bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimized Replication Strategy for Intermittently Connected Mobile Networks
Authors: Poongodi C. , Natarajan A. M.
Published: May 2012

Intermittently Connected Mobile Networks (ICMNs) are wireless networks where due to mobility of nodes and lack of connectivity, there may be disconnection among the nodes. Hence, the routing path from source to destination is not always available. In this case, Mobile Ad-hoc Network (MANET) protocols will not be utilized. In these networks, messages are to be flooded or multiple replications are needed to withstand the maximum delay and achieve the high delivery ratio. But multiple replication based protocols result in increased network overhead and high resource consumption because of uncontrolled replication. In this paper, the authors introduce a new simple scheme which applies knapsack policy based replication strategy in replicating the messages. The number of replication is reduced by appropriately selecting only limited messages based on the number of duplications of its own and its size. The messages are selected for forwarding to relay node based on the goodness of the relay node in contacting the destination and the buffer size of the relay node. Therefore, only limited messages will be replicated in the network and it will reduce the network overhead, resource consumption, delivery delay and increases the delivery ratio.
The Impact of a Conditional Cash Transfer Program on Household Income in Colombia
Authors: Hincapié Diana
Published: May 2012

This paper estimates the impact of Familias en Acción, the largest Colombian conditional cash transfer program, on household income. It uses a Quantile Regression methodology and Difference-in-Difference estimators to capture the impact of the program on household income at different quantiles of the income distribution. The estimations show that the program has a positive impact on household income, and that this impact is larger for the households at the lower quantiles of the income distribution. Additional analyses examine whether these results stem from changes in labor market participation or increases in non-labor income. There is some indication that for program participants there was a decrease in labor income, while there was an increase in subsidies or non-labor income. Implications of these findings for conditional cash transfer programs are discussed.
Solving Medicare’s Fiscal Crisis: An Analysis of Three Policy Options
Authors: Flint Ashley
Published: May 2012

Health care spending in the United States has increased rapidly over the past several decades. Medicare, the largest public health insurance program in the US, is a key component of these growing costs. While Medicare financing is expected to be stable over the next decade, the long-term solvency will be difficult to sustain absent congressional action. This paper analyzes three policy options for Congress to consider in addressing the problem of rapid cost growth in the Medicare program.
Developing Safety Cultures in Amtrak and WMATA
Authors: Buckley Mark , Marfione Keith , Putman Hannah
Published: May 2012

Amtrak and the Washington Metropolitan Area Transit Authority (WMATA) have made recent efforts to improve their organizational safety cultures. By transforming their values and behaviors, these transportation organizations sought to reduce employee and passenger accidents and injuries, as well as build more collaborative cultures. This paper illustrates case studies of Amtrak and WMATA and examines the strategies and promising practices that these organizations employed to improve their safety cultures.
The Congressional Budget Office: Honest Numbers, Power, and Policymaking
Authors: Cahill Brian
Published: May 2012

No abstract available.
The Twilight of the Bombs: Recent Challenges, New Dangers, and the Prospects for a World Without Nuclear Weapons
Authors: Rutledge Lauren
Published: May 2012

No abstract available.
Andrew DiRosa, MPA ‘02, Section Chief (Acting) of the Executive Intelligence Section of the Federal Bureau of Investigation
Authors: Brody Rachel , Nadas Joshua
Published: May 2012

Mr. DiRosa obtained a Master’s in Public Administration (MPA), with a focus on managing federal agencies, from The George Washington University in 2002. While at GWU, Andy served as editor of Policy Perspectives, and was awarded the Leadership Award and was inducted into the Pi Alpha Alpha public administration honor society. Andy obtained a BA from Old Dominion University (Norfolk, VA) in English and Political Science in 1987. While at ODU he was elected to two terms on the student senate.Presently, Andy is the assistant section chief of the Executive Intelligence Section in the FBI’s Directorate of Intelligence at FBI Headquarters. In this capacity he helps oversee daily operation of 24-hour units that prepare the daily intelligence briefing materials for the FBI Director, US Attorney General, and other senior executives. Andy has also worked in the FBI’s Counterterrorism Division, as an intelligence analyst and supervisor, and in the FBI’s training division and office of public affairs, as managing editor of the FBI Law Enforcement Bulletin, a widely read criminal justice journal. He authored book reviews and journal articles, including features on street gangs and the impact of the Second World War on US law enforcement. While in the Counterterrorism Division Andy served in an international intelligence cell at NATO headquarters in Brussels. Mr. DiRosa has also represented the FBI at bilateral intelligence exchanges with Canada and the United Kingdom. (Views expressed are those of Mr. DiRosa and do not necessarily reflect the views of the FBI.)
Der 'Pantokrator': Die Inszenierung von Gottes Macht in der Offenbarung des Johannes
Authors: Nicklas Tobias
Published: May 2012

God’s power according to Revelation. The article argues that the ‘power of God’ expressed by the title ‘Pantokrator’ in the Revelation of John should be interpreted against a concrete context and issues about God’s deeds of righteousness. From a human perspective God seems to be passive and silent concerning the suffering of believers caused by the enemies of God. However, God’s sovereignty transcends all secular and supernatural powers. The power of God manifests itself in the acts of Jesus the Messiah whose power is paradoxically proclaimed by his being described as both a lion and a lamb.
Building the local church in South Korea through a needs-oriented diaconal ministry
Authors: Yun Janghun
Published: May 2012

According to Acts 20:28, God acquired the Church for himself with the blood of his own Son, whilst Ephesians 4:13, 15 proposes that the Church, the body of Christ, has to grow towards the measure of the fullness of Christ and into Christ. For this to succeed, there must be a comprehensive approach to building the local church, even though it may not have a single element that could account for congregational development. Building the local church (BLC) through a needs-oriented diaconal ministry (NDM) that meets effectively the needs of the community and its people by providing the essential functions of the church, such as koinonia, diakonia, kerygma and leitourgia in synergy, will be helpful to congregational development, functioning as a living organism that leads church members to vitality and equips them to fulfil the variety of works available in the body of Christ. This article focused on two key factors that can be used to develop a sound and effective BLC through NDM, namely, (1) BLC through NDM supports a sound theory of congregational development and (2) BLC through NDM makes for an effective strategy to promote congregational studies. To this end, this article presented and interpreted data from a case study of the baby schools of Choongshin Church and Daegwang Church and the pregnant women’s group of Daegwang Church in South Korea, in order to prove the soundness and effectiveness of BLC through NDM and suggest a diagram of BLC through NDM. When BLC through NDM is utilised fully and applied to the missionary strategy in urban areas, more people will become meaningfully involved in Christian life and membership of the churches.
Different Evolutionary Modifications as a Guide to Rewire Two-Component Systems
Authors: Krueger Beate , Friedrich Torben , Förster Frank , Bernhardt Jörg , Gross Roy , Dandekar Thomas
Published: May 2012

Two-component systems (TCS) are short signalling pathways generally occurring in prokaryotes. They frequently regulate prokaryotic stimulus responses and thus are also of interest for engineering in biotechnology and synthetic biology. The aim of this study is to better understand and describe rewiring of TCS while investigating different evolutionary scenarios.

Based on large-scale screens of TCS in different organisms, this study gives detailed data, concrete alignments, and structure analysis on three general modification scenarios, where TCS were rewired for new responses and functions: (i) exchanges in the sequence within single TCS domains, (ii) exchange of whole TCS domains; (iii) addition of new components modulating TCS function.

As a result, the replacement of stimulus and promotor cassettes to rewire TCS is well defined exploiting the alignments given here. The diverged TCS examples are non-trivial and the design is challenging. Designed connector proteins may also be useful to modify TCS in selected cases.
Milnacipran Hydrochloride in the Treatment of Fibromyalgia Syndrome: Safety, Efficacy and Tolerability
Authors: Smith Howard S. , Meek Patrick D.
Published: May 2012

Fibromyalgia is a central sensitization disorder characterized by chronic widespread pain, nonrestorative sleep, fatigue, cognitive dysfunction as well as a number of somatic symptoms; that reduces physical/emotional function/quality of life. Treatment options include: Patients education, behavioral medicine strategies, (eg, cognitive behavioral therapy), physical medicine strategies (eg, exercise/aerobic and strength training), and pharmacologic agents.

Currently there are three agents approved by the US Federal Drug Administration for the treatment of Fibromyalgia: pregabalin, duloxetine, and milnacipran. Milnacipran is a norepinephrine-serotonin reuptake inhibitor that is only approved in the US for fibromyalgia. It has 3-fold increased selectivity for norepinephrine compared to serotonin. Milnacipran is well absorbed (85% bioavailability), has a half-life of 6-8 hours, and does not undergo cytochrome P450 metabolism. Milnacipran in doses of 50 mg PO BID to 100 mg PO BID has been shown to have efficacy for fibromyalgia. The most common adverse effect is nausea.
Evaluation of Salivary Antioxidant Enzymes among Smokers and Nonsmokers
Authors: Masthan KMK , Saggu Tajinder Kaur , Dudanakar Mahesh Pundaleek , Nisa Shams UI
Published: May 2012

Background

Cigarette smoke contains various oxygen-free radicals which are considered as the main causes of damage to biomolecules when exposed to cigarette smoke. Saliva is the first biological fluid that encounters inhaled cigarette smoke (CS) and has an antioxidant defense system able to counter toxic activities of free radical species. So, the aim of this study was to compare the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in saliva of smokers and nonsmokers.

Materials and methods

Unstimulated saliva of 200 males (100 smokers and 100 nonsmokers) was collected. The saliva was centrifuged and the activity of salivary superoxide dismutase and glutathione peroxidase was measured according to a specific assay.

Results

The mean value of superoxide dismutase activity was significantly higher in the smoking group than in the nonsmoker group, while the levels of GSH-Px activity was significantly higher in the nonsmoking group than in the smoking group.

Conclusion

Cigarette smoke leads to an alteration in salivary antioxidant activity. Evaluating the variations in the level of antioxidant enzymes (SOD and GSH-Px) in smoker's saliva might be useful for estimating the level of oxidative stress caused by cigarette smoke. Thus, it may help in patient's education regarding the ill-effects of smoking and determining the evolution and progress of various oral diseases.

How to cite this article

Saggu TK, Masthan KMK, Dudanakar MP, Nisa SUI, Patil S. Evaluation of Salivary Antioxidant Enzymes among Smokers and Nonsmokers. World J Dent 2012;3(1):18-21.
Evaluation of Electric Discharge Machining to achieve Passive Fit of Implant Superstructure: An in vitro Study
Authors: Shah Siddharth
Published: May 2012

Objective

To evaluate marginal discrepancies between cast implant superstructure and EDM processed implant structure.

Materials and methods

For the purpose of this study, an experimental model was prepared on which nine cast implant superstructure in nickel-chromium were fabricated which was then subjected to EDM processing. One-screw test was used to verify fit of superstructure both pre- and post-EDM processing. Photo/Image analyzer was used to evaluate the marginal discrepancy. To reduce the error of measurement, nine readings were taken of each implant abutment junction, i.e. overall 324 readings pre- and post-EDM processing was made.

Results

All implant superstructure fabricated by investment casting procedure in nickel-chromium alloy showed negative one-screw test, i.e. they were fitting actively on abutment head and were sitting passively after EDM processing. Mean marginal opening of cast implant superstructure before EDM processing was 95.93 microns and 22.76 microns after EDM processing.

Conclusion

Nickel-chromium alloy can be used for fabrication of implant superstructure with EDM as programmed refining procedure to achieve passive fit.

How to cite this article

Shah S. Evaluation of Electric Discharge Machining to achieve Passive Fit of Implant Superstructure: An in vitro Study. World J Dent 2012;3(1): 32-36.
Dentin Hypersensitivity—Etiology, Treatment Possibilities and Other Related Factors: A Literature Review
Authors: Barcellos Daphne Câmara , Borges Alessandra Buhler , Torres Carlos Rocha Gomes , Borges Alexandre Luiz Souto , Marsilio Ana Lucia , Carvalho Cláudio Antonio Talge
Published: May 2012

Dentinal hypersensitivity is a common painful condition of the teeth, associated with the exposure of the dentin to external environment of the mouth. However, little is known about the etiology and predisposing factors, which can compromise management. The aim of this paper is to summarize existing information about epidemiology, mechanisms, etiology, differential diagnosis and treatment.

Clinical relevance

A better understanding of the etiology and factors involved in dentin hypersensitivity will help the management of the hypersensitivity teeth.

How to cite this article

Borges AB, Barcellos DC, Torres CRG, Borges ALS, Marsilio AL, Carvalho CAT. Dentin Hypersensitivity— Etiology, Treatment Possibilities and Other Related Factors: A Literature Review. World J Dent 2012;3(1):60-67.
Issues in Professional Judgment: Antibiotic Prophylaxis in Client with Prosthetic Joint
Authors: Pickett Frieda A
Published: May 2012

Issues related to clinical decision-making regarding prescribing antibiotic prophylaxis prior to oral procedures for the client with a prosthetic joint are discussed.

Method

PubMed and relevant professional guidelines were searched for research and for evidence-based guidelines.

Outcome

There is a need for evidence-based guidelines developed by stakeholders including the American Academy of Orthopedic Surgeons, the American Dental Association and the Infectious Disease Society. There is an absence of level 1 evidence for or against the use of prophylactic antibiotics in patients with prosthetic joints undergoing invasive dental treatment. Therefore, until the professional organizations provide evidence-based guidance, professional judgment must depend on the client history following joint replacement and the state of the host immune response.

How to cite this article

Pickett FA. Issues in Professional Judgment: Antibiotic Prophylaxis in Client with Prosthetic Joint. World J Dent 2012;3(1):74-76.
Complete Denture Fabrication for Old Denture Wearer in One Day
Authors: Murthy S Srinivasa , Prabhu M Bharath , Hegde Mayur , Murthy Gargi S
Published: May 2012

Complete dentures fabrication conventionally requires 4 to 5 visits to the clinic. It will be sometimes very demanding for aged patients and also for the dentist. Here, in this article, technique of complete denture construction in one day for an old denture wearer is described. Wherein the old denture is used as special tray and also as record base. Secondary impression with border moulding and jaw relation is completed in one visit with old dentures. Teeth arrangement try-in is not given and finished in one day.

How to cite this article

Murthy SS, Prabhu MB, Hegde M, Murthy GS. Complete Denture Fabrication for Old Denture Wearer in One Day. World J Dent 2012;3(1):112-114.
Functional Impression for Hemimandibulectomy Cases: An Alternative Technique
Authors: Rao Srinivas , Akki Savita F
Published: May 2012

The altered cast impression technique is preferred to derive maximum support from the residual ridge in the distal extension partial denture hemimandibulectomy cases. The traditional method is designed primarily for making a secondary impression of the ridge in the functional form to correct a master cast. These functional impression techniques are time-consuming and involve multiple steps.

This article describes a new clinical and laboratory technique in impression making. Emphasis is placed on recording the anatomical form of teeth and functional form of the residual ridge in an individual tray using two different impression materials eliminating secondary impression.
Reattachment of Fractured Anterior Tooth: A 2-Year Review of a Case
Authors: Mojirade Ajayi Deborah , Funmilayo Abiodun-Solanke IM , Olaide Gbadebo Shakeerah
Published: May 2012

Injury to anterior teeth is a relatively common occurrence. Dentists are confronted on regular basis with dental trauma and the management. Some clinical studies have reported reattachment of fractured tooth segment using adhesive resin cement and dentine bonding agent with or without intraradicular postplacement. Reattachment of tooth fragment is simple and can provide good functional and esthetic success.

Case description

This article reports the reattachment of a fractured anterior tooth in a 17-year-old male patient with adhesive resin and a prefabricated metallic post.

Result

Evaluation at 2 years revealed good reattachment, intact post, good esthetics (even after a repeat reattachment) and good periodontal health.
“Não estou mais sozinha!”: mudanças no processo de decisão de compra de consumidoras primigrávidas
Authors: De Faria Marina Dias , Chauvel Marie Agnes , Gaia Patricia , Hallak Rodrigo
Published: May 2012

A escassez de estudos em administração que tenham como foco o comportamento da mulher como consumidora durante o período de gestação motivou a elaboração da pesquisa. Estabeleceu-se como objetivo de pesquisa identificar as principais mudanças no processo de tomada de decisão de compra de mulheres durante a primeira gravidez, com foco nas mudanças relativas à compra de itens de uso pessoal das grávidas. Para atingir o objetivo foram realizadas entrevistas semiestruturadas em profundidade com 72 gestantes de primeira viagem (primigrávidas), com pelo menos quatro meses de gravidez, em locais na Zona Sul do Rio de Janeiro. Os resultados mostram que são muitas as mudanças que ocorrem no processo de tomada de decisão durante a gestação. Quanto ao que comprar, de modo geral, a prioridade passa a ser aquilo de que o bebê precisa. A preocupação em buscar uma alimentação saudável cresce; a prática de atividades físicas é intensificada, bem como o consumo de cremes estéticos. Em contrapartida, o consumo de roupas é menor. O tempo despendido na busca por informações e avaliação de alternativas são maiores do que antes da gravidez. Uma das entrevistadas estava grávida de um bebê com deficiência e alguns pontos levantados por ela foram peculiares.
O modelo de Karl Popper sob a ótica das Ciências Sociais Aplicadas
Authors: Campanario Milton de Abreu , Chagas Junior Milton de Freitas , Ruiz Mauro Silva
Published: May 2012

Karl Popper é o principal filósofo da ciência na modernidade, disputando com Thomas Kuhn a primazia de interpretação do método científico. Claramente há diferentes visões para uma leitura desse importante autor que cunhou o método chamado de dedutivo com teste. O texto reconhece a relevância da visão de Karl Popperno desenvolvimento de trabalhos científicos das ciências exatas e biológicas, onde é amplamente aceita. No entanto, nota-se que essa formulação é pouco sistematizada na área das ciências sociais aplicadas. Este é um ensaio que busca resgatar a sua contribuição, numa tentativa de traduzir os conceitos por ele desenvolvidos de forma didática. Para tanto, será feita uma introdução aos fundamentos da ciência como forma específica de conhecimento, buscando contrastar os métodos dedutivo e indutivo e os procedimentos da ciência formal, básica e aplicada. Uma tentativa de classificar a formulação de proposições a serem testadas ou falseadas é feita com a utilização de diferentes critérios, utilizando exemplos da administração e da economia para ilustração.
O processo de liderança e a gestão do conhecimento organizacional: as práticas das maiores indústrias catarinenses
Authors: Girardi Dante Marciano , Souza Irineu Manoel de , Freitas Girardi Júlia
Published: May 2012

O objetivo deste artigo é apresentar as práticas de liderança das indústrias catarinenses de grande porte e a sua contribuição para a Gestão do Conhecimento. A competitividade organizacional está relacionada às pessoas e à capacidade das empresas de fomentar o desenvolvimento constante do conhecimento. Por meio da liderança, os gestores e a Gestão de Pessoas criam comprometimento e melhoram os resultados das organizações. A metodologia adotada seguiu a linha da pesquisa qualitativa, descritiva e aplicada. Foram entrevistadas as sete maiores indústrias do Estado de Santa Catarina, em número de colaboradores. Utilizou-se também a pesquisa documental. Os dados foram analisados pela técnica de análise de conteúdo. Observou-se que a liderança está presente na maioria das empresas estudadas, por meio de programas formais de desenvolvimento de líderes ou de ações relacionadas à liderança. Conclui-se que as empresas têm o foco nas pessoas e no conhecimento, em maior ou menor grau, estando algumas em fase de transição e de revisão dos programas voltados ao desenvolvimento dos seus talentos e à Gestão do Conhecimento.
The IPAC-NC field campaign: a pollution and oxidization pool in the lower atmosphere over Huabei, China
Authors: Ma J. Z. , Wang W. , Chen Y. , Liu H. J. , Yan P. , Ding G. A. , Wang M. L. , Sun J. , Lelieveld J.
Published: May 2012

Abstract. In the past decades, regional air pollution characterized by photochemical smog and grey haze-fog has become a severe environmental problem in China. To investigate this, a field measurement campaign was performed in the Huabei region, located between 32–42° N latitude in eastern China, during the period 2 April–16 May 2006 as part of the project "Influence of Pollution on Aerosols and Cloud Microphysics in North China" (IPAC-NC). It appeared that strong pollution emissions from urban and industrial centers tend to accumulate in the lower atmosphere over the central area of Huabei. We observed widespread, very high SO2 mixing ratios, about 20–40 ppbv at 0.5–1.5 km altitude and 10–30 ppbv at 1.5–3.0 km altitude. Average CO mixing ratios were 0.65–0.7 ppmv at 0.5–1.5 km altitude, and very high CO around 1 ppmv was observed during some flights, and even higher levels at the surface. We find the high pollution concentrations to be associated with enhanced levels of OH and HO2 radicals, calculated with a chemical box model constrained by the measurements. In the upper part of the boundary layer and in the lower free troposphere, high CO and SO2 compete with relatively less NO2 in reacting with OH, being efficiently recycled through HO2, preventing a net loss of HOx radicals. In addition to reactive hydrocarbons and CO, the oxidation of SO2 causes significant ozone production over Huabei (up to ~13% or 2.0 ppbv h−1 at 0.8 km altitude). Our results indicate that the lower atmosphere over Huabei is not only strongly polluted but also acts as an oxidation pool, with pollutants undergoing very active photochemistry over this part of China.
Chamber studies of SOA formation from aromatic hydrocarbons: observation of limited glyoxal uptake
Authors: Nakao S. , Liu Y. , Tang P. , Chen C.-L. , Zhang J. , Cocker III D. R.
Published: May 2012

Abstract. This study evaluates the significance of glyoxal acting as an intermediate species leading to secondary organic aerosol (SOA) formation from aromatic hydrocarbon photooxidation under humid conditions. Rapid SOA formation from glyoxal uptake onto aqueous (NH4)2SO4 seed particles is observed in agreement with previous studies; however, glyoxal did not partition significantly to SOA (with or without aqueous seed) during aromatic hydrocarbon photooxidation within an environmental chamber (RH less than 80%). Rather, glyoxal influences SOA formation by raising hydroxyl (OH) radical concentrations. Four experimental approaches supporting this conclusion are presented in this paper: (1) increased SOA formation and decreased SOA volatility in the toluene + NOx photooxidation system with additional glyoxal was reproduced by matching OH radical concentrations through H2O2 addition; (2) glyoxal addition to SOA seed formed from toluene + NOx photooxidation did not increase SOA volume under dark; (3) SOA formation from toluene + NOx photooxidation with and without deliquesced (NH4)2SO4 seed resulted in similar SOA growth, consistent with a minor contribution from glyoxal uptake onto deliquesced seed and organic coatings; and (4) the fraction of a C4H9+ fragment (observed by Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer, HR-ToF-AMS) in SOA from 2-tert-butylphenol (BP) oxidation was unchanged in the presence of additional glyoxal despite enhanced SOA formation. This study suggests that glyoxal uptake onto aerosol during the oxidation of aromatic hydrocarbons is more limited than previously thought.
Estimating the climate significance of halogen-driven ozone loss in the tropical marine troposphere
Authors: Saiz-Lopez A. , Lamarque J.-F. , Kinnison D. E. , Tilmes S. , Ordóñez C. , Orlando J. J. , Conley A. J. , Plane J. M. C. , Mahajan A. S. , Sousa Santos G. , Atlas E. L. , Blake D. R. , Sander S. P. , Schauffler S. , Thompson A. M. , Brasseur G.
Published: May 2012

Abstract. We have integrated observations of tropospheric ozone, very short-lived (VSL) halocarbons and reactive iodine and bromine species from a wide variety of tropical data sources with the global CAM-Chem chemistry-climate model and offline radiative transfer calculations to compute the contribution of halogen chemistry to ozone loss and associated radiative impact in the tropical marine troposphere. The inclusion of tropospheric halogen chemistry in CAM-Chem leads to an annually averaged depletion of around 10% (~2.5 Dobson units) of the tropical tropospheric ozone column, with largest effects in the middle to upper troposphere. This depletion contributes approximately −0.10 W m−2 to the radiative flux at the tropical tropopause. This negative flux is of similar magnitude to the ~0.33 W m−2 contribution of tropospheric ozone to present-day radiative balance as recently estimated from satellite observations. We find that the implementation of oceanic halogen sources and chemistry in climate models is an important component of the natural background ozone budget and we suggest that it needs to be considered when estimating both preindustrial ozone baseline levels and long term changes in tropospheric ozone.
On dithiothreitol (DTT) as a measure of oxidative potential for ambient particles: evidence for the importance of soluble transition metals
Authors: Charrier J. G. , Anastasio C.
Published: May 2012

Abstract. The rate of consumption of dithiothreitol (DTT) is increasingly used to measure the oxidative potential of particulate matter (PM), which has been linked to the adverse health effects of PM. While several quinones are known to be very reactive in the DTT assay, it is unclear what other chemical species might contribute to the loss of DTT in PM extracts. To address this question, we quantify the rate of DTT loss from individual redox-active species that are common in ambient particulate matter. While most past research has indicated that the DTT assay is not sensitive to metals, our results show that seven out of the ten transition metals tested do oxidize DTT, as do three out of the five quinones tested. While metals are less efficient at oxidizing DTT compared to the most reactive quinones, concentrations of soluble transition metals in fine particulate matter are generally much higher than those of quinones. The net result is that metals appear to dominate the DTT response for typical ambient PM2.5 samples. Based on particulate concentrations of quinones and soluble metals from the literature, and our measured DTT responses for these species, we estimate that for typical fine particle samples approximately 80% of DTT loss is from transition metals (especially copper and manganese), while quinones account for approximately 20%. We find a similar result for DTT loss measured in a small set of PM2.5 samples from the San Joaquin Valley of California. Because of the important contribution from metals, we also tested how the DTT assay is affected by EDTA, a chelator that is sometimes used in the assay. EDTA significantly suppresses the response from both metals and quinones; we therefore recommend that EDTA should not be included in the DTT assay.
Vertical transport of pollutants by shallow cumuli from large eddy simulations
Authors: Chen G. , Xue H. , Feingold G. , Zhou X.
Published: May 2012

Abstract. This study investigates the vertical transport of a passive tracer in a shallow cumulus boundary layer using large eddy simulations. The tracer source is at the surface in one case, and in the inversion layer in the other case. Results show that shallow cumulus clouds can significantly enhance vertical transport of the tracer in both cases. In the case with surface-borne pollutants, cloudy regions are responsible for the upward transport, due to the intense updrafts in cumulus clouds. In the case where pollutants are aloft, cloud-free regions are responsible for the downward transport, but the downward transport mainly occurs in thin regions around cloud edges. This is consistent with previous aircraft measurements of downdrafts around cumulus clouds and indicates that the downward transport is also cloud-induced. We also preformed cloud-free sensitivity runs for the two cases. Results show that this dry convection can neither transport the surface-borne pollutants into the inversion layer, nor transport pollutants from the inversion layer downward to the lower boundary layer. Cumulus convection is therefore more effective than dry convection at venting pollutants upward from the surface, and fumigating pollutants in the inversion layer downward into the lower boundary layer.
Particle hygroscopicity during atmospheric new particle formation events: implications for the chemical species contributing to particle growth
Authors: Wu Z. , Birmili W. , Poulain L. , Merkel M. , Fahlbusch B. , van Pinxteren D. , Herrmann H. , Wiedensohler A.
Published: May 2012

Abstract. This study examines the hygroscopicity of newly formed particles (smaller than 50 nm in particle mobility diameter) during two atmospheric new particle formation events with and without clear growth process at mid-level mountain range in Central Germany based on HCCT field campaign. Particle hygroscopicity measurements show that the particle soluble fractions at the end of event for two events are, respectively 60% (45 nm particles for the event with clear growth) and 20% (30 nm particles for the event without clear growth), stressing that non-soluble organic compounds may play a key role in particle growth during new particle formation event. Such significant difference in particle hygroscopicity also suggests that the chemical species responsible for nucleation particle growth are considerably different between the two selected NPF events. During both events, the hygroscopicity of newly formed particles decreased with particle growth, indicating that more less-hygroscopic compounds contribute to the subsequent condensation in contrast to the earlier stage. Sulfuric acid was considered to be responsible of the NPF event and represent the highly hygroscopic compounds. However, calculation demonstrated that sulfuric acid condensation failed to fully explain the observed soluble fraction in the nucleation mode particles. Therefore, we hypothesize that some water-soluble matters may explain the missing soluble fraction.
NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy
Authors: Chan K. L. , Pöhler D. , Kuhlmann G. , Hartl A. , Platt U. , Wenig M. O.
Published: May 2012

Abstract. In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30–14:30 LT – local time).
Tropospheric BrO column densities in the Arctic from satellite: retrieval and comparison to ground-based measurements
Authors: Sihler H. , Platt U. , Beirle S. , Marbach T. , Kühl S. , Dörner S. , Verschaeve J. , Frieß U. , Pöhler D. , Vogel L. , Sander R. , Wagner T.
Published: May 2012

Abstract. During polar spring, halogen radicals like bromine monoxide (BrO) play an important role in the chemistry of tropospheric ozone destruction. Satellite measurements of the BrO-distribution have become a particularly useful tool to investigate this probably natural phenomenon, but the separation of stratospheric and tropospheric partial columns of BrO is challenging. In this study, an algorithm was developed to retrieve tropospheric vertical column densities of BrO from data of high-resolution spectroscopic satellite instruments such as the second Global Ozone Monitoring Experiment (GOME-2). Unlike recently published approaches, the presented algorithm is capable of separating the fraction of BrO in the activated troposphere from the total BrO column solely based on remotely measured properties. The sensitivity of each satellite pixel to BrO in the boundary-layer is quantified using the measured UV-radiance and the column density of the oxygen collision complex O4. A comparison of the sensitivities with CALIPSO LIDAR observations demonstrates that clouds shielding near-surface trace-gas columns can be reliably detected even over ice and snow. Retrieved tropospheric BrO columns are then compared to ground-based BrO measurements from two Arctic field campaigns in the Amundsen Gulf and at Barrow in 2008 and 2009, respectively. Our algorithm was found to be capable of retrieving enhanced near-surface BrO during both campaigns in good agreement to ground-based data. Some differences between ground-based and satellite measurements observed at Barrow can be explained by both, elevated and shallow surface layers of BrO. The observations strongly suggest that surface release processes are the dominating source of BrO and that boundary-layer meteorology influences the vertical distribution.
The influence of model grid resolution on estimation of national scale nitrogen deposition and exceedance of critical loads
Authors: Dore A. J. , Kryza M. , Hall J. R. , Hallsworth S. , Keller V. J. D. , Vieno M. , Sutton M. A.
Published: May 2012

Abstract. The Fine Resolution Atmospheric Multi-pollutant Exchange model (FRAME) was applied to model the spatial distribution of reactive nitrogen deposition and air concentration over the United Kingdom at a 1 km spatial resolution. The modelled deposition and concentration data were gridded at resolutions of 1 km, 5 km and 50 km to test the sensitivity of calculations of the exceedance of critical loads for nitrogen deposition to the deposition data resolution. The modelled concentrations of NO2 were validated by comparison with measurements from the rural sites in the national monitoring network and were found to achieve better agreement with the high resolution 1 km data. High resolution plots were found to represent a more physically realistic distribution of reactive nitrogen air concentrations and deposition resulting from use of 1 km resolution precipitation and emissions data as compared to 5 km resolution data. Summary statistics for national scale exceedance of the critical load for nitrogen deposition were not highly sensitive to the grid resolution of the deposition data but did show greater area exceedance with coarser grid resolution due to spatial averaging of high nitrogen deposition hot spots. Local scale deposition at individual Sites of Special Scientific Interest and high precipitation upland sites was sensitive to choice of grid resolution of deposition data. Use of high resolution data tended to generate lower deposition values in sink areas for nitrogen dry deposition (Sites of Scientific Interest) and higher values in high precipitation upland areas. In areas with generally low exceedance (Scotland) and for certain vegetation types (montane), the exceedance statistics were more sensitive to model data resolution.
Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?
Authors: Sintermann J. , Neftel A. , Ammann C. , Häni C. , Hensen A. , Loubet B. , Flechard C. R.
Published: May 2012

Abstract. The EMEP/EEA guidebook 2009 for agricultural emission inventories reports an average ammonia (NH3) emission factor (EF) by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN) content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique or measurement plot size and year of measurement. Medium size plots (usually circles between 20 to 50 m radius) generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method)). Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002). More recent measurements show substantially lower EFs which calls for new measurement series in order to validate the various measurement approaches against each other and to derive revised inputs for inclusion into emission inventories.
Regional analysis of groundwater nitrate concentrations and trends in Denmark in regard to agricultural influence
Authors: Hansen B. , Dalgaard T. , Thorling L. , Sørensen B. , Erlandsen M.
Published: May 2012

Abstract. The act of balancing between an intensive agriculture with a high potential for nitrate pollution and a~drinking water supply almost entirely based on groundwater is a challenge faced by Denmark and similar regions around the globe. Since the 1980s, regulations implemented by Danish farmers have succeeded in optimizing the N (nitrogen) management at farm level. As a result, the upward agricultural N surplus trend has been reversed, and the N surplus has reduced by 30–55 % from 1980 to 2007 depending on region. The reduction in the N surplus served to reduce the losses of N from agriculture, with documented positive effects on nature and the environment in Denmark. In groundwater, the upward trend in nitrate concentration was reversed around 1980, and a larger number of downward nitrate trends were seen in the youngest groundwater compared with the oldest groundwater. However, on average, approximately 48 % of the oxic monitored groundwater has nitrate concentrations above the groundwater and drinking water standards of 50 mg l−1. Furthermore, trend analyses show that 33 % of all the monitored groundwater has upward nitrate trends, while only 18 % of the youngest groundwater has upward nitrate trends according to data sampled from 1988–2009. A regional analysis shows a correlation between a high level of N surplus in agriculture, high concentrations of nitrate in groundwater and the largest number of downward nitrate trends in groundwater in the livestock-dense northern and western parts of Denmark compared with the south-eastern regions with lower livestock densities. These results indicate that the livestock farms dominating in northern and western parts of Denmark have achieved the largest reductions in N surpluses. Groundwater recharge age determinations allow comparison of long-term changes in N surplus in agriculture with changes in oxic groundwater quality. The presented data analysis is based on groundwater recharged from 1952–2003, but sampled from 1988–2009. Repetition of the nitrate trend analyses at five-year intervals using dating of the groundwater recharged in the coming years and a longer time series of the nitrate analyses can reveal the evolution in nitrate leaching from Danish agriculture during the past 10 yr. Similar analyses can be carried out to compare with other regions internationally.
Precipitation variability in the winter rainfall zone of South Africa during the last 1400 yr linked to the austral westerlies
Authors: Stager J. C. , Mayewski P. A. , White J. , Chase B. M. , Neumann F. H. , Meadows M. E. , King C. D. , Dixon D. A.
Published: May 2012

Abstract. The austral westerlies strongly influence precipitation and ocean circulation in the southern temperate zone, with important consequences for cultures and ecosystems. Global climate models anticipate poleward retreat of the austral westerlies with future warming, but the available paleoclimate records that might test these models have been limited to South America and New Zealand, are not fully consistent with each other and may be complicated by influences from other climatic factors. Here we present the first high-resolution diatom and sedimentological records from the winter rainfall region of South Africa, representing precipitation in the equatorward margin of the westerly wind belt during the last 1400 yr. Inferred rainfall was relatively high ∼1400–1200 cal yr BP, decreased until ∼950 cal yr BP, and rose notably through the Little Ice Age with pulses centred on ∼600, 530, 470, 330, 200, 90, and 20 cal yr BP. Synchronous fluctuations in Antarctic ice core chemistry strongly suggest that these variations were linked to changes in the westerlies. Equatorward drift of the westerlies during the wet periods may have influenced Atlantic meridional overturning circulation by restricting marine flow around the tip of Africa. Apparent inconsistencies among some aspects of records from South America, New Zealand and South Africa warn against the simplistic application of single records to the Southern Hemisphere as a whole. Nonetheless, these findings in general do support model projections of increasing aridity in the austral winter rainfall zones with future warming.
Stable isotope and trace element investigation of two contemporaneous annually-laminated stalagmites from northeastern China surrounding the "8.2 ka event"
Authors: Wu J. Y. , Wang Y. J. , Cheng H. , Kong X. G. , Liu D. B.
Published: May 2012

Abstract. The prominent "8.2 ka event" was well documented in the Greenland ice cores. It remains unclear, however, about its duration, structure and forcing mechanism at low- to mid-latitude regions. Here we use the physical and geochemical data of stalagmites from the Nuanhe Cave in Liaoning province, northeastern China to reconstruct a detailed history of East Asian monsoons throughout the event. Two contemporaneous stalagmites were annually counted for at least 770 yr anchored by five 230Th dates to establish an inter-calibrated high-resolution timescale. Two oxygen isotope profiles replicate each other at annual-decadal timescales although their counted growth rates are not consistent, indicating that the δ18O variability has a climatic origin, largely associated with changes in the rainfall δ18O from the West Pacific during summer season. A signal from the "8.2 ka event" was faint in our δ18O records, not as significant as Indian monsoon dominated stalagmite δ18O records from Qunf in Oman and Dongge in Southern China. However, our δ13C and Ba/Ca profiles, as indicators of local environmental changes, provide a strong support for a deteriorated climate episode centred at 8.2 ka BP, likely controlled by winter monsoon circulations via the westerly winds associated with North Atlantic climates. Therefore, we concluded that the winter- and summer-Asian monsoons responded independently to the high northern latitude climates.
Two weather radar time series of the altitude of the volcanic plume during the May 2011 eruption of Grímsvötn, Iceland
Authors: Petersen G. N. , Bjornsson H. , Arason P. , von Löwis S.
Published: May 2012

Abstract. The eruption of Grímsvötn volcano in Iceland in 2011 lasted for a week, 21–28 May. The eruption was explosive and peaked during the first hours, with the eruption plume reaching 20–25 km altitude. The height of the plume was monitored every 5 min with a C-band weather radar located at Keflavík International Airport and a mobile X-band radar, 257 km and 75 km distance from the volcano, respectively. In addition, photographs taken during the first half-hour of the eruption give information regarding the initial rise. Time series of the plume-top altitude were constructed from the radar observations. This paper presents the two independent radar time series. The series have been cross validated and there is a good agreement between the time series. The echo top radar series of the altitude of the volcanic plume are publicly available from the Pangaea Data Publisher (http://doi.pangaea.de/10.1594/PANGAEA.778390).