bluuebunny/crossref_metadata_2025 huggingface dataset:
Total Economic Cost and Burden of Dengue in Nicaragua: 1996–2010
Authors: Wettstein Zachary S. , Fleming Michael , Chang Aileen Y. , Copenhaver David J. , Wateska Angela R. , Bartsch Sarah M. , Lee Bruce Y. , Kulkarni Rajan P.
Published: September 2012

The burden of dengue in Nicaragua has been steadily rising during the last three decades; however, there have been few efforts to quantify the burden (measured in disability-adjusted life years [DALYs]) and cost to society. Using primary data from the Nicaraguan Ministry of Health (MINSA), the total cost and burden of dengue were calculated from 1996 to 2010. Total costs included both direct costs from medical expenditures and prevention activities and indirect costs from lost productivity. The annual disease burden ranged from 99 to 805 DALYs per million, with a majority associated with classic dengue fever. The total cost was estimated to be US$13.5 million/year (range: US$5.1–27.6 million). This analysis can help improve allocation of dengue control resources in Nicaragua and the region. As one of the most comprehensive analyses of its type to date in Nicaragua and Latin America, this study can serve as a model to determine the burden and cost of dengue.
Fatal Co-Infection–Melioidosis and Leptospirosis
Authors: Hin How Soon , Ramalingam Rajalingam , Chunn Kuan Yeh , Ahmad Norazah , Ab Rahman Jamalludin , Mohamed Mohd Sapian
Published: September 2012

Co-infection of melioidosis and leptospirosis is uncommon. We report here four such cases, confirmed by blood culture for melioidosis and blood polymerase-chain reaction for leptospirosis, which occurred among rescuers involved in a search and rescue operation for a young man who was suspected to have drowned in Lubuk Yu, a recreational forest in Pahang, Malaysia. Despite treatment, three of the patients died from the co-infection.
ELISA with Recombinant rKRP42 Antigen Using Urine Samples: A Tool for Predicting Clinical Visceral Leishmaniasis Cases and Its Outbreak
Authors: Islam Mohammad Zahidul , Itoh Makoto , Islam Md. Anwar Ul , Saifuddin Ekram A. R. M. , Rahman Md. Ajijur , Takagi Hidekazu , Takesue Atsuhide , Hashiguchi Yoshihisa , Kimura Eisaku
Published: September 2012

We reported a highly sensitive and specific enzyme-linked immunosorbent assay (ELISA) that detects immunoglobulin G (IgG) in urine using rKRP42 antigen for the diagnosis of visceral leishmaniasis (VL). The ELISA was applied to study chronological change in antibody titers in five study areas in Rajshahi district, Bangladesh. A total of 585 subjects without a past VL history were examined at least three times in the 30-month follow-up period; of these subjects, 137 (23.4%) subjects became ELISA-positive at least one time during the study. Among the positive cases, 40 (29.2%) subjects developed clinical VL, and 31 (77.5%) of these subjects showed IgG titers of ≥ 1,000 U more than one time in the study period. Considering only the first ELISA results, 22 subjects with IgG titers of ≥ 1,000 U could be found, and 21 (95.5%) of these subjects turned out to be clinical cases. The high urinary IgG titers (≥ 1,000 U) will help predict possible clinical VL cases and thus, identify an outbreak in its earlier stage.
The Development of a Loop-Mediated Isothermal Amplification Method (LAMP) for Echinococcus granulosis Coprodetection
Authors: Salant Harold , Abbasi Ibrahim , Hamburger Joseph
Published: September 2012

We have previously developed a polymerase chain reaction (PCR) assay for detection of Echinococcus granulosus infection, which proved very sensitive and specific for identification of infected dogs. We have now developed a loop-mediated isothermal amplification (LAMP) assay, which amplifies the same genomic repeated sequences of E. granulosus for coprodetection. This assay enabled detection of a single egg in fecal samples and showed high species specificity for E. granulosus with no cross-amplification of DNA from closely related helminths, including Echinococcus multilocularis. Because the method does not require thermocycling for DNA amplification, or electrophoresis for amplicon detection, it can potentially be used for premortem identification of E. granulosus-infected dogs to enable large-scale surveys in endemic countries where highly specialized equipment to undertake PCR analysis is rare.
Pooled Testing for Effective Estimation of the Prevalence of Schistosoma mansoni
Authors: Mitchell Shira , Pagano Marcello
Published: September 2012

Rapid and accurate identification of the prevalence of schistosomiasis is key for control and eradication of this devastating disease. The current screening standard for intestinal schistosomiasis is the Katz-Kato method, which look for eggs on slides of fecal matter. Although work has been done to estimate prevalence using the number of eggs on a slide, the procedure is much faster if the laboratory only reports the presence or absence of eggs on each slide. To further help reduce screening costs while maintaining accuracy, we propose a pooled method for estimating prevalence. We compare it to the standard individualed method, investigating differences in efficiency, measured by the number of slides read, and accuracy, measured by mean square error of estimation. Complication is introduced by the unknown and varying sensitivity of the procedure with population prevalence. The DeVlas model for the worm and egg distributions in the population describes how test sensitivity increases with age of the epidemic, as prevalence and intensity of infection increase, making the problem fundamentally different from earlier work in pooling. Previous literature discusses varying sensitivity with the number of positive samples within a pool, known as the “dilution effect.” We model both the dilution effect and varying sensitivity with population prevalence. For model parameter values suited to younger age groups, the pooled method has less than half the mean square error of the individualed method. Thus, we can use half as many slides while maintaining accuracy. Such savings might encourage more frequent measurements in regions where schistosomiasis is a serious but neglected problem.
Inhibitory Effects of Pepstatin A and Mefloquine on the Growth of Babesia Parasites
Authors: Munkhjargal Tserendorj , AbouLaila Mahmoud , Terkawi Mohamad Alaa , Sivakumar Thillaiampalam , Ichikawa Madoka , Davaasuren Batdorj , Nyamjargal Tserendorj , Yokoyama Naoaki , Igarashi Ikuo
Published: September 2012

We evaluated the inhibitory effects of pepstatin A and mefloquine on the in vitro and in vivo growths of Babesia parasites. The in vitro growth of Babesia bovis, B. bigemina, B. caballi, and B. equi was significantly inhibited (P < 0.05) by micromolar concentrations of pepstatin A (50% inhibitory concentrations = 38.5, 36.5, 17.6, and 18.1 μM, respectively) and mefloquine (50% inhibitory concentrations = 59.7, 56.7, 20.7, and 4 μM, respectively). Furthermore, both reagents either alone at a concentration of 5 mg/kg or in combinations (2.5/2.5 and 5/5 mg/kg) for 10 days significantly inhibited the in vivo growth of B. microti in mice. Mefloquine treatment was highly effective and the combination treatments were less effective than other treatments. Therefore, mefloquine may antagonize the actions of pepstatin A against babesiosis and aspartic proteases may play an important role in the asexual growth cycle of Babesia parasites.
The Dengue Virus Mosquito Vector Aedes aegypti at High Elevation in México
Authors: Lozano-Fuentes Saul , Hayden Mary H. , Welsh-Rodriguez Carlos , Ochoa-Martinez Carolina , Tapia-Santos Berenice , Kobylinski Kevin C. , Uejio Christopher K. , Zielinski-Gutierrez Emily , Monache Luca Delle , Monaghan Andrew J. , Steinhoff Daniel F. , Eisen Lars
Published: September 2012

México has cities (e.g., México City and Puebla City) located at elevations > 2,000 m and above the elevation ceiling below which local climates allow the dengue virus mosquito vector Aedes aegypti to proliferate. Climate warming could raise this ceiling and place high-elevation cities at risk for dengue virus transmission. To assess the elevation ceiling for Ae. aegypti and determine the potential for using weather/climate parameters to predict mosquito abundance, we surveyed 12 communities along an elevation/climate gradient from Veracruz City (sea level) to Puebla City (∼2,100 m). Ae. aegypti was commonly encountered up to 1,700 m and present but rare from 1,700 to 2,130 m. This finding extends the known elevation range in México by > 300 m. Mosquito abundance was correlated with weather parameters, including temperature indices. Potential larval development sites were abundant in Puebla City and other high-elevation communities, suggesting that Ae. aegypti could proliferate should the climate become warmer.
Mechanism of Anemia in Schistosoma mansoni–Infected School Children in Western Kenya
Authors: Butler Sara E. , Muok Erick M. , Montgomery Susan P. , Odhiambo Keziah , Mwinzi Pauline M. N. , Secor W. Evan , Karanja Diana M. S.
Published: September 2012

A better understanding of the mechanism of anemia associated with Schistosoma mansoni infection might provide useful information on how treatment programs are implemented to minimize schistosomiasis-associated morbidity and maximize treatment impact. We used a cross-sectional study with serum samples from 206 Kenyan school children to determine the mechanisms in S. mansoni-associated anemia. Serum ferritin and soluble transferrin receptor levels were measured by using an enzyme-linked immunosorbent assay. Results suggest that S. mansoni-infected persons are more likely (odds ratio = 3.68, 95% confidence interval = 1.33–10.1) to have levels of serum ferritin (> 100 ng/mL) that are associated with anemia of inflammation (AI) than S. mansoni-uninfected children. Our results suggest that AI is the most common form of anemia in S. mansoni infections. In contrast, the mechanism of anemia in S. mansoni-uninfected children was iron deficiency. Moreover, the prevalence of AI in the study participants demonstrated a significant trend with S. mansoni infection intensity (P < 0.001). Our results are consistent with those observed in S. japonicum-associated anemia.
Preventing Zoonotic Canine Leishmaniasis in Northeastern Brazil: Pet Attachment and Adoption of Community Leishmania Prevention
Authors: Esch Kevin J. , Pontes Nubia N. , Arruda Paulo , O'Connor Annette , Morais Lorena , Jeronimo Selma M. B. , Petersen Christine A.
Published: September 2012

Visceral leishmaniasis (VL), caused by Leishmania infantum chagasi (L.i. chagasi syn. infantum) in northeastern Brazil, was responsible for 51,000 new VL cases from 1980 to 2003. Household presence of L. infantum-infected dogs is a major risk factor for human infection. Despite culling of dogs based on seropositivity, canine L. infantum seroprevalence remains near 20%, suggesting that dog culling is ineffective for preventing VL spread. We administered a cross-sectional survey to 224 households within 300 m of the homes of VL human patients diagnosed within the last year. The goal was to develop a model for voluntary preventative use based on characteristics and motivations of dog owners. We identified that owner knowledge deficiencies regarding canine transmission of L. infantum associated with increased risk of dog infection (odds ratio [OR] = 3.681, confidence interval [CI] = 1.223, 11.08). Higher owner education was associated with decreased levels of dog seropositivity (OR = 0.40, CI = 0.20, 0.81). Pet attachment (P = 0.036) and perception of risk/disease knowledge (P = 0.040) were significantly associated with willingness to voluntarily purchase canine VL prevention. These results highlight the importance of owner attachment to their pet in implementing reservoir-targeted zoonotic VL prevention.
HTLV-1 and -2 Infections among 10 Indigenous Groups in the Peruvian Amazon
Authors: Alva Isaac E. , Orellana E. Roberto , Blas Magaly M. , Bernabe-Ortiz Antonio , Cotrina Armando , Chiappe Marina , Kochel Tadeusz J. , Carcamo Cesar P. , García Patricia J. , Zunt Joseph R. , Buffardi Anne L. , Montano Silvia M.
Published: September 2012

Infections with HTLV-1 and -2 were detected in 12 (1.9%) and 6 (0.9%) indigenous individuals living in 27 Amazonian villages in Peru. All infections occurred in Shipibo-Konibo people. HTLV was more common among participants living in villages distant from larger port cities and women with non-monogamous sexual partners.
Frequency of Reexposure to Vibrio cholerae O1 Evaluated by Subsequent Vibriocidal Titer Rise after an Episode of Severe Cholera in a Highly Endemic Area in Bangladesh
Authors: Weil Ana A. , Chowdhury Fahima , Khan Ashraful I. , Leung Daniel T. , Uddin Taher , Begum Yasmin Ara , Saha Nirod Chandra , Charles Richelle C. , LaRocque Regina C. , Harris Jason B. , Ryan Edward T. , Qadri Firdausi , Calderwood Stephen B.
Published: September 2012

Vibriocidal antibody is a marker of recent exposure to Vibrio cholerae O1 infection. We examined vibriocidal titers for 1 year after an episode of severe cholera in patients in Dhaka, Bangladesh; 16 of 53 (30%) patients had a fourfold or greater increase in vibriocidal titer between 6 and 12 months after an episode of severe cholera, suggesting reexposure to the organism. Among patients with rises in titers during follow-up, the patients initially infected with serotype Ogawa had earlier rises in titer than the patients initially infected with serotype Inaba. These data and others suggest that an episode of severe cholera protects against symptomatic disease for several years, but reexposure to the organism occurs frequently in an endemic area, with immunological boosts beginning as early as 6 months after severe disease. Repeated exposures to V. cholerae in endemic areas may be a necessary component for long-lasting protection against severe disease.
The Impact of Preparing Agriculture Faculty to Influence Student Critical Thinking Disposition
Authors: Burbach Mark E. , Matkin Gina S. , Quinn Courtney E. , Searle Travis P.
Published: September 2012

This study examined the effect of agriculture faculty training in and practice of methodologies to explicitly teach critical thinking skills related to course content and subsequent change in student critical thinking disposition. Twelve instructors in 14 agriculture courses underwent a year–long program of instruction in effective critical thinking development. Students completed the University of Florida– Engagement, Maturity, and Innovativeness assessment (UF–EMI) at the beginning and the end of the semester. Pair–wise comparisons showed significant increases in all three critical thinking dispositions (i.e., engagement, cognitive maturity, and innovativeness). In addition, a step–wise regression on the data gathered at the end of the semester showed that grade point average was positively related to all three critical thinking dispositions and being in one's first year of college was negatively related to each dimension. The 300 course level was negatively related to innovativeness and engagement. Being in the second and third year of college were also negatively related to engagement. This study supports the notion that instructors can influence students’ critical thinking disposition within the limited time of a college semester.
Assessing the Effect of Using a Science–Enhanced Curriculum to Improve Agriculture Students’ Science Scores: A Causal Comparative Study
Authors: Haynes J. Chris , Robinson J. Shane , Edwards M. Craig , Key James P.
Published: September 2012

The academic skills of today’s teenagers are diminishing, and are a cause for concern. One of the academic areas in need of improvement is science. The purpose of this causal comparative study was to determine the effect that a science–enhanced, curriculum would have on students’ achievement in science. The population for this study consisted of students in secondary agricultural education programs whose instructors held a science credential in Oklahoma during the 2009–2010 school year and were selected by state staff in the Agricultural Education Division of the Oklahoma Career and Technology Education Department to teach the science–enhanced, curriculum. In addition, 10 equally credentialed instructors formed a purposeful comparison group and were selected according to specific variables (e.g., similarity of students’ SES status) for equivalency purposes. The findings of this study revealed that a statistically significant difference in students’ science achievement did not exist as a result of the treatment. However, small practical differences were detected between the groups, as student performance in the treatment group was more than two and one–half points higher than the means of students’ performance scores in the comparison group. Recommendations point to the need for replication of the study over an entire school year.
Effects of Inquiry–based Agriscience Instruction and Subject Matter–based Instruction on Student Argumentation Skills
Authors: Thoron Andrew C. , Myers Brian E.
Published: September 2012

The purpose of this study was to determine the effect of inquiry–based agriscience instruction on student argumentation skills. Argumentation is defined as the student’s ability to establish a claim, provide a rationale for steps taken, provide and justify data, recognize alternate conclusions, and provide evidence why the conclusion is correct or the best solution. Developing argumentation skills can aid in developing the next generation of scientists, and help individuals who are not scientists, distinguish evidence from bias. This quasi–experimental study investigated the effect of two teaching methods on student argumentation skills. Inquiry–based instruction was compared to the subject matter approach in 15 agriscience education classes in seven secondary schools across the United States. Univariate analysis of covariance, detected a statistically significant difference between groups on argumentation skills. Those students taught through inquiry–based instruction had higher argumentation skill than students taught through the subject matter approach.
Factors Influencing or Discouraging Secondary School Students’ FFA Participation
Authors: Phelps Kirstin , Henry Anna L. , Bird William A.
Published: September 2012

Modern adolescents are faced with a variety of choices regarding how to spend their free time. As recruitment and increased student participation continues to be a major priority of the National FFA Organization, it is essential to explore the reasons why students make the choice to become or not to become a member of FFA. This study was a part of a larger, collective case study of members and non– members in school–based agricultural education programs located in ten small town, rural, and urban fringe schools across Illinois. The purpose of the study was to explore what influences students’ decision to join or not join the National FFA Organization. Students in this collective case study participated in semi–structured focus group interviews, individual interviews, and completed questionnaires. Four themes emerged as reasons to join FFA and three themes emerged as major reasons non–members elected not to participate in the FFA. Implications and recommendations concerning marketing of and recruitment for FFA programs were discussed.
Technology Acceptance Related to Second Life™, Social Networking, Twitter™, and Content Management Systems: Are Agricultural Students Ready, Willing, and Able?
Authors: Murphrey Theresa Pesl , Rutherford Tracy A. , Doerfert David L. , Edgar Leslie D. , Edgar Don W.
Published: September 2012

Technology has the potential to improve education but only if it is applied with purpose and consideration of the audience. Understanding technology’s role in education goes beyond the comparison of tools; there is a need to better understand student acceptance of technology so appropriate educational scaffolding and support can be provided. The absence of technology acceptance can become a barrier to the adoption, successful implementation, and use of new technologies. Therefore, the theoretical framework was based on technology acceptance. Described in this study is agricultural students’ acceptance and readiness to use specific technologies (i.e., Second Life™, social networking, Twitter™, and content management systems) as educational tools. The population was all students enrolled in eight courses at Texas A&M University during the Fall 2010 semester. A total of 716 completed surveys were analyzed. Findings revealed that students perceive each of the technologies studied (i.e., Second Life™, social networking, Twitter™, and content management systems) as unique entities that vary in regard to acceptance. Students overwhelmingly accept content management systems as a useful educational technology while Second Life™, Twitter™, and social networking are familiar but not as accepted. Findings reinforce the importance of instructors finding specific methods to successfully implement technology–specific educational tools.
The Effect of Teacher Demographic and Personal Characteristics on Perceptions of Diversity Inclusion in Agricultural Education Programs
Authors: LaVergne Douglas D. , Jones Wash A. , Larke Alvin , Elbert Chanda D.
Published: September 2012

Agricultural education teachers’ attitudes about the perceptions of diversity inclusion in their programs are variables that may have a strong influence on the number of students that enroll in agricultural education. This study examines the effect of teachers’ demographic and personal characteristics on their perceptions of the benefits of diversity inclusion, perceived barriers to diversity inclusion, and proposed solutions to increase diversity inclusion in agricultural education programs. Using a web–based questionnaire, the researchers employed a nonproportional stratified random sampling technique and 232 agricultural education teachers participated in the study. Through comparative analysis, researchers found statistically significant differences existed in teachers’ perceptions toward the benefits of diversity inclusion, the perceived barriers toward diversity inclusion, and the proposed solutions to increase diversity inclusion in agricultural education programs. Additional research should be conducted to understand better why these differences exist.
Investigating Students’ Satisfaction with eLearning Courses: The Effect of Learning Environment and Social Presence
Authors: Strong Robert , Irby Travis L. , Wynn J. Thomas , McClure Megan M.
Published: September 2012

Student demand and budget shortages have influenced the need for land–grant institutions to offer online courses. Research has identified that online courses broaden the reach of land–grant institutions to students who may not have access to campus. Literature indicated student satisfaction in online courses should be routinely assessed in order to potentially improve online course delivery. This study was framed with the motivational needs theory and social presence theory. The purpose of this study was to measure students’ perceptions of the learning environment, social presence, and satisfaction in online courses. An electronic survey was implemented using the Tailored Design Method to collect the data. Learning environment was correlated with social presence, and learning environment and social presence were significant effects on students’ satisfaction p < .05. Learning environment and social presence accounted for 26% of the variance in students’ satisfaction with eLearning courses. Including social media tools in eLearning courses, may assist students enhance their social presence in the respective course. Designing types of assignments that involve collaboration among students, and instituting authentic learning experiences that align with student interests, will improve students’ social presence, the learning environment and student satisfaction in eLearning courses.
Undergraduate Involvement in Extracurricular Activities and Leadership Development in College of Agriculture and Life Sciences Students
Authors: Foreman Elizabeth A. , Retallick Michael S.
Published: September 2012

The purpose of this study was to identify and describe experiences of undergraduate extracurricular involvement that result in increased leadership development. Senior students in the College of Agriculture and Life Sciences at Iowa State University completed an online questionnaire about their extracurricular experiences. Leadership development was conceptualized using the social change model. The Socially Responsible Leadership Scale (SRLS–R2) group scale was used to access leadership group values, and the Omnibus SRLS–R2 was used to measure the overall leadership construct. Ninety–six percent of respondents indicated they were involved in an extracurricular activity, including 21% in the Greek system, 95% in clubs and organizations, and 29% in competitive teams. Students who reported serving as an officer of a club or organization and students who reported spending more hours per week in extracurricular clubs and organizations scored significantly higher on both the SRLS–R2 group and an Omnibus SRLS score.
Systematic variations of cloud top temperature and precipitation rate with aerosols over the global tropics
Authors: Niu Feng , Li Zhanqing
Published: September 2012

Abstract. Aerosols may modify cloud properties and precipitation via a variety of mechanisms with varying and contradicting consequences. Using a large ensemble of satellite data acquired by the Moderate Resolution Imaging Spectroradiometer onboard the Earth Observing System's Aqua platform, the CloudSat cloud profiling radar and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite over the tropical oceans, we identified two distinct correlations of clouds and precipitation with aerosol loading. Cloud-top temperatures are significantly negatively correlated with increasing aerosol index (AI) over oceans and aerosol optical depth (AOT) over land for deep mixed-phase clouds with liquid droplets near the warm bases and ice crystals near the cold tops; no significant changes were found for uniformly liquid clouds. Precipitation rates are positively correlated with the AI for mixed-phase clouds, but negatively correlated for liquid clouds. These distinct correlations might be a manifestation of two potential mechanisms: the invigoration effect (which enhances convection and precipitation) and the microphysical effect (which suppresses precipitation). We note that the highly limited information garnered from satellite products cannot unequivocally support the causal relationships between cloud-top temperature/precipitation rate and aerosol loading. But if aerosols are indeed the causes for the observed relationships, they may change the overall distribution of precipitation, leading to a more extreme and unfavorable rainfall pattern of suppressing light rains and fostering heavy rains.
Modelling of organic aerosols over Europe (2002–2007) using a volatility basis set (VBS) framework: application of different assumptions regarding the formation of secondary organic aerosol
Authors: Bergström R. , Denier van der Gon H. A. C. , Prévôt A. S. H. , Yttri K. E. , Simpson D.
Published: September 2012

Abstract. A new organic aerosol module has been implemented into the EMEP chemical transport model. Four different volatility basis set (VBS) schemes have been tested in long-term simulations for Europe, covering the six years 2002–2007. Different assumptions regarding partitioning of primary organic aerosol and aging of primary semi-volatile and intermediate volatility organic carbon (S/IVOC) species and secondary organic aerosol (SOA) have been explored. Model results are compared to filter measurements, aerosol mass spectrometry (AMS) data and source apportionment studies, as well as to other model studies. The present study indicates that many different sources contribute significantly to organic aerosol in Europe. Biogenic and anthropogenic SOA, residential wood combustion and vegetation fire emissions may all contribute more than 10% each over substantial parts of Europe. This study shows smaller contributions from biogenic SOA to organic aerosol in Europe than earlier work, but relatively greater anthropogenic SOA. Simple VBS based organic aerosol models can give reasonably good results for summer conditions but more observational studies are needed to constrain the VBS parameterisations and to help improve emission inventories. The volatility distribution of primary emissions is one important issue for further work. Emissions of volatile organic compounds from biogenic sources are also highly uncertain and need further validation. We can not reproduce winter levels of organic aerosol in Europe, and there are many indications that the present emission inventories substantially underestimate emissions from residential wood combustion in large parts of Europe.
Technical Note: Synthesis of isoprene atmospheric oxidation products: isomeric epoxydiols and the rearrangement products cis- and trans-3-methyl-3,4-dihydroxytetrahydrofuran
Authors: Zhang Z. , Lin Y.-H. , Zhang H. , Surratt J. D. , Ball L. M. , Gold A.
Published: September 2012

Abstract. Isoprene epoxydiol (IEPOX) isomers are key gas-phase intermediates of isoprene atmospheric oxidation. Secondary organic aerosols derived from such intermediates have important impacts on air quality and health. We report here convergent and unambiguous pathways developed for the synthesis of isomeric IEPOX species and the rearrangement products cis- and trans-3-methyl-3,4-dihydroxytetrahydrofuran in good yield. The availability of such compounds is necessary to expedite research on isoprene atmospheric oxidation mechanisms and subsequent aerosol formation as well as the toxicological properties of the aerosols.
Factor analysis of combined organic and inorganic aerosol mass spectra from high resolution aerosol mass spectrometer measurements
Authors: Sun Y. L. , Zhang Q. , Schwab J. J. , Yang T. , Ng N. L. , Demerjian K. L.
Published: September 2012

Abstract. Positive matrix factorization (PMF) was applied to the merged high resolution mass spectra of organic and inorganic aerosols from aerosol mass spectrometer (AMS) measurements to investigate the sources and evolution processes of submicron aerosols in New York City in summer 2009. This new approach is able to study the distribution of organic and inorganic species in different types of aerosols, the acidity of organic aerosol (OA) factors, and the fragment ion patterns related to photochemical processing. In this study, PMF analysis of the unified AMS spectral matrix resolved 8 factors. The hydrocarbon-like OA (HOA) and cooking OA (COA) factors contain negligible amounts of inorganic species. The two factors that are primarily ammonium sulfate (SO4-OA) and ammonium nitrate (NO3-OA), respectively, are overall neutralized. Among all OA factors the organic fraction of SO4-OA shows the highest degree of oxidation (O/C = 0.69). Two semi-volatile oxygenated OA (OOA) factors, i.e., a less oxidized (LO-OOA) and a more oxidized (MO-OOA), were also identified. MO-OOA represents local photochemical products with a diurnal profile exhibiting a pronounced noon peak, consistent with those of formaldehyde (HCHO) and Ox(= O3 + NO2). The NO+/NO2+ ion ratio in MO-OOA is much higher than that in NO3-OA and in pure ammonium nitrate, indicating the formation of organic nitrates. The nitrogen-enriched OA (NOA) factor contains ~25% of acidic inorganic salts, suggesting the formation of secondary OA via acid-base reactions of amines. The size distributions of OA factors derived from the size-resolved mass spectra show distinct diurnal evolving behaviors but overall a progressing evolution from smaller to larger particle mode as the oxidation degree of OA increases. Our results demonstrate that PMF analysis of the unified aerosol mass spectral matrix which contains both inorganic and organic aerosol signals may enable the deconvolution of more OA factors and gain more insights into the sources, processes, and chemical characteristics of OA in the atmosphere.
Model evaluation of marine primary organic aerosol emission schemes
Authors: Gantt B. , Johnson M. S. , Meskhidze N. , Sciare J. , Ovadnevaite J. , Ceburnis D. , O'Dowd C. D.
Published: September 2012

Abstract. In this study, several marine primary organic aerosol (POA) emission schemes have been evaluated using the GEOS-Chem chemical transport model in order to provide guidance for their implementation in air quality and climate models. These emission schemes, based on varying dependencies of chlorophyll a concentration ([chl a]) and 10 m wind speed (U10), have large differences in their magnitude, spatial distribution, and seasonality. Model comparison with weekly and monthly mean values of the organic aerosol mass concentration at two coastal sites shows that the source function exclusively related to [chl a] does a better job replicating surface observations. Sensitivity simulations in which the negative U10 and positive [chl a] dependence of the organic mass fraction of sea spray aerosol are enhanced show improved prediction of the seasonality of the marine POA concentrations. A top-down estimate of submicron marine POA emissions based on the parameterization that compares best to the observed weekly and monthly mean values of marine organic aerosol surface concentrations has a global average emission rate of 6.3 Tg yr−1. Evaluation of existing marine POA source functions against a case study during which marine POA contributed the major fraction of submicron aerosol mass shows that none of the existing parameterizations are able to reproduce the hourly-averaged observations. Our calculations suggest that in order to capture episodic events and short-term variability in submicron marine POA concentration over the ocean, new source functions need to be developed that are grounded in the physical processes unique to the organic fraction of sea spray aerosol.
The Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS): model description and application to a temperate deciduous forest canopy
Authors: Saylor R. D.
Published: September 2012

Abstract. Forest canopies are primary emission sources of biogenic volatile organic compounds (BVOCs) and have the potential to significantly influence the formation and distribution of secondary organic aerosol (SOA) mass. Biogenically-derived SOA formed as a result of emissions from the widespread forests across the globe may affect air quality in populated areas, degrade atmospheric visibility, and affect climate through direct and indirect forcings. In an effort to better understand the formation of SOA mass from forest emissions, a 1-D column model of the physical and chemical processes occurring within and just above a vegetative canopy has been created. This model, the Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS), includes processes accounting for the emission of BVOCs from the canopy, turbulent vertical transport within and above the canopy and throughout the height of the planetary boundary layer (PBL), near-explicit representation of chemical transformations, mixing with the background atmosphere and bi-directional exchange between the atmosphere and canopy and the atmosphere and forest floor. The model formulation of ACCESS is described in detail and results are presented for an initial application of the modeling system to Walker Branch Watershed, an isoprene-emission-dominated forest canopy in the Southeastern United States which has been the focal point for previous chemical and micrometeorological studies. Model results of isoprene profiles and fluxes are found to be consistent with previous measurements made at the simulated site and with other measurements made in and above mixed deciduous forests in the Southeastern United States. Sensitivity experiments exploring how canopy concentrations and fluxes of gas-phase precursors of SOA are affected by background anthropogenic nitrogen oxides suggest potentially significant non-linearities in the chemical and physical system of the canopy which may have an impact on the relative magnitude of SOA formed through aqueous- versus gas-phase pathways as a function of anthropogenic influence.
On the export of reactive nitrogen from Asia: NOx partitioning and effects on ozone
Authors: Bertram T. H. , Perring A. E. , Wooldridge P. J. , Dibb J. , Avery M. A. , Cohen R. C.
Published: September 2012

Abstract. The partitioning of reactive nitrogen (NOy) was measured over the remote North Pacific during spring 2006. We use these observations to assess the impact of increasing emissions of nitrogen oxides in East Asia on ozone (O3) production rates over the remote Pacific and the intercontinental transport of O3 and its precursors to North America. Aircraft observations of speciated NOy, made between 25° and 55° N, confirm a controlling role for peroxyacyl nitrates in NOx production in aged Asian outflow, accounting for more than 60% of NOy above 5 km, while thermal dissociation limits their contribution to less than 10% in the lower troposphere. The observations reveal the extreme sensitivity of the remote Pacific to future changes in NOx loadings, with an experimentally determined crossover point between net Oxdestruction and net Ox production of 60 pptv NOx. Using simultaneous observations of speciated NOy and wind speed, we calculate the flux of reactive nitrogen through the meridional plane of 150° W (between 25° and 55° N) to be 0.007 ± 0.002 Tg N day−1, which provides an upper limit of 15% on the export efficiency of NOy from East Asia. Analysis of the subsiding plumes in the sampling domains suggests that episodic dry subsidence events play an important role in the intercontinental transport of ozone and its precursors from East Asia to North America.
The effects of recent control policies on trends in emissions of anthropogenic atmospheric pollutants and CO2 in China
Authors: Zhao Y. , Zhang J. , Nielsen C. P.
Published: September 2012

Abstract. To examine the effects of China's national policies of energy conservation and emission control during 2005–2010, inter-annual emission trends of gaseous pollutants, primary aerosols, and CO2 are estimated with a bottom-up framework. The control measures led to improved energy efficiency and/or increased penetration of emission control devices at power plants and other important industrial sources, yielding reduced emission factors for all evaluated species except NOx. The national emissions of anthropogenic SO2, CO, and total primary PM (particulate matter) in 2010 are estimated to have been 89%, 108%, and 86% of those in 2005, respectively, suggesting successful emission control of those species despite fast growth of the economy and energy consumption during the period. The emissions of NOx and CO2, however, are estimated to have increased by 48% and 43%, respectively, indicating that they remain largely determined by the growth of energy use, industrial production, and vehicle populations. Based on application of a Monte-Carlo framework, estimated uncertainties of SO2 and PM emissions increased from 2005 to 2010, resulting mainly from weakly understood average SO2 removal efficiency in flue gas desulfurization (FGD) systems in the power sector, and unclear changes in the penetration levels of dust collectors at industrial sources, respectively. While emission trends determined by bottom-up methods can be generally verified by observations from both ground stations and satellites, clear discrepancies exist for given regions and seasons, indicating a need for more accurate spatial and time distributions of emissions. Limitations of current emission control polices are analyzed based on the estimated emission trends. Compared with control of total PM, there are fewer gains in control of fine particles and carbonaceous aerosols, the PM forms most responsible for damages to public health and effects on radiative forcing. A decrease of alkaline base cations as primary PM that is much faster than that of SO2 may have raised the acidification risks to ecosystems, indicating further control of acid precursors is required. Moreover, with relatively strict controls in developed urban areas, air pollution challenges have been expanding to less-developed neighboring regions. There is a great need in the future for multi-pollutant control strategies that combine recognition of diverse environmental impacts both in urban and rural areas with emission abatement of multiple species in concert.
Characteristics of atmospheric total gaseous mercury (TGM) observed in urban Nanjing, China
Authors: Zhu J. , Wang T. , Talbot R. , Mao H. , Hall C. B. , Yang X. , Fu C. , Zhuang B. , Li S. , Han Y. , Huang X.
Published: September 2012

Abstract. Long-term continuous measurements of total gaseous mercury (TGM = gaseous elemental mercury (GEM) + reactive gaseous mercury, RGM) were conducted simultaneously along with meteorological variables and a suite of trace gases at an urban site in Nanjing, China from 18 January to 31 December 2011. Measurements were conducted using a high resolution mercury vapor analyzer (Tekran 2537B) with 5-min time resolution. The average concentration of TGM was 7.9 ± 7.0 ng m−3 with a range of 0.8–180 ng m−3 over the study period. TGM concentrations followed a typical lognormal pattern dominated by a range of 3–7 ng m−3, which was significantly higher than the continental background values (~1.5 ng m−3) in Northern Hemisphere. The mean seasonal TGM concentrations decreased in the following order: summer, spring, fall, and winter. This seasonal pattern was quite different from measurements at most other sites around the world. We attributed high monthly average concentrations to the re-volatilization of deposited mercury during the warm season due to high temperatures and greater solar radiation. Previous Modeling studies suggested that Nanjing and the surrounding region have the largest Chinese natural emissions during the summer. Positive correlations between temperature, solar radiation, and TGM concentration combined with no correlation between CO and TGM in summer provide a strong indication that natural sources are important in Nanjing. While most sharp peaks were caused by anthropogenic sources. TGM concentrations in Nanjing exhibited a noticeable diurnal pattern with a sharp increase after sunrise and peak of greater than 8 m−3 during 7–10 a.m. LT. Further, seasonally averaged diurnal cycles of TGM exhibited considerably different patterns with the largest variation in spring and insignificant fluctuations in winter. Using HYSPLIT backwards trajectories from six clusters, it was indicated that the highest TGM concentrations, 11.9 m−3, was derived from lacal air masses. The cleanest air masses, with an average TGM concentration of 4.7 and 5.9 m−3, were advected from the north via fast transport facilitated by sweeping synoptic flows.
Potential of the future thermal infrared space-borne sensor IASI-NG to monitor lower tropospheric ozone
Authors: Sellitto P. , Dufour G. , Eremenko M. , Cuesta J. , Dauphin P. , Forêt G. , Gaubert B. , Beekmann M. , Peuch V.-H. , Flaud J.-M.
Published: September 2012

Abstract. The lower tropospheric (LT) ozone concentration is a key factor for air quality (AQ). Observing efficiently LT ozone from space is crucial to monitor and better understand pollution phenomena occurring from inter-continental to local scales, and that have a proven noxious effect on the human health and the biosphere. The Infrared Atmospheric Sounder Interferometer (IASI) flies on MetOp-A spacecraft and is planned to be launched in the next future as part of the other MetOp modules, i.e. MetOp-B and C. IASI has demonstrated to have the capability to single out the LT ozone signal only at favourable conditions, i.e. in presence of high thermal contrast scenarios. New generation satellite instruments are being designed to address several pressing geophysical issues, including a better observation capability of LT ozone. IASI-NG (New Generation), now having reached the accomplishment of design phase-A for launch in the 2020 timeframe as part of the EPS-SG (EUMETSAT Polar System-Second Generation, formerly post-EPS) mission, may render feasible a better observation of AQ in terms of LT ozone. To evaluate the added-value brought by IASI-NG in this context, we developed a pseudo-observation simulator, including a direct simulator of thermal infrared spectra and a full inversion scheme to retrieve ozone concentration profiles. We produced one month (August 2009) of tropospheric ozone pseudo-observations based on both IASI and IASI-NG instrumental configurations. We compared the pseudo-observations and we found a clear improvement of LT ozone (up to 6 km altitude) pseudo-observations quality for IASI-NG. The estimated total error is expected to be more than 35% smaller at 5 km, and 20% smaller for the LT ozone column. The total error on the LT ozone column is, on average, lower than 10% for IASI-NG. IASI-NG is expected to have a significantly better vertical sensitivity (monthly average degrees of freedom surface-6 km of 0.70) and to be sensitive at lower altitudes (more than 0.5 km lower than IASI, reaching values of nearly 3.0 km). Vertical ozone layers of 4 to 5 km thickness are expected to be resolved by IASI-NG, while IASI has a vertical resolution of 6–8 km. According to our analyses, IASI-NG is expected to have the possibility of effectively separate lower from upper tropospheric ozone information even for low sensitivity scenarios. In addition, IASI-NG is expected to be able to better monitor LT ozone patterns at local spatial scale and to monitor abrupt temporal evolutions occurring at time-scales of a few days, thus bringing an expected added-value with respect to IASI for the monitoring of AQ.
Storage and stability of organic carbon in soils as related to depth, occlusion within aggregates, and attachment to minerals
Authors: Schrumpf M. , Kaiser K. , Guggenberger G. , Persson T. , Kögel-Knabner I. , Schulze E.-D.
Published: September 2012

Abstract. Conceptual models suggest that stability and age of organic carbon (OC) in soil depends on the source of plant litter, occlusion within aggregates, incorporation in organo-mineral complexes, and location within the soil profile. Various tools like density fractionation, mineralization experiments, and radiocarbon analyses have been used to study the importance of these mechanisms. We systematically apply them to a range of European soils to test whether general controls emerge even for soils that vary in vegetation, soil types, parent material, and land use. At each of the 12 study sites, 10 soil cores were sampled in 10 cm depth intervals to 60 cm depth and subjected to density separation. Bulk soil samples and density fractions (free light fractions – fLF, occluded light fractions – oLF, heavy fractions – HF) were analysed for OC, total nitrogen (TN), δ13C, and Δ14C. Bulk samples were also incubated to determine mineralizable OC. Declining OC-normalized CO2 release and increasing age with soil depth confirm greater stability of OC in subsoils across sites. Depth profiles of LF-OC matched those of roots, which in turn reflect plant functional types in soil profiles not subject to ploughing. Modern Δ14C signatures and positive correlation between mineralizable C and fLF-OC indicate the fLF is an easily available energy and nutrient source for subsurface microbes. Fossil C derived from the geogenic parent material affected the age of OC especially in the LF at three study sites. The overall importance of OC stabilization by binding to minerals was demonstrated by declining OC-normalized CO2 release rates with increasing contributions of HF-OC to bulk soil OC and the low Δ14C values of HF-OC. The stability of HF-OC was greater in subsoils than in topsoils; nevertheless, a portion of HF-OC was active throughout the profile. The decrease in Δ14C (increase in age) of HF-OC with soil depth was related to soil pH as well as to dissolved OC fluxes. This indicates that dissolved OC translocation contributes to the formation of subsoil HF-OC and shapes the Δ14C profiles. While quantitatively less important than OC in the HF, consistent older ages of oLF-OC than fLF-OC indicate that occlusion of LF-OC in aggregates also contributes to OC stability in subsoils. Overall, our results showed that association with minerals is the most important factor in stabilization of OC in soils.