Simultaneous measurements of particulate and gas-phase water-soluble organic carbon concentrations at remote and urban-influenced locations

The sources, sinks, and overall importance of watersoluble organic carbon (WSOC) in the atmosphere are not well understood. Although the primary historical focus has been on particulate WSOC (WSOCP), here we also present results obtained using a newly developed technique that additionally measures gas-phase water-soluble organic carbon (WSOCG). These first-of-their-kind measurements show that WSOCG can often be more than ten times larger than WSOCP at both urban and remote locations. The average fraction of WSOC residing in the gas phase (fg = WSOCG/(WSOCG + WSOCP)) at five various field sites ranged from 0.64 to 0.93, implying significant differences in WSOC phase partitioning between locations. At Houston, TX, and Summit, Greenland, a repeatable diurnal pattern was observed, with minimum values for fg occurring at night. These trends likely are due, at least in part, to temperature and/or relative humidity related gas-to-particle partitioning. These coincident measurements of WSOC in both the gas and particle phases indicate that a relatively large reservoir of water-soluble organic mass is not taken into account by measurements focused only on WSOCP. In addition, a significant amount of WSOCG is available to form WSOCP or enter cloud droplets depending on the chemical and physical properties of the droplets and/or aerosols present. Citation: Anderson, C., J. E. Dibb, R. J. Griffin, and M. H. Bergin (2008), Simultaneous measurements of particulate and gas-phase water-soluble organic carbon concentrations at remote and urban-influenced locations, Geophys. Res. Lett., 35, L13706, doi:10.1029/2008GL033966

Implementation of a Direct-Imaging and FX Correlator for the BEST-2 Array

A new digital backend has been developed for the BEST-2 array at Radiotelescopi di Medicina, INAF-IRA, Italy which allows concurrent operation of an FX correlator, and a direct-imaging correlator and beamformer. This backend serves as a platform for testing some of the spatial Fourier transform concepts which have been proposed for use in computing correlations on regularly gridded arrays. While spatial Fourier transform-based beamformers have been implemented previously, this is to our knowledge, the first time a direct-imaging correlator has been deployed on a radio astronomy array. Concurrent observations with the FX and direct-imaging correlator allows for direct comparison between the two architectures. Additionally, we show the potential of the direct-imaging correlator for time-domain astronomy, by passing a subset of beams though a pulsar and transient detection pipeline. These results provide a timely verification for spatial Fourier transform-based instruments that are currently in commissioning. These instruments aim to detect highly-redshifted hydrogen from the Epoch of Reionization and/or to perform widefield surveys for time-domain studies of the radio sky. We experimentally show the direct-imaging correlator architecture to be a viable solution for correlation and beamforming.Comment: 12 pages, 17 figures, 2 tables, Accepted to MNRAS January 24, 2014, includes appendix diagram

Influential Article Review - Innovation and Business Outsourcing in Tunisia

This paper examines innovation. We present insights from a highly influential paper. Here are the highlights from this paper: Recently, outsourcing services has been an important component of the organizational strategy of service firms. However, most research studies mainly focus on analyzing the determining factors of outsourcing at the expense of its structural effects. The aim of this paper is to examine the extent to which outsourcing relationships can be a source of service innovation by using a sample of 108 Tunisian service firms. Specifically, we are interested in the domestic outsourcing of auxiliary activities. Our results support the evidence of positive effects of outsourcing service activities on the capacity of innovation. This suggests that outsourcing allows Tunisian service firms to create value, increase flexibility and improve the quality of their services. For our overseas readers, we then present the insights from this paper in Spanish, French, Portuguese, and German

Benefits of Using a Mars Forward Strategy for Lunar Surface Systems

This paper identifies potential risk reduction, cost savings and programmatic procurement benefits of a Mars Forward Lunar Surface System architecture that provides commonality or evolutionary development paths for lunar surface system elements applicable to Mars surface systems. The objective of this paper is to identify the potential benefits for incorporating a Mars Forward development strategy into the planned Project Constellation Lunar Surface System Architecture. The benefits include cost savings, technology readiness, and design validation of systems that would be applicable to lunar and Mars surface systems. The paper presents a survey of previous lunar and Mars surface systems design concepts and provides an assessment of previous conclusions concerning those systems in light of the current Project Constellation Exploration Architectures. The operational requirements for current Project Constellation lunar and Mars surface system elements are compared and evaluated to identify the potential risk reduction strategies that build on lunar surface systems to reduce the technical and programmatic risks for Mars exploration. Risk reduction for rapidly evolving technologies is achieved through systematic evolution of technologies and components based on Moore's Law superimposed on the typical NASA systems engineering project development "V-cycle" described in NASA NPR 7120.5. Risk reduction for established or slowly evolving technologies is achieved through a process called the Mars-Ready Platform strategy in which incremental improvements lead from the initial lunar surface system components to Mars-Ready technologies. The potential programmatic benefits of the Mars Forward strategy are provided in terms of the transition from the lunar exploration campaign to the Mars exploration campaign. By utilizing a sequential combined procurement strategy for lunar and Mars exploration surface systems, the overall budget wedges for exploration systems are reduced and the costly technological development gap between the lunar and Mars programs can be eliminated. This provides a sustained level of technological competitiveness as well as maintaining a stable engineering and manufacturing capability throughout the entire duration of Project Constellation

EPIDEMIOLOGICAL, GEOSPATIAL, AND PHYLOGENETIC EVIDENCE TO INFORM ACUTE HIV INFECTION DETECTION IN LILONGWE, MALAWI

The first few months of HIV infection are characterized by elevated viral loads and increased transmissibility, especially during the 4–6-week pre-seroconversion or “acute” phase. Detection of acute HIV infection (AHI) requires RNA or antigen testing, which is difficult to implement in many settings; however, sexually transmitted infections (STI) clinics have been consistently high-yield settings for AHI detection in Africa. The iKnow study, conducted between 2015 and 2019 at Bwaila STI clinic in Lilongwe, Malawi, constructed the largest single-site sample of people with AHI in Africa. Using survey, household locational, and viral genetic data from iKnow, we aimed to: 1) increase the efficiency of AHI detection at the STI clinic through sex-stratified risk score algorithms for identifying those most likely to benefit from AHI testing, 2) inform the potential expansion of AHI testing outside of the STI clinic through the development of a causal framework for HIV incidence and clinic attendance, and 3) evaluate the presence of geographic and phylogenetic clustering of AHI to inform tailored interventions in Lilongwe. The highest-performing risk-score algorithm for male clinic attendees included acute retroviral syndrome symptoms, genital sores/ulcers, and condom use (AUC = 0.74), while the analogous algorithm for females included 15 variables (AUC = 0.81). Our causal framework and empirical data suggested that people experiencing STI symptoms, perceiving a higher risk of HIV acquisition, and residing in neighborhoods with greater HIV prevalence are likely overrepresented in the STI clinic versus the community, especially among people without HIV. We identified six geospatial clusters of AHI that comprised 1% of the populated clinic catchment area and 5% of the total population while capturing 38% of the residences of clinic attendees with AHI. We found eight two-person phylogenetic clusters; however, 67% of samples could not be sequenced. STI clinics are an efficient venue for AHI detection, which can be made more efficient with risk score algorithms to guide the selection of those most likely to have AHI for RNA/antigen testing. Increased similarities between people with AHI and without HIV in the clinic versus the community also suggest that characteristics, networks, and neighborhoods of all STI clinic attendees – not just those with HIV or AHI – could be useful to inform expanded AHI detection. Finally, the presence of geospatial AHI clusters suggests that spatially focused AHI detection programs could offer additional high-yield approaches for AHI identification in the community.Doctor of Philosoph

Lossy Compression applied to the Worst Case Execution Time Problem

Abstract Interpretation and Symbolic Model Checking are powerful techniques in the field of testing. These techniques can verify the correctness of systems by exploring the state space that the systems occupy. As this would normally be intractable for even moderately complicated systems, both techniques employ a system of using approximations in order to reduce the size of the state space considered without compromising on the reliability of the results. When applied to Real-time Systems, and in particular Worst Case Execution Time Estimation, Abstract Interpretation and Symbolic Model Checking are primarily used to verify the temporal properties of a system. This results in a large number of applications for the techniques, from verifying the properties of components to the values given variables may take. In turn, this results in a large problem area for researchers in devising the approximations required to reduce the size of the state space whilst ensuring the analysis remains safe. This thesis examines the use of Abstract Interpretation and Symbolic Model Checking, in particular focusing on the methods used to create approximations. To this end, this thesis introduces the ideas of Information Theory and Lossy Compression. Information Theory gives a structured framework which allows quantifying or valuing information. In other domains, Lossy Compression utilises this framework to achieve reasonably accurate approximations. However, unlike Abstract Interpretation or Symbolic Model Checking, lossy compression provides ideas on how one can find information to remove with minimal consequences. Having introduced lossy compression applications, this thesis introduces a generic approach to applying lossy compression to problems encountered in Worst Case Execution Time estimation. To test that the generic approach works, two distinct problems in Worst Case Execution Time estimation are considered. The first of these is providing a Must/May analysis for the PLRU cache; whilst common in usage, the logical complexity of a PLRU cache renders it difficult to analyse. The second problem is that of loop bound analysis, with a particular focus on removing the need for information supplied by annotations, due to the inherent unverifiability of annotations

Aerosol major ion record at Mount Washington

This study examined the seasonal cycles and regional-scale meteorological controls on the chemical properties of bulk aerosols collected from 1999 to 2004 at Mount Washington, the highest peak in the northeastern United States. The concentrations of NH4+ and SO42− peaked during summer months. The pattern for aerosol NO3− was more complicated with relatively high median concentrations characterizing spring and summer months, but with major elevated events occurring during fall, winter, and spring. The seasonal relationship between NH4+ and SO42− indicated that during warmer months a mixture of (NH4)2SO4 and NH4HSO4 was present, while it was mainly the latter in winter. More acidity and higher concentrations of the major species were generally associated with winds from the southwest and west sectors. The highest (≥95th percentile) concentrations of SO42− and NH4+ were associated with air mass transport from major upwind source regions in the Midwest and along the eastern seaboard. The ionic composition and seasonal cycle observed at Mount Washington were similar to those measured at other northeastern sites, but the range and average concentrations were much lower. These differences were exaggerated during wintertime. Included in this paper are several Eulerian case studies of SO2 conversion to SO42− during transit from Whiteface Mountain, New York, to Mount Washington. The calculations suggest a gas-phase SO2 oxidation rate of ∼1–2% per hour and demonstrate the possibility of using these two sites to investigate the chemical evolution of air masses as they move from Midwestern source regions to northern New England

Inferring Group Processes from Computer-Mediated Affective Text Analysis

Political communications in the form of unstructured text convey rich connotative meaning that can reveal underlying group social processes. Previous research has focused on sentiment analysis at the document level, but we extend this analysis to sub-document levels through a detailed analysis of affective relationships between entities extracted from a document. Instead of pure sentiment analysis, which is just positive or negative, we explore nuances of affective meaning in 22 affect categories. Our affect propagation algorithm automatically calculates and displays extracted affective relationships among entities in graphical form in our prototype (TEAMSTER), starting with seed lists of affect terms. Several useful metrics are defined to infer underlying group processes by aggregating affective relationships discovered in a text. Our approach has been validated with annotated documents from the MPQA corpus, achieving a performance gain of 74% over comparable random guessers