cold water was applied to the cervical margin of restoration for 5 seconds and response was recorded.

Results

This study consisted of 30 patients in which 60 crowns were given. There was no statistical difference in VAS score of mastication in zinc phosphate cement recorded at baseline, 1 week, 4 weeks, 6 months, 1 year, and 2 years (p > 0.05). Cold response also did not show a significant difference at six time points. Warm response showed slight decrease in subsequent time points but was nonsignificant (p > 0.05). Similarly, with selfadhesive resin cement, VAS score during mastication, hot and cold response was statistically nonsignificant (p > 0.05).

Conclusion

Postcementation hypersensitivity is a frequent complaint that patient may experience. However, we found no statistically significant difference in both cements tested.

Clinical significance

Postcementation hypersensitivity is an unpleasant sensation experienced by patients. This may affect the success of any prosthesis. Thus, selection of luting agent for cementation plays an important role to eliminate this symptom.

How to cite this article

Shankar T, Garhnayak M, Garhnayak L, Dhal A, Kar AK. Comparison of Hypersensitivity in Metal Ceramic Crowns cemented with Zinc Phosphate and Selfadhesive Resin: A Prospective Study. J Contemp Dent Pract 2017;18(10):923-926.
Post-insertion Posterior Single-implant Occlusion Changes at Different Intervals: A T-Scan Computerized Occlusal Analysis
Authors: Madani Azam S , Nakhaei Mohammadreza , Alami Malihe , Haghi Hamidreza Rajati , Moazzami Saied Mostafa
Published: October 2017

Aim

The aim of this prospective cohort study was to evaluate the postinsertion posterior single-implant occlusion changes at 3- and 6-month intervals using T-Scan computerized occlusal analysis.

Materials and methods

A total of 21 patients received single implant, opposed by natural dentition, in posterior regions of the maxilla or mandible (13 premolar, 8 molar) and were finally restored with cemented-retained metal–ceramic crowns. The occlusal contacts were equilibrated according to the implantprotective occlusion concept to develop light contact with heavy occlusion and no contact with light occlusion in maximum intercuspation. The percentage of force applied to the implant crowns (POFI) and contralateral teeth (POFT) was evaluated using T-Scan computerized occlusal analysis at prosthesis insertion, 3- and 6-month follow-up appointments. The data were statistically analyzed using Friedman test and Wilcoxonpost hoctest (α = 0.05).

Results

The POFI values at the 6- and 3-month follow-up appointments were significantly higher than those at prostheses insertion (p = 0.001 and p = 0.005 respectively). In addition, there were significant differences between the POFI at 3- and 6-month follow-up (p = 0.020). However, the POFT values at 3- and 6-month follow-up appointments were significantly lower than those at baseline (p<0.001).

Conclusion

The intensity of occlusal contacts of implantsupported prostheses opposed by natural dentition increased after prosthesis insertion. Placement of single posterior implant-supported restoration decreased the percentage of occlusal force applied to contralateral arch.

Clinical significance

A periodic occlusal adjustment of implant-supported prostheses is necessary to prevent potential overloading from the movement of opposing natural dentition.

How to cite this article

Madani AS, Nakhaei M, Alami M, Haghi HR, Moazzami SM. Post-insertion Posterior Singleimplant Occlusion Changes at Different Intervals: A T-Scan Computerized Occlusal Analysis. J Contemp Dent Pract 2017;18(10):927-932.
Characteristic of Malocclusion among Saudi Special Need Group Children
Authors: Alkhadra Thamer
Published: October 2017

Introduction

The present study analyzed the characteristics of malocclusions, occlusal traits among Special Health care Needs (SHCN) children with Down syndrome (DS) and autism disorder (AD) in Riyadh City, Kingdom of Saudi Arabia.

Materials and methods

A total of 100 DS and 100 AD children from five rehabilitation centers in and around Riyadh, Kingdom of Saudi Arabia, were included in the study. Any children with history of ongoing medical treatment, extraction, or orthodontic treatment were excluded from the study. Out of the 200 patients examined, 131 were males and 69 were females and the age of the children ranged from 6 to 14 years. The children were examined for malocclusion characteristics using the Angle's classification of malocclusion, and also other occlusal traits, such as overjet, overbite, cross bite, and open bite were also determined. The data obtained were analyzed using Statistical Package for the Social Sciences, version 16 to generate descriptive statistics for each variable.

Results

The analyzed data of the right and left permanent molar relation showed higher incidence of class III malocclusion (66%) in DS children as compared with (3–4%) AD children. The AD children presented with higher percentage of class I malocclusion (40–41%) as compared with (10–14%) DS children. During examination of the primary molars, the analyzed data showed that left primary molar had more mesial shift in AD children as compared with DS children.

Conclusion

Down syndrome children had high incidence of class III malocclusion and autistic children had high incidence of class I malocclusion. Overall, the DS children were more prone to malocclusion.

Clinical significance

This study provides database for health professionals in Saudi Arabia in regard to malocclusion of autistics and DS patients.

How to cite this article

Alkhadra T. Characteristic of Malocclusion among Saudi Special Need Group Children. J Contemp Dent Pract 2017;18(10):959-963.
Knowledge, Attitude, and Practices regarding Pharmacovigilance and Adverse Drug Reaction reporting among Dental Students in a Teaching Hospital, Jodhpur, India: A Cross-sectional Study
Authors: Sharma Ashish , Chhabra Kumar G , Chhabra Chaya , Reddy J Jyothirmai , Deolia Shravani G , Mittal Yogesh
Published: October 2017

Introduction

This is a cross-sectional knowledge, attitude, and practices (KAPs) study on pharmacovigilance (PV) and adverse drug reaction (ADR) reporting among dental students in a teaching hospital in India.

Aim

The aim of this study was to assess the KAP of dental students regarding PV, ADR reporting, and barriers toward the same.

Materials and methods

A cross-sectional survey using a selfadministered, investigator-developed, close-ended questionnaire was conducted in an academic dental hospital in India. All prescribers including third year students, final year students, and house surgeons of the same institute were included for assessment of KAP regarding PV using 16, 8, and 8 items respectively. Data regarding barriers toward ADR reporting and demographics were also collected. Mann–Whitney U-test and Kruskal–Wallis test were applied followed by post hoc test.

Results

A total of 241 of 275 respondents participated in the study with a response rate of 87.5%. Overall, 64% reported that they had no idea about the term PV. Age was significantly associated with knowledge (p = 0.045) and attitude (p = 0.016). Barriers contributing to underreporting were difficulty in deciding whether or not an ADR has occurred (52.0%), concerns that the report may be wrong (37%), lack of confidence to discuss ADR with colleagues (29%), and almost no financial benefits (24%).

Conclusion

Participants had a comparatively favorable attitude toward PV, but their knowledge and practice need considerable improvements. This study highlights the need for appropriate dental curriculum changes and further multicentric studies to shed more light on important issues of PV among dentists in India.

Clinical significance

This study explores dentists’ knowledge, attitude, and behavior regarding PV, which could help to improve patient's safety and care. The favorable attitude of dentists is an indication that PV could be added in depth in the curriculum and in general practice. Information on barriers for reporting the ADRs could help to find possible solutions for removing the barriers precisely.

How to cite this article

Chhabra KG, Sharma A, Chhabra C, Reddy JJ, Deolia SG, Mittal Y. Knowledge, Attitude, and Practices regarding Pharmacovigilance and Adverse Drug Reaction reporting among Dental Students in a Teaching Hospital, Jodhpur, India: A Cross-sectional Study. J Contemp Dent Pract 2017;18(10):964-969.
Negotiating Learning and Identity in Higher Education
Authors: Bangeni Bongi , Kapp Rochelle
Published: October 2017

While access to higher education has increased globally, student retention has become a major challenge. This book analyses various aspects of the learning pathways of black students from a range of disciplinary backgrounds at a relatively elite, English-medium, historically white South African university. The students are part of a generation of young black people who have grown up in the new South Africa and are gaining access to higher education in unprecedented numbers. Based on two longitudinal case studies, Negotiating Learning and Identity in Higher Education makes a contribution to the debates about how to facilitate access and graduation of working-class students. The longitudinal perspective enabled the students participating in the research to reflect on their transition to university and the stumbling blocks they encountered in their senior years. The contributors show that the school-to-university transition is not linear or universal. Students had to negotiate multiple transitions at various times and both resist and absorb institutional, disciplinary and home discourses.

The book describes and analyses the students' ambivalence as they straddle often conflicting discourses within their disciplines; within the institution; between home and the institution; and as they occupy multiple subject positions that are related to the boundaries of place and time. Each chapter also describes the ways in which the institution supports and/or hinders students' progress, explores the implications of its findings for models of support and addresses the issue of what constitutes meaningful access to institutional and disciplinary discourses
Bare Architecture: A Schizoanalysis
Authors: Smith Chris L.
Published: October 2017

Bare Architecture: a schizoanalysis, is a poststructural exploration of the interface between architecture and the body. Chris L. Smith skilfully introduces and explains numerous concepts drawn from poststructural philosophy to explore the manner by which the architecture/body relation may be rethought in the 21st century. Multiple well-known figures in the discourses of poststructuralism are invoked: Gilles Deleuze and Félix Guattari, Roland Barthes, Georges Bataille, Maurice Blanchot, Jorges Luis Borges and Michel Serres. These figures bring into view the philosophical frame in which the body is formulated.

Alongside the philosophy, the architecture that Smith comes to refer to as ‘bare architecture’ is explored. Smith considers architecture as a complex construction and the book draws upon literature, art and music, to provide a critique of the limits, extents and opportunities for architecture itself. The book considers key works from the architects Douglas Darden, Georges Pingusson, Lacatan and Vassal, Carlo Scarpa, Peter Zumthor, Marco Casagrande and Sami Rintala and Raumlabor. Such works are engaged for their capacities to foster a rethinking of the relation between architecture and the body.
A PROTEÇÃO POSITIVA DO DOMÍNIO PÚBLICO
Authors: Marinho Maria Edelvacy Pinto
Published: October 2017

A expansão da proteção dos bens intelectuais não se dirige apenas à natureza do objeto passível de proteção, mas também aos direitos de exploração concedidos aos seus titulares. O artigo analisa, a partir dos instrumentos jurídicos internacionais, o espaço destinado à proteção do domínio público. Parte-se do pressuposto de que um ambiente favorável ao desenvolvimento da inovação consiste na busca do equilíbrio entre proteção e acesso aos bens intelectuais. O exame realizado nesse artigo é feito tendo como referência o direito de patentes e a partir da pesquisa documental e bibliográfica. Conclui-se que o foco demasiado na proteção dos bens intelectuais das últimas décadas tem alterado o equilíbrio necessário para o estímulo a inovação e que é necessário discutir mecanismos eficientes de proteção positiva do domínio público e não apenas a proteção por exclusão do sistema de patentes, como tem sido feito até então.
POLÍTICAS PÚBLICAS E ESCOLHA RACIONAL: O CASO DO CENTRO URBANO DE CULTURA, ARTE, CIÊNCIA E ESPORTE DE FORTALEZA, ESTADO DO CEARÁ
Authors: De Andrade Mariana Dionísio , Remígio Rodrigo Ferraz de Castro
Published: October 2017

O objetivo do presente artigo consiste em responder a seguinte pergunta: por que determinadas políticas públicas ingressam na agenda política e permanecem na modalidade incremental, apesar das mudanças na gestão governamental? Parte-se da ideia que a construção de determinadas fases do ciclo de políticas públicas ocorre em razão da correspondência ótima entre meios e fins, momento no qual atores políticos utilizam estratégias para a maximização de benefícios. A pesquisa possui abordagem qualitativa e se apoia em revisão de literatura. O método é observacional processual causal, com base no caso do Centro Urbano de Cultura, Arte, Ciência e Esporte de Fortaleza – CUCA, como exemplo de política pública que foi replicada por outra gestão municipal. A seleção dos casos observados foi realizada com base na incidência da política, com periodização compreendida entre 2009 a 2015. Conclui-se que há relação subjacente entre a manutenção da política e a maximização de benefícios, e que a política pública analisada teve continuidade na cidade de Fortaleza não apenas em razão dos resultados, mas também pelos compromissos contratuais assumidos entre a prefeitura municipal e o Banco Interamericano de Desenvolvimento, evidenciando uma inclinação maior às estratégias políticas que à atenção às demandas de ordem social.
A REGULARIZAÇÃO FUNDIÁRIA URBANA E RURAL: NECESSIDADE DE MARCOS TEÓRICOS E DE POLÍTICAS PÚBLICAS DISTINTOS
Authors: Reis Émilien Vilas Boas , Oliveira Márcio Luís de
Published: October 2017

Independentemente das matrizes filosóficas liberais ou comunitárias, que justificam tanto a propriedade e a posse públicas e/ou privadas, a ocupação imobiliária urbana ou rural irregulares necessitam de regularização fundiária para viabilizar o direito fundamental e direito humano de acesso à moradia e ao uso social da terra produtiva, respectivamente. Como se tratam de realidades e problemas distintos, seria, porém, adequada a adoção de marcos legais e de políticas públicas específicas para a regularização fundiária urbana e a rural. A primeira tem por foco a legalização e a inserção da propriedade e da posse na estrutura regular das cidades. A segunda, tem por objetivo a legalização e a inserção da propriedade e da posse na estrutura de produção no campo. Ambas as regularizações visam à efetividade do direito à moradia social e ambientalmente sustentáveis. No caso da regularização fundiária rural, acresce-se, ainda, o direito de uso da terra como política de equidade socioeconômica e de produção sustentável. Na elaboração do artigo foi adotada a metodologia histórico-analítica para reconstruir o pensamento filosófico sobre a propriedade e a posse e o método conceitual-analítico para tratar da regularização fundiária urbana e rural em suas premissas conceituais e procedimentais. Não se fez, neste trabalho, o uso da dogmática jurídica de modo mais específico, uma vez que seu objetivo principal foi a abordagem filosófico-conceitual do tema. Nesse sentido, e em razão do viés analítico a que foi dado ao tema-problema, não se adotou um marco teórico específico.
The Absorption Ångström Exponent of black carbon:
from numerical aspects
Authors: Liu Chao , Chul Chul Eddy , Yin Yan
Published: October 2017

Abstract. The Absorption Ångström Exponent (AAE) is an important aerosol optical parameter used for aerosol characterization and apportionment studies. The AAE of black carbon (BC) is widely accepted to be 1.0, although observational estimates give a quite wide range of 0.6~1.1. With considerable uncertainties related to observations, a numerical study is a powerful method, if not the only one, to provide a better and more accurate understanding on BC AAE. This study calculates BC AAE using realistic particle geometries based on fractal aggregate and an accurate numerical optical model (namely the Multiple-Sphere T-Matrix method). At odds with the expectations, BC AAE is not 1.0, even when BC is assumed to have small sizes and a wavelength independent refractive index. With a wavelength independent refractive index, the AAE of fresh BC is approximately 1.05, and is quite insensitive to particle size distribution. BC AAE goes lower when BC particles are aged (compact structures or coated by other scattering materials). For coated BC, we prescribed the coating thickness distribution based on a published experimental study, where smaller BC cores were shown to develop thicker coating than bigger BC cores. Both Compact and Coated BC the AAE ranges, at realistic particle sizes. For both Compact and Coated BC, the AAE is highly sensitive to particle size distribution, ranging from approximately 0.8 to 1.0 for relatively large BC with wavelength-independent refractive index. When the refractive index is allowed to vary with wavelength, a feature with observational backing, the BC AAE shows a much wider range. We propose that the presented results herein serve as a comprehensive guide for the response of BC AAE to BC size, refractive index, and geometry.
Multiphase Reaction of SO2 with NO2 on CaCO3 Particles. 2. NO2-initialized Oxidation of SO2 by O2
Authors: Yu Ting , Zhao Defeng , Song Xiaojuan , Zhu Tong
Published: October 2017

Abstract. The reaction of SO2 with NO2 on the surface of aerosol particles has been suggested to be important in sulfate formation during severe air pollution in China. However, we found that the direct oxidation of SO2 by NO2 was slow and might not be the main reason for sulfate formation in ambient air. In this study, we investigated the multiphase reaction of SO2 with NO2 on single CaCO3 particles in synthetic air, i.e., in the presence of O2, using Micro-Raman spectroscopy. The reaction converted the CaCO3 particle to the Ca(NO3)2 droplet containing CaSO4 × 2H2O solid particles embedded in it, which constituted a large fraction of the droplet volume at the end of the reaction. Compared with the reaction in the absence of O2, the morphology of the particle during the reaction in synthetic air was significantly different and the amount of sulfate formed at the end of the experiment was much higher. The reactive uptake coefficient of SO2 for sulfate formation was on the order of 10−5, which was two to three orders of magnitude higher than that in the absence of O2. According to the difference between the reactive uptake coefficient of SO2 in the absence of O2 and that in the presence of O2, we found that in the multiphase reaction of SO2 with NO2 in synthetic air, O2 was the main oxidant of SO2 and necessary for radical chain propagation. NO2 acted as the initializer of the radical formation but not the main oxidant. Such synergy of NO2 and O2 resulted in much faster sulfate formation than when either of them was absent. We estimated that the multiphase oxidation of SO2 by O2 in the presence of NO2 can be an important source of sulfate and sink of SO2 based on the calculated lifetime of SO2 regarding the loss by the multiphase reaction versus the lifetime regarding the loss by the gas phase reaction with OH radical. Parameterizing the reactive uptake coefficient of the reaction observed in our laboratory for further model simulation is needed, as well as an integrated assessment based on field observation, laboratory study results, and model simulation to evaluate the importance of the reaction in ambient air during the severe air pollution period, especially in China.
An electrospray chemical ionization source for real-time measurement of atmospheric organic and inorganic vapors
Authors: Zhao Yue , Chan Jeremy K. , Lopez-Hilfiker Felipe D. , McKeown Megan A. , D'Ambro Emma L. , Slowik Jay G. , Riffell Jeffrey A. , Thornton Joel A.
Published: October 2017

Abstract. We present an electrospray ion source coupled to an orthogonal continuous-flow atmospheric pressure chemical ionization region. The source can generate intense and stable currents of several specific reagent ions using a range of salt solutions prepared in methanol, thereby providing both an alternative to more common radioactive ion sources and allowing for the generation of reagent ions that are not available in current chemical ionization mass spectrometry (CIMS) techniques, such as alkaline cations. We couple the orthogonal electrospray chemical ionization (ESCI) source to a high-resolution time-of-flight mass spectrometer (HR-ToF-MS), and assess instrument performance through calibrations using nitric acid (HNO3), formic acid (HCOOH), and isoprene epoxydiol (trans-β-IEPOX) gas standards, and through measurements of oxidized organic compounds formed from ozonolysis of α-pinene in a continuous-flow reaction chamber. When using iodide as the reagent ion, the HR-ToF-ESCIMS prototype has a sensitivity of 11, 2.4, and 10 cps pptv−1 per million counts per second (cps) of reagent ions and a detection limit (3σ, 5 s averaging) of 4.9, 12.5, and 1.4 pptv to HNO3, HCOOH, and IEPOX, respectively. These values are comparable to those obtained using an iodide-adduct HR-ToF-CIMS with a radioactive ion source and low-pressure ion–molecule reaction region. Applications to the α-pinene ozonolysis system demonstrates that HR-ToF-ESCIMS can generate multiple reagent ions (e.g., I−, NO3−, acetate, Li+, Na+, K+, and NH4+) having different selectivity to provide a comprehensive molecular description of a complex organic system.
A new photometric ozone reference in the Huggins bands: the absolute ozone absorption cross section at the 325 nm HeCd laser wavelength
Authors: Janssen Christof , Elandaloussi Hadj , Gröbner Julian
Published: October 2017

Abstract. The room temperature (294.09 K) absorption cross section of ozone at the 325 nm HeCd wavelength has been determined under careful consideration of possible biases. At the vacuum wavelength of 325.126 nm, thus in a region used by a variety of ozone remote sensing techniques, an absorption cross section value of σ = 16.470 · 10−21 cm2 was measured. The measurement provides the currently most accurate direct photometric absorption value of ozone in the UV with an expanded (coverage factor k = 2) uncertainty u(σ) = 31 · 10−24 cm2, corresponding to a relative level of two per mil. The measurements are most compatible with a relative temperature coefficient cT = (1 / σ) dσ / dT = 0.0031 K−1 at 294 K. The cross section and its uncertainty value have been obtained from a generalised linear regression with correlated uncertainties. It will serve as a reference for ozone absorption spectra required for the long-term remote sensing of atmospheric ozone in the Huggins bands. The comparison with commonly used absorption cross section data sets for remote sensing reveals a possible bias of about 2 %. This could partly explain a 4 % discrepancy between UV and IR remote sensing data and indicates that further studies will be required to reach the accuracy goal of 1 % in atmospheric reference spectra.
Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties
Authors: Richardson Mark , Stephens Graeme L.
Published: October 2017

Abstract. An information content analysis is used to select channels for a marine liquid cloud retrieval using the high-spectral-resolution oxygen A-band instrument on NASA’s Orbiting Carbon Observatory-2 (OCO-2). Desired retrieval properties are cloud optical depth, cloud pressure thickness and cloud-top pressure and the optimal channels depend on the atmospheric state, cloud properties and position within the OCO-2 swath. Based on information content criteria we select a micro-window of 75 of the 853 functioning OCO-2 channels spanning 763.5–764.6 nm and perform a series of synthetic retrievals with perturbed initial conditions. We estimate posterior errors from the sample standard deviations and obtain ±0.75 in optical depth, ±12.9 hPa in both cloud-top pressure and cloud pressure thickness, although removing the 10 % of samples with the highest χ2 reduces posterior error in cloud-top pressure to ±2.9 hPa and cloud pressure thickness to ±2.5 hPa. The application of this retrieval to real OCO-2 measurements is briefly discussed, along with limitations and the greatest caution is urged regarding the assumption of a single homogeneous cloud layer, which is often, but not always, a reasonable approximation for marine boundary layer clouds.
Catchment tracers reveal discharge, recharge and sources of groundwater-borne pollutants in a novel lake modelling approach
Authors: Kristensen Emil , Madsen-Østerbye Mikkel , Massicotte Philippe , Pedersen Ole , Markager Stiig , Kragh Theis
Published: October 2017

Abstract. Groundwater borne contaminants such as e.g., nutrients, dissolved organic carbon (DOC), coloured dissolved organic matter (CDOM) and pesticides impact the biological quality of lakes. The sources of pollution can, however, be difficult to identify due to high heterogeneity in groundwater flow patterns. This study presents a novel approach for fast hydrological surveys of small groundwater-fed lakes using multiple groundwater-borne tracers. Water samples were collected from groundwater wells installed every 50 m within 5–45 m from the shore and were analysed for tracer concentrations of CDOM, DOC, total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), 𝛿18O isotopes and fluorescent dissolved organic matter (FDOM) components derived from parallel factor analysis (PARAFAC). Based on tracer concentrations and degradation rates, the maximum WRT was estimated to 2 years. Isolation of groundwater recharge areas were based on 𝛿18O measurements and sites with high a degree of recharge was isolated using PARAFAC component C4. Groundwater discharge sites and the fractions of water delivered from the sites were isolated with the Community Assembly via Trait Selection model (CATS) for WRTs between 0.25 and 2 years. The identified recharge sites corresponded to areas adjacent to drainage channels and a cluster analysis of component C4 further identified five sites which showed a tendency of high groundwater recharge rates. Isolated groundwater discharge sites were located in the eastern part of the lake and a single site in the southern part. Observations from the eastern part of the lake revealed an impermeable clay layer that promotes discharge during short precipitation events, which would be difficult to identify using traditional hydrological methods. High tracer concentrations in the southern part in relation to lake concentrations showed that only a smaller fraction of water could originate from this area, thereby confirming the model results. The methodology used can be applied to smaller lakes yielding results within a short time frame with information related to the WRT of the lake.
Stable isotopes of nitrate reveal different nitrogen processing
mechanisms in streams across a land use gradient during wet and dry
periods
Authors: Wong Wei Wen , Pottage Jesse , Warry Fiona Y. , Reich Paul , Roberts Keryn L. , Grace Michael R. , Cook Perran L. M.
Published: October 2017

Abstract. Understanding the relationship between land use and the dynamics of nitrate (NO3−) is the key to constrain sources of NO3− export in order to aid effective management of waterways. In this study, isotopic compositions of NO3− (δ15N-NO3− and δ18O-NO3−) were used to elucidate the effects of land use (agriculture in particular) and rainfall on the major sources and sinks of NO3− within the Westernport catchment, Victoria, Australia. This study is one of the very few studies carried out in temperate regions with highly stochastic rainfall patterns; enabling a more comprehensive understanding of the applications of NO3− isotopes in catchment ecosystems with different climatic conditions. Longitudinal samples were collected from five streams with different agriculture land use intensities on five occasions – three during dry periods and two during wet periods. At the catchment scale, we observed significant positive relationships between NO3− concentrations, δ15N-NO3− and percentage agriculture reflecting the dominance of anthropogenic nitrogen inputs within the catchment. Different rainfall conditions appeared to be major controls on the predominance of the sources and transformation processes of NO3− in our study sites. Artificial fertiliser was the dominant source of NO3− during the wet periods while nitrified organic matter in sediment and nitrified manure were more apparent sources of NO3− to the surface water during the dry periods. Denitrification was prevalent during the wet periods while uptake of NO3− by plants or algae was only observed during the dry periods in two streams. The outcome of this study suggests that effective reduction of NO3− load to the streams can only be achieved by prioritising management strategies based on different rainfall conditions.
Particulate barium tracing significant mesopelagic carbon remineralisation in the North Atlantic
Authors: Lemaitre Nolwenn , Planquette Hélène , Planchon Frédéric , Sarthou Géraldine , Jacquet Stéphanie , García-Ibáñez Maribel I. , Gourain Arthur , Cheize Marie , Monin Laurence , André Luc , Laha Priya , Terryn Herman , Dehairs Frank
Published: October 2017

Abstract. The remineralisation of sinking particles by prokaryotic heterotrophic activities is important for controlling oceanic carbon sequestration. Here, we report mesopelagic particulate organic carbon (POC) remineralisation fluxes in the North Atlantic along the GEOTRACES-GA01 section (GEOVIDE cruise; May–June 2014) using the particulate biogenic barium (excess barium; Baxs) proxy. Important mesopelagic (100–1000 m) Baxs differences were observed along the transect depending on the intensity of past blooms, the phytoplankton community structure and the physical forcing, including downwelling. The subpolar province was characterized by the highest mesopelagic Baxs content (up to 727 pmol L−1), which was attributed to an intense bloom averaging 6 mg Chl-a m−3 between January and June 2014 and by an intense 1500 m-deep convection in the central Labrador Sea during the winter preceding the sampling. This downwelling could have promoted a deepening of the prokaryotic heterotrophic activity, increasing the Baxs content. In comparison, the temperate province, characterized by the lowest Baxs content (391 pmol L−1), was sampled during the bloom period and phytoplankton appear to be dominated by small and calcifying species, such as coccolithophorids. The Baxs content, related to an oxygen consumption, was converted into a remineralisation flux using an updated relationship, proposed for the first time in the North Atlantic. The estimated fluxes were in the same order of magnitude than other fluxes obtained by independent methods (moored sediment traps, incubations) in the North Atlantic. Interestingly, in the subpolar and subtropical provinces, mesopelagic POC remineralisation fluxes (up to 13 and 4.6 mmol C m−2 d−1, respectively) were equalling and occasionally even exceeding upper ocean POC export fluxes, highlighting the important impact of the mesopelagic remineralisation on the biological carbon pump with a near-zero, deep (> 1000 m) carbon sequestration efficiency in spring 2014.
Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand
Authors: Browne Imogen M. , Moy Christopher M. , Riesselman Christina R. , Neil Helen L. , Curtin Lorelei G. , Gorman Andrew R. , Wilson Gary S.
Published: October 2017

Abstract. The Southern Hemisphere westerly winds (SHWWs) play a major role in controlling wind-driven upwelling of Circumpolar Deep Water (CDW) and outgassing of CO2 in the Southern Ocean, on interannual to glacial–interglacial timescales. Despite their significance in the global carbon cycle, our understanding of millennial- and centennial-scale changes in the strength and latitudinal position of the westerlies during the Holocene (especially since 5000 yr BP) is limited by a scarcity of palaeoclimate records from comparable latitudes. Here, we reconstruct middle to late Holocene SHWW variability using a fjord sediment core collected from the subantarctic Auckland Islands (51° S, 166° E), located in the modern centre of the westerly wind belt. Changes in drainage basin response to variability in the strength of the SHWW at this latitude are interpreted from downcore variations in magnetic susceptibility (MS) and bulk organic δ13C and atomic C ∕ N, which monitor influxes of lithogenous and terrestrial vs. marine organic matter, respectively. The fjord water column response to SHWW variability is evaluated using benthic foraminifer δ18O and δ13C, both of which are influenced by the isotopic composition of shelf water masses entering the fjord. Using these data, we provide marine and terrestrial-based evidence for increased wind strength from  ∼  1600 to 900 yr BP at subantarctic latitudes that is broadly consistent with previous studies of climate-driven vegetation change at the Auckland Islands. Comparison with a SHWW reconstruction using similar proxies from Fiordland suggests a northward migration of the SHWW over New Zealand during the first half of the last millennium. Comparison with palaeoclimate and palaeoceanographic records from southern South America and West Antarctica indicates a late Holocene strengthening of the SHWW after  ∼  1600 yr BP that appears to be broadly symmetrical across the Pacific Basin. Contemporaneous increases in SHWW at localities on either side of the Pacific in the late Holocene are likely controlled atmospheric teleconnections between the low and high latitudes, and by variability in the Southern Annular Mode and El Niño–Southern Oscillation.
Methoxy aromatic acids in an Arctic ice core from Svalbard: a
proxy record of biomass burning
Authors: Grieman Mackenzie M. , Aydin Murat , Isaksson Elisabeth , Schwikowski Margit , Saltzman Eric S.
Published: October 2017

Abstract. This study presents vanillic acid and para-hydroxybenzoic acid levels in an Arctic ice core from Lomonosovfonna, Svalbard covering the past 800 years. These methoxy aromatic acids are likely derived from lignin combustion in wildfires and long-range aerosol transport. Vanillic and para-hydroxybenzoic acid are present throughout the ice core, confirming that these compounds are preserved on millennial time scales. Vanillic and para-hydroxybenzoic acid concentrations in the Lomonosovfonna ice core ranged from below the limits of detection to 0.2 and 0.07 ppb, respectively (1 ppb = 1000 ng/l). Vanillic acid levels are high (below the limit of detection to 0.1 ppb) from 1200–1400 CE, then gradually decline into the 20th century. The largest peak in the vanillic acid in the record occurs from 2000–2008 CE. In the para-hydrobenzoic acid record, there are three centennial-scale peaks around 1300, 1550, and 1650 CE superimposed on a long-term decline in the baseline levels throughout the record. Air mass back trajectory analysis indicates that Siberia and Europe are the primary source regions for wildfire emissions reaching the Lomonosovfonna site. The Lomonosovfonna data are similar to those from the Eurasian Arctic Akademii Nauk ice core during the early part of the record (1220–1400 CE), but the two ice cores diverge markedly after 1400 CE. This coincides with a shift in North Atlantic climate marked by a change of the North Atlantic Oscillation from a positive to a more negative state.
BEATBOX: Background Error Analysis Testbed with Box Models
Authors: Knote Christoph , Barré Jérôme , Eckl Max
Published: October 2017

Abstract. The Background Error Analysis Testbed (BEATBOX) is a new data assimilation framework for box models. Based on the BOX Model eXtension (BOXMOX) to the Kinetic Pre-Processor (KPP), this framework allows to conduct performance evaluations of data assimilation experiments, sensitivity analyses and detailed chemical scheme diagnostics from an Observation Simulation System Experiment (OSSE) point of view. The BEATBOX framework incorporates an observation simulator and a data assimilation system with the possibility of choosing ensemble, adjoint or combined sensitivities. A user-friendly, python-based interface allows tuning of many parameters for atmospheric chemistry and data assimilation research as well as for educational purposes, e.g. observations error, model covariances, ensemble size, perturbation distribution on initial conditions, and so on. In this work, the testbed is described and two case studies are presented to illustrate: the design of a typical OSSE experiment, data assimilation experiments, a sensitivity analysis and a method for diagnosing model errors. BEATBOX is released as an open source tool for the atmospheric chemistry and data assimilation communities.
Technical Note: False low turbidity readings during high suspendedsediment concentrations
Authors: Voichick Nicholas , Topping David J. , Griffiths Ronald E.
Published: October 2017

Abstract. Turbidity, a measure of water clarity, is monitored for a variety of purposes including: 1) to help determine whether water is safe to drink; 2) to establish background conditions of lakes and rivers and detect pollution caused by construction projects and storm water discharge; and 3) to establish connections with aquatic biological properties, such as primary production and predator-prey interactions. Turbidity is normally measured with an optical probe that detects light scattered from particles in the water. Probes have defined upper limits of the range of turbidity that they can measure. The general assumption is that when turbidity exceeds this upper limit, the values of turbidity will be constant, i.e., the probe is pegged; however, this assumption is not necessarily valid. In cases where turbidity greatly exceeds the upper measurement limit, turbidity probes can falsely report incorrectly low values of turbidity that appear to be within the limits of the probe. In rivers with limited variation in the physical properties of the suspended sediment, an increase in suspended-sediment concentration will initially cause a linear increase in turbidity. When the suspended-sediment concentration in these rivers causes turbidity levels that exceed the upper measurement limit of a probe, turbidity probes do not necessarily peg at a constant value. Data from the Colorado River in Grand Canyon, Arizona, USA and a laboratory experiment both demonstrate that when turbidity exceeds instrument-pegged conditions, increasing suspended-sediment concentration (and thus increasing turbidity) may cause optical probes to record decreasing false turbidity values that appear to be within the valid measurement range of the probe. Therefore, under high turbidity conditions, other surrogate measurements of turbidity (e.g., acoustic attenuation measurements or suspended-sediment samples) are necessary to correct these low turbidity measurements and accurately measure turbidity.
Hydrofacies reconstruction of glaciofluvial aquifers and groundwater flow modelling in a densely urbanized area under changing climatic conditions
Authors: De Caro Mattia , Crosta Giovanni B. , Frattini Paolo , Perico Roberta , Volpi Giorgio
Published: October 2017

Abstract. Potential impacts of global climate changes on the groundwater are largely unknown, especially for densely populated areas where groundwater is heavily exploited for public and industrial supply. Hence, to better plan and manage the groundwater resources, medium-long term numerical modelling of groundwater flow, which takes into account climate change, population growth, and industrial and agricultural activities, is needed. The objective of this paper is to tackle three main issues: (1) the development of a robust hydro-stratigraphic model of a multi-aquifer system from a well logs database by means of a novel multi-dimensional approach which includes a hierarchical classification of the lithologies, the interpretation of cross-sections, and the interpolation of aquifer boundary surfaces; (2) the parametrization and calibration of both a steady state and a transient groundwater flow model, starting from empirical relationships (for unconfined aquifer) and step-drawdown and well tests (for semi-confined and confined aquifers) to define equivalent homogenous sub-units; and (3) the simulation of steady state and transient scenarios based on projections about global climate change and variation in abstraction and recharge rates. These issues are illustrated for the Milan metropolitan area (Northern Italy) and the conterminous Po Plain portion. The results of the model allow to analyse the major components of the regional groundwater system (i.e. public supply wells withdrawals, discharge to gaining rivers and springs, recharge from irrigation networks and vegetated areas, flow transfer between aquifers). The groundwater level rising observed in the last decades caused serious problems in the urban areas and a progressive increase in the base-flow towards the gaining rivers. Simulations including effects of future climate scenarios (2017–2030) indicate a further increase in groundwater level in the next decades at a lower rate (ca. 0.3 m/year) with respect to that of the 1970–2016 period (ca. 1 m/year), due to the combined action of decreasing withdrawals and recharge.