bluuebunny/crossref_metadata_2025 huggingface dataset:
Bayesian Disease Classification Using Copy Number Data
Authors: Guha Subharup , Ji Yuan , Baladandayuthapani Veerabhadran
Published: October 2014

DNA copy number variations (CNVs) have been shown to be associated with cancer development and progression. The detection of these CNVs has the potential to impact the basic knowledge and treatment of many types of cancers, and can play a role in the discovery and development of molecular-based personalized cancer therapies. One of the most common types of high-resolution chromosomal microarrays is array-based comparative genomic hybridization (aCGH) methods that assay DNA CNVs across the whole genomic landscape in a single experiment. In this article we propose methods to use aCGH profiles to predict disease states. We employ a Bayesian classification model and treat disease states as outcome, and aCGH profiles as covariates in order to identify significant regions of the genome associated with disease subclasses. We propose a principled two-stage method where we first make inferences on the underlying copy number states associated with the aCGH emissions based on hidden Markov model (HMM) formulations to account for serial dependencies in neighboring probes. Subsequently, we infer associations with disease outcomes, conditional on the copy number states, using Bayesian linear variable selection procedures. The selected probes and their effects are parameters that are useful for predicting the disease categories of any additional individuals on the basis of their aCGH profiles. Using simulated datasets, we investigate the method's accuracy in detecting disease category. Our methodology is motivated by and applied to a breast cancer dataset consisting of aCGH profiles assayed on patients from multiple disease subtypes.
Idiopathic Ventral Spinal Cord Herniation: An Increasingly Recognized Cause of Thoracic Myelopathy
Authors: Berg-Johnsen Jon , Ilstad Eivind , Kolstad Frode , Züchner Mark , Sundseth Jarle
Published: October 2014

Idiopathic spinal cord herniation (ISCH), where a segment of the spinal cord has herniated through a ventral defect in the dura, is a rarely encountered cause of thoracic myelopathy. The purpose of our study was to increase the clinical awareness of this condition by presenting our experience with seven consecutive cases treated in our department since 2005. All the patients developed pronounced spastic paraparesis or Brown-Séquard syndrome for several years (mean, 4.7 years) prior to diagnosis. MRI was consistent with a transdural spinal cord herniation in the mid-thoracic region in all the cases. The patients underwent surgical reduction of the herniated spinal cord and closure of the dural defect using an artificial dural patch. At follow-up, three patients experienced considerable clinical improvement, one had slight improvement, one had transient improvement, and two were unchanged. Two of the four patients with sphincter dysfunction regained sphincter control. MRI showed realignment of the spinal cord in all the patients. ISCH is probably a more common cause of thoracic myelopathy than previously recognized. The patients usually develop progressive myelopathy for several years before the correct diagnosis is made. Early diagnosis is important in order to treat the patients before the myelopathy has become advanced.
Randomized Controlled Trial to Compare Growth Parameters and Nutrient Adequacy in Children with Picky Eating Behaviors who Received Nutritional Counseling with or without an Oral Nutritional Supplement
Authors: Sheng Xiaoyang , Tong Meiling , Zhao Dongmei , Leung Ting Fan , Zhang Feng , Hays Nicholas P. , Ge John , Ho Wing Man , Northington Robert , Terry Donna L. , Yao Manjiang
Published: October 2014

In this study, changes in growth parameters and nutrient intake were compared in Chinese children (ages 30-60 months) with picky eating (PE) behaviors and weight-for-height ≤25th percentile, who were randomized to receive nutrition counseling alone (NC; n = 76) or with a nutritional milk supplement (NC + NS; n = 77) for 120 days. Increases in weight-for-height z-scores were significantly greater in the NC + NS group at days 30 and 90 and over the entire study period (all P < 0.05), but not at day 120. Increases in weight-for-age z-scores were significantly greater in the NC + NS group at day 90 ( P = 0.025) and over the entire study period ( P = 0.046). Mean intakes of energy, protein, carbohydrate, docosahexaenoic acid, arachidonic acid, calcium, phosphorous, iron, zinc, and vitamins A, C, D, E, and B6 were significantly higher in the NC + NS group at days 60 and 120 (all P < 0.01). Thus, in young children with PE behaviors, nutritional supplementation given as an adjunct to NC resulted in greater improvements in nutrient intake compared with NC alone. Growth parameters differed between groups at several timepoints during the study, but not at day 120.
Predictors of Staff Turnover and Turnover Intentions within Addiction Treatment Settings: Change over Time Matters
Authors: Garner Bryan R. , Hunter Brooke D.
Published: October 2014

This study examined the extent to which changes over time in clinicians’ responses to measures of work attitude (eg, job satisfaction) and psychological climate (eg, supervisor support) could predict actual turnover and turnover intentions above and beyond absolute levels of these respective measures. Longitudinal data for this study were collected from a sample of clinicians ( N = 96) being trained to implement an evidence-based treatment for adolescent substance use disorders. Supporting findings from a recent staff turnover study, we found job satisfaction change was able to predict actual turnover above and beyond average levels of job satisfaction. Representing new contributions to the staff turnover literature, we also found that change over time in several other key measures (eg, job satisfaction, role manageability, role clarity) explained a significant amount of variance in turnover intentions above and beyond the absolute level of each respective measure. A key implication of the current study is that organizations seeking to improve their ability to assess risk for staff turnover may want to consider assessing staff at multiple points in time in order to identify systematic changes in key employee attitudes like turnover intentions and job satisfaction.
Nigerian Building Professionals’ Ethical Ideology and Perceived Ethical Judgement
Authors: Ameh John Oko , Odusami Koleola Tunwase
Published: October 2014

In recent years, Nigeria is often cited in the international media in connection with corruption and other unethical practices. The professionals in the Nigerian building industry are not immune from the national trend in ethical erosion. Moral philosophy or ethical ideology has been used to explain individuals’ reasoning about moral issues and consequent behaviour. This study examines building industry professionals’ ethical ideologies with a view to understanding their ethical behaviour in professional practice.  In carrying out this investigation, building professionals in clients’ organisations, contracting and consultancy organisations within the industry were asked to respond to the Ethics Position Questionnaire (EPQ) designed by Forsyth in order to determine their idealism and relativism level. Subsequently, they were classified into one of four groups, representing different ethical ideologies. The result indicates that the dominant ethical ideology of building industry professionals is situationism. The study predicts that the attitude of building industry professionals in practice, given the current socio-political and economic situation of Nigeria would possibly be unethical because of the extreme influence situational factors have on their behaviour. This finding is a bold step and necessary benchmark for resolving ethical issues within the industry and should be of interest to policy makers. It is also useful for intra professional ethical comparison.
Innovation, Procurement and Construction Industry Development
Authors: De Valence Geard
Published: October 2014

The implications for analysis of innovation in construction of theoretical developments in industrial organisation are considered in this research, as an attempt to outline a new approach to construction innovation incorporating the ideas found in knowledge based, technology centred models. The paper firstly summarises characteristics of the construction industry, focusing on their effects on innovation, before surveying some of the ideas about the sources of innovation and the expansion and application of knowledge. Construction can be seen as an industry with limited scope for knowledge externalities, where the procurement methods used by the industry’s clients do not pay for innovation. The following discussion uses recent developments in the research on the economics of innovation and industrial organization theory, such as research intensity and the endogenous sunk costs in competitive, fragmented, low research intensity industries. The effects on R&D of procurement methods and on industry structure are discussed, with a focus on the appropriability of innovations and the role of the client on the Heathrow Terminal 5 project. The paper concludes that the procurement methods used for building and construction projects appears to be a determining factor in the level of innovation in the construction industry
Drivers of Housing Demolition Decision Making and the Impact on Timber Waste Management
Authors: Forsythe Perry John
Published: October 2014

The study investigates housing demolition and timber waste recovery – with the aim to identify ways of improving recovery. Using case studies the research focused on demolisher decision making, their onsite processes and the associated network of participants that influence timber recovery. From the data, a process model was developed that identifies and orders the drivers of demolition decision making. One aspect of the model identified the initiators of demolition and the waste created, including issues revolving around the demolition feedstock. Another aspect covers organisational business drivers and includes site safety, productivity, economies of scale, market value of waste and supply chain entrepreneurship. A third component deals with project specific drivers including the recurring cost versus income equation that impacts on the viability of project level decisions. The model includes a typology of the operational onsite response to the above drivers. Here, the deconstruction approach was found to provide high timber recovery mainly used where high-value timber waste was involved; the miscellaneous salvage approach provided some recovery of high and low-value timber; the crunch and dump approach provided low recovery or dumping at landfill and was used where low and no-value timber was involved. An expected increase in supply of these latter timber categories creates a significant need to increase the market value of currently low value timber groups. Designing for deconstruction is also posed as a long term strategy for this.
A Principal Component Analysis of Project Management Construction Industry Competencies for the Ghanaian
Authors: Dobgegah Rockson , Owusu-Manu De-Graft , Omoteso Kamil
Published: October 2014

The study adopts a data reduction technique to examine the presence of any complex structure among a set of project management competency variables. A structured survey questionnaire was administered to 100 project managers to elicit relevant data, and this achieved a relatively high response rate of 54%. After satisfying all the necessary tests of reliability of the survey instrument, sample size adequacy and population matrix, the data was subjected to principal component analysis, resulting in the identification of six new thematic project management competency areas ; and were explained in terms of human resource management and project control; construction innovation and communication; project financial resources management; project risk and quality management; business ethics and; physical resources and procurement management. These knowledge areas now form the basis for lateral project management training requirements in the context of the Ghanaian construction industry. Key contribution of the paper is manifested in the use of the principal component analysis, which has rigorously provided understanding into the complex structure and the relationship between the various knowledge areas. The originality and value of the paper is embedded in the use of contextual-task conceptual knowledge to expound the six uncorrelated empirical utility of the project management competencies.
Construction Professionals Job Performance and Characteristics: A Comparison of Indigenous and Expatriate Construction Companies in Nigeria
Authors: Onukwube Henry Ndubuisi , Iyagba Reuben
Published: October 2014

AbstractJob performance is considered one of the most important constructs in human resources management because it helps to explain the value and utility that each employee adds to the organisation. The professionals in the Nigerian construction companies are not exception to the perceived low job performance rate within the industry. Extant literature points to the fact that job characteristics of employees can account for variance in their job performance rate.This study compares the job performance rate and job characteristics of construction professionals in indigenous and expatriate construction companies with a view to establish a relationship between job performance and job characteristics of construction professionals. A total of 762 questionnaires were collected and used for the study.  Eighty one (81) construction companies, 50 (62%) indigenous and 31 (38%) expatriate were selected using stratified random sampling technique. Data collected were analysed using mean item score, spearman rank correlation, linear regression analysis where appropriate. Findings of the study revealed that the relationship between job characteristics and job performance of construction professionals in construction companies in Nigeria is positive but low and the correlation coefficient is higher in expatriate construction companies. Based on the above finding, the study recommends that construction companies in Nigeria should endeavour and improve on their current core job dimensions (task significance, skill variety, task identity, autonomy and feedback) inherent in various jobs designed within their respective organizations as this will constitute as one of the variants that will improve the job performance rate of construction professionals.
Assessing knowledge retention in construction organisations: Cases from the UAE
Authors: Arif Mohammed , Khalfan Malik M A , Barnard James H , Heller Nathan A
Published: October 2014

Purpose: The purpose of this paper is to present different issues facing the problem of knowledge retention by construction sector companies in the UAE. Methodology: Existing framework in the area of knowledge retention has been used to assess three large construction consultancies in the UAE. The case study methodology used in this paper highlights some key issues in the area of knowledge retention in the UAE. Findings: Based on the analysis of the knowledge retention system the major drivers for its successful implementation are prevalence of a culture of sharing knowledge, reward and recognition for sharing knowledge, a technology platform that can accommodate multi formats of files, awareness of knowledge retention system and its benefits among its employees, and top management support. Research Limitations: The paper presents three case studies and draws conclusions about the UAE construction sector. Although the three companies are large companies, there are several Small and Medium sized Enterprise (SME) operating in the construction sector in the UAE. Future researchers need to look at these SMEs. Originality / Value: Through the three case studies, several issues related to the implementation of robust knowledge retention practices have been identified and highlighted for the UAE construction sector.
Establishing a common ground for the use of structural equation modelling for construction related research studies
Authors: Oke Ayodeji Emmanuel , Ogunsami Deji Rufus , Ogunlana Stephen
Published: October 2014

The use of structural equation modelling (SEM) for research studies in construction related field has been on the increase over the years. The essence of this study is not to compare the level of usage of SEM with other modelling methods, neither is it to examine its extent of adoption in construction management - as this has been researched in previous works - but to arrive at a common ground for future construction related research works, based on the findings and recommendations from existing studies on the subject of SEM. Research materials within and outside the field of construction management were reviewed and it was discovered that SEM using AMOS (covariance approach) is the most appropriate method for construction research studies. This is not just because it is the most available of the software programs, but because of the numerous benefits and advantages highlighted from previous studies. The study also recommended appropriate sample size as well as cut-off value for various required goodness-of-fit tests of SEM model.
BIM Handbook: A guide to Building Information Modeling for owners, managers, designers, engineers and contractors
Authors: Wang Xiangyu
Published: October 2014

2nd EditionC Eastman, P Teicholtz, R Sacks and K Liston ISBN: 978-0-470-54137-1 (Hardcover) 648 pages, 2011, AUD $105.00; NZD $120.00, USD 85.00, GBP57.50, EUR 68.00E-book version ISBN: 978-1-1180-2169-9 544 pages 2011 AUD $84.99 / NZD $99.99, USD69.99, GBP 47.99, EUR 54.99
A theory of construction management?
Authors: De Valence Gerard
Published: October 2014

The links between theory and construction management (CM), and for that matter construction economics (CE), are not strong (see de Valence 2011). This may be one of the reasons why they have not gained complete acceptance as academic disciplines and are not seen as distinct branches of economics and management respectively. Another reason may be that products and production (the focus of management and economic theories respectively) are not the same as projects and project management in general, and construction projects and CM in particular.
Textual complexity of standard conditions used in the construction industry
Authors: Rameezdeen Raufdeen , Rodrigo Anushi
Published: October 2014

Clearly written communication aids the understanding of construction contracts, resulting in less disputation. Past research, using opinion surveys rather than objective criteria, shows that construction contracts lack clarity and standard forms have become complex over time. The study outlined in this paper uses three objective measures of clarity developed by linguists to establish the readability of construction contracts. In addition, thirty industry professionals participated in a Cloze Test which measured the level of comprehension of clauses concerning disputes. The study verifies that contract conditions are very difficult to read, with college level reading skills needed to comprehend half of the clauses. However, the hypothesis that standard forms have become complex over time was not supported by the study. The study establishes a linear relationship between readability and comprehension, proving the hypothesis that improved readability increases the comprehension of a contract clause.
Performance measurement in the UK construction industry and its role in supporting the application of lean construction concepts
Authors: Sarhan Saad , Fox Andrew
Published: October 2014

Performance measurement has received substantial attention from researchers and the construction industry over the past two decades. This study sought to assess UK practitioners’ awareness of the importance of the use of appropriate performance measures and its role in supporting the application of Lean Construction (LC) concepts. To enable the study to achieve its objectives, a review of a range of measurements developed to evaluate project performance including those devoted to support LC efforts was conducted. Consequently a questionnaire survey was developed and sent to 198 professionals in the UK construction industry as well as a small sample of academics with an interest in LC. Results indicated that although practitioners recognise the importance of the selection of non-financial performance measures, it has not been properly and widely implemented. The study identified the most common techniques used by UK construction organisations for performance measurement, and ranked a number of non-financial key performance indicators as significant. Some professed to have embraced the Last Planner System methodology as a means for performance measurement and organisational learning, while further questioning suggested otherwise. It was also suggested that substance thinking amongst professionals could be a significant hidden barrier that militates against the successful implementation of LC.
Internationalisation of construction business and e-commerce: Innovation, integration and dynamic capabilities
Authors: Gajendran Thayaparan , Brewer Graham , Marimuthu Malliga
Published: October 2014

Despite the role of internet and web based applications in delivering competitive advantage through e-business process is widely acknowledged, little is done by way of research to use the dynamic capability framework, in exploring the role of ecommerce in the construction business internationalisation. The aim of this paper is to present a literature based theoretical exploration using dynamic capability view to discuss internationalising construction businesses through electronic commerce (e-commerce) platforms. This paper contextualises the opportunities for internationalising construction, using a mix of supply chain paradigms, embedded with e-commerce platforms. The paper concludes by identifying the potential of dynamic capabilities of a firm, exploiting the innovation and integration potential of different e-business systems, in contributing to the internationalisation of construction businesses. It proposes that contracting firms with developed dynamic capabilities, has the potential to exploit e-commerce platforms to channel upstream activities to an international destination, and also offers the firm’s products/services to international markets.
ICT & innovation: a case of integration in a regional construction firm
Authors: Brewer Graham , Gajendran Thayaparan , Runeson Goran
Published: October 2014

Construction firms in regional areas face considerable challenges to their competitiveness. Logistics, availability of suitable personnel, unfamiliarity with trading partners, and the tyranny of distance conspire to obstruct profitable engagement beyond their local area. Electronic information and communication technology (ICT) such as web-based project management applications and other forms of collaborative data sharing have the potential to mitigate many of these obstacles, but have yet to gain widespread acceptance, particularly by smaller regional firms who question their cost effectiveness. The attitudes of decision-makers and the impact of their decisions on intra- and inter-firm culture lie at the heart of ICT-mediated innovation. This paper presents a case study of a specialist subcontractor located in regional New South Wales and its involvement in a New Zealand project, whose competitiveness arose from using ICT to integrate its own supply chain. It also provided additional value by triggering collaboration and integration in the broader project team. The case reveals that these outcomes were symptomatic of the organisational culture of the subcontractor, and were achieved through a combination of leadership, collaboration, flexibility and pragmatism, redolent of dynamic capabilities.
A comparative approach to determining the growth of productivity of the New Zealand construction industry
Authors: Abbott Malcolm , Carson Chris
Published: October 2014

In recent years there has been increasing interest in the productivity and efficiency of the construction industry in New Zealand.  In part this interest has manifested itself in the increased use of numerous statistical techniques to determine the productivity and efficiency of the industry.  These efforts have, however, some degree of controversy.  The purpose of this paper is, therefore, threefold.  First it summarises the key structural findings that have been determined from past research into the construction industry in New Zealand.  Secondly it makes some comparisons between the construction industry’s productivity in New Zealand with that of the six states of Australia.  Finally it also considers potential areas for potential future research.
Managing geotechnical risk on US design-build transport projects
Authors: McLain Kevin , Gransberg Douglas D. , Loulakis Micheal C.
Published: October 2014

Awarding design-build (DB) contracts before a complete subsurface investigation is completed, makes mitigating the risk of differing site conditions difficult, if not impossible. The purpose of the study was to identify effective practices for managing geotechnical risk in DB projects, and it reports the results of a survey that included responses from 42 of 50 US state departments of transportation and a content analysis of DB requests for proposals from 26 states to gauge the client’s perspective, as well as 11 structured interviews with DB contractors to obtain the perspective from the other side of the DB contract.  A suite of DB geotechnical risk manage tools is presented based on the results of the analysis. Effective practices were found in three areas: enhancing communications on geotechnical issues before final proposals are submitted; the use of project-specific differing site conditions clauses; and expediting geotechnical design reviews after award. The major finding is that contract verbiage alone is not sufficient to transfer the risk of changed site conditions. The agency must actively communicate all the geotechnical information on hand at the time of the DB procurement and develop a contract strategy that reduces/retires the risk of geotechnical uncertainty as expeditiously as possible after award.
Modifications to standard forms of contract: the impact on readability
Authors: Rameezdeen Raufdeen , Rodrigo Anushi
Published: October 2014

Lack of clarity in contract documents can lead to disputes between contracting parties. Standard form contracts have evolved due to construction business becoming increasingly complex and the difficulty in drafting bespoke conditions of contract for each project. Numerous advantages have been identified in using standard forms of contract. However, clients often modify some clauses in order to include specific requirements for a project. While the consequences of ill-modifications to standard forms have been researched, no study has been done on the impact of these modifications on the clarity and readability of the document. Using 281 modified clauses from large infrastructure projects implemented in Sri Lanka, this study found that on balance modifications generally make the document more difficult to read; 60% of the sample clauses were more difficult to read compared to 40% becoming easier. More than 50% of the original and modified clauses were still at the ‘very difficult’ level of readability, which requires the equivalent of post-graduate level to understand. The study contends that modifications have not resulted in improved readability. The study highlights the necessity of clear and plain language when modifying contract documents.
A book review of “Best Practice in Construction Disputes – Avoidance, Management and Resolution”
Authors: Chan Philip
Published: October 2014

A book review of “Best Practice in Construction Disputes – Avoidance, Management and Resolution”.
Outdoor Workers and Sun Protection: Knowledge and Behaviour
Authors: Cioffi Jane , Wilkes Lesley , O'Brien Jess
Published: October 2014

Outdoor workers are at high risk of developing skin cancer. Primary prevention can potentiallyreduce the incidence of skin cancer in this group. This study aimed to determine theknowledge and sun protective behaviour of outdoor workers towards skin cancer. A shortquestionnaire was used to collect data from workers on construction sites during workinghours. Despite workers having knowledge of the risks of skin cancer their use of sun protectionwas less than satisfactory, particularly considering their cumulative exposure.Workplace health education programs for outdoor workers addressing sun protection areindicated, as is further research to increase understanding of issues workers have withsun protection in the workplace.
The Impact of Culture on International Management: A Survey of Project Communications in Singapore
Authors: Tran Dun , Skitmore Martin
Published: October 2014

This paper provides the results of an exploratory survey of construction industry managersin Singapore to isolate some of the common effects of national and organisational culture,together with the personal characteristics of managers, on the efficacy of project communication.By examination of significant correlation coefficients, the various types of influencesare identified. The results of the research suggest that the managers’ attitude andbehaviours toward communication may be guided to large extent by their level of competence.The study also provides evidence to suggest that the individuals’ understanding ofthe communication process and its barriers, the way they behave with other individualsand expect to be treated, varies according to national cultures.
Barriers to the Development of SME's in the Australian Construction Industry
Authors: Mills Anthony , Smith Jim , Love Peter
Published: October 2014

Small and medium sized companies (SMEs) operating in the construction industry in regionalareas of Australia often struggle to compete against city-based companies for constructionwork. This paper identifies the barriers that confront SMEs in areas outsidemajor cities, specifically in regional areas of Victoria (Australia) where local firms oftencompete unsuccessfully against large Melbourne-based organisations. The authors alsolook at the possibility of using e-commerce solutions to give regional SMEs greater competitivenessas well as considering possible policy initiatives that may assist these companiesto be more successful in tendering against city-based competition.
Building Energy and Cost Performance: An Analysis of Thirty Melbourne Case Studies
Authors: Langston Yu Lay , Langston Craig
Published: October 2014

This study investigates the energy and cost performance of thirty recent buildings in Melbourne, Australia. Commonly, building design decisions are based on issues pertaining to construction cost, and consideration of energy performance is made only within the context of the initial project budget. Even where energy is elevated to more importance, operating energy is seen as the focus and embodied energy is nearly always ignored. For the first time, a large sample of buildings has been assembled and analyzed to improve the understanding of both energy and cost performance over their full life cycle, which formed the basis of a wider doctoral study into the inherent relationship between energy and cost. The aim of this paper is to report on typical values for embodied energy, operating energy, capital cost and operating cost per square metre for a range of building functional types investigated in this research. The conclusion is that energy and cost have quite different profiles across projects, and yet the mean GJ/m2 or cost/m2 have relatively low coefficients of variation and therefore may be useful as benchmarks of typical building performance.
Allocating Risks in Public-Private Partnerships Using a Transaction Cost Economic Approach: A Case Study
Authors: Jin Xioa-Hua
Published: October 2014

Public-private partnership (PPP) projects are often characterisedby increased complexity and uncertainty due to their idiosyncrasyin the management and delivery processes such as long-termlifecycle, incomplete contracting, and the multitude of stakeholders.An appropriate risk allocation is particularly crucial to achievingproject success. This paper focuses on the risk allocation in PPPprojects and argues that the transaction cost economics (TCE)theory can integrate the economics part, which is currently missing,into the risk management research. A TCE-based approach isproposed as a logical framework for allocating risks between publicand private sectors in PPP projects. A case study of the SouthernCross Station redevelopment project in Australia is presented toillustrate the approach. The allocation of important risks is putunder scrutiny. Lessons learnt are discussed and alternativemanagement approaches drawing on TCE theory are proposed.
Technical Note: A new mechanism of 15 μm emission in the mesosphere-lower thermosphere (MLT)
Authors: Sharma R. D.
Published: October 2014

Abstract. Accurate knowledge of the rate as well as the mechanism of excitation of the bending mode of CO2 is necessary for reliable modeling of the mesosphere-lower thermosphere (MLT) region of the atmosphere. Assuming the excitation mechanism to be thermal collisions with atomic oxygen the rate coefficient derived from the observed 15 μm emission by space-based experiments differ from the laboratory measurements by a factor of 2–4. It is proposed that thermal collisions with N2, mediated by a near-resonant rotation to vibration energy transfer process, excite bending mode of CO2 by transferring energy from high rotational levels of thermal N2. Analogy with the excitation of the bending mode of CO2 by H2O, a process important in CO2 lasers, mediated by a near-resonant rotation-to vibration energy transfer process lends credibility to the hypothesis which has yet to be tested by direct calculations.
Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires
Authors: Jolleys M. D. , Coe H. , McFiggans G. , Taylor J. W. , O'Shea S. J. , Le Breton M. , Bauguitte S. J.-B. , Moller S. , Di Carlo P. , Aruffo E. , Palmer P. I. , Lee J. D.
Published: October 2014

Abstract. Airborne measurements of biomass burning organic aerosol (BBOA) from boreal forest fires reveal highly contrasting properties for plumes of different ages. These measurements, performed using an Aerodyne Research Inc. compact time-of-flight aerosol mass spectrometer (C-ToF-AMS) during the BORTAS (quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment in the summer of 2011, have been used to derive normalised excess organic aerosol (OA) mass concentrations (ΔOA/ΔCO), with higher average ratios observed closer to source (0.190 ± 0.010) than in the far-field (0.097 ± 0.002). The difference in ΔOA/ΔCO between fresh and aged plumes is influenced by a change in dominant combustion conditions throughout the campaign. Measurements at source sampled largely smouldering fires, while plumes encountered in the far-field originated from fires occurring earlier in the campaign when fire activity had been more intense. Changing combustion conditions also affect the vertical distribution of biomass burning emissions, as aged plumes from more flaming-dominated fires are injected to higher altitudes of up to 6000 m. Proportional contributions of the mass-to-charge ratio (m/z) 60 and 44 peaks in the AMS mass spectra to the total OA mass (denoted f60 and f44) are used as tracers for primary and oxidized BBOA, respectively. Given the shorter aging times associated with near-field plumes, f44 is lower on average than in more aged, transported plumes. However, high levels of ΔO3/ΔCO and -log(NOx/NOy) close to source indicate that emissions can be subject to very rapid oxidation over short timescales. Conversely, the lofting of plumes into the upper troposphere can lead to the retention of source profiles after transportation over extensive temporal and spatial scales, with f60 also higher on average in aged plumes. Evolution of OA composition with aging is comparable to observations of BB tracers in previous studies, revealing a consistent progression from f60 to f44. The elevated levels of oxygenation in aged plumes, and their association with lower average ΔOA/ΔCO, highlight the influence of OA losses during aging, although there remain considerable uncertainties regarding the role of combustion processes on BBOA production and composition.
Evidence for an unidentified ground-level source of formaldehyde in the Po Valley with potential implications for ozone production
Authors: Kaiser J. , Wolfe G. M. , Bohn B. , Broch S. , Fuchs H. , Ganzeveld L. N. , Gomm S. , Häseler R. , Hofzumahaus A. , Holland F. , Jäger J. , Li X. , Lohse I. , Lu K. , Rohrer F. , Wegener R. , Mentel T. F. , Kiendler-Scharr A. , Wahner A. , Keutsch F. N.
Published: October 2014

Abstract. Ozone concentrations in the Po Valley of Northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4±11%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po-Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.7 ppb h−1 (10%) before noon.
Chemical characterization of biogenic SOA generated from plant emissions under baseline and stressed conditions: inter- and intra-species variability for six coniferous species
Authors: Faiola C. L. , Wen M. , VanReken T. M.
Published: October 2014

Abstract. The largest global source of secondary organic aerosol in the atmosphere is derived from the oxidation of biogenic emissions. Plant stressors associated with a changing environment can alter both the quantity and composition of the compounds that are emitted. Alterations to the biogenic VOC profile could impact the characteristics of the SOA formed from those emissions. This study investigated the impacts of one global change stressor, increased herbivory, on the composition of SOA derived from real plant emissions. Herbivory was simulated via application of methyl jasmonate, a proxy compound. Experiments were repeated under pre- and post-treatment conditions for six different coniferous plant types. VOCs emitted from the plants were oxidized to form SOA via dark ozone-initiated chemistry. The SOA particle size distribution and chemical composition were measured using a scanning mobility particle sizer (SMPS) and Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-AMS), respectively. The aerosol mass spectra of pre-treatment biogenic SOA from all plant types tended to be similar with correlations usually greater than or equal to 0.90. The presence of a stressor produced characteristic differences in the SOA mass spectra. Specifically, the following m/z were identified as a possible biogenic stress AMS marker with the corresponding HR ion(s) shown in parentheses: m/z 31 (CH3O+), m/z 58 (C2H2O2+, C3H6O+) m/z 29 (C2H5+), m/z 57 (C3H5O+), m/z 59 (C2H3O2+, C3H7O+), m/z 71 (C3H3O2+, C4H7O+), and m/z 83 (C5H7O+). The first aerosol mass spectrum of SOA generated from the oxidation of the plant stress hormone, methyl jasmonate, is also presented. Elemental analysis results demonstrated an O:C range of baseline biogenic SOA between 0.3–0.47. The O:C of standard methyl jasmonate SOA was 0.52. Results presented here could be used to help identify a biogenic plant stress marker in ambient datasets collected in forest environments.
Simultaneous retrieval of effective refractive index and density from size distribution and light-scattering data: weakly absorbing aerosol
Authors: Kassianov E. , Barnard J. , Pekour M. , Berg L. K. , Shilling J. , Flynn C. , Mei F. , Jefferson A.
Published: October 2014

Abstract. We propose here a novel approach for retrieving in parallel the effective density and real refractive index of weakly absorbing aerosol from optical and size distribution measurements. Here we define "weakly absorbing" as aerosol single-scattering albedos that exceed 0.95 at 0.5 μm. The required optical measurements are the scattering coefficient and the hemispheric backscatter fraction, obtained in this work from an integrating nephelometer. The required size spectra come from mobility and aerodynamic particle size spectrometers commonly referred to as a scanning mobility particle sizer and an aerodynamic particle sizer. The performance of this approach is first evaluated using a sensitivity study with synthetically generated but measurement-related inputs. The sensitivity study reveals that the proposed approach is robust to random noise; additionally the uncertainties of the retrieval are almost linearly proportional to the measurement errors, and these uncertainties are smaller for the real refractive index than for the effective density. Next, actual measurements are used to evaluate our approach. These measurements include the optical, microphysical, and chemical properties of weakly absorbing aerosol which are representative of a variety of coastal summertime conditions observed during the Two-Column Aerosol Project (TCAP; http://campaign.arm.gov/tcap/). The evaluation includes calculating the root mean square error (RMSE) between the aerosol characteristics retrieved by our approach, and the same quantities calculated using the conventional volume mixing rule for chemical constituents. For dry conditions (defined in this work as relative humidity less than 55%) and sub-micron particles, a very good (RMSE ~ 3%) and reasonable (RMSE ~ 28%) agreement is obtained for the retrieved real refractive index (1.49 ± 0.02) and effective density (1.68 ± 0.21), respectively. Our approach permits discrimination between the retrieved aerosol characteristics of sub-micron and sub-10-micron particles. The evaluation results also reveal that the retrieved density and refractive index tend to decrease with an increase of the relative humidity.
Declining ozone exposure of European vegetation under climate change and reduced precursor emissions
Authors: Klingberg J. , Engardt M. , Karlsson P. E. , Langner J. , Pleijel H.
Published: October 2014

Abstract. The impacts of changes in ozone precursor emissions as well as climate change on the future ozone exposure of the vegetation in Europe were investigated. The ozone exposure is expressed as AOT40 (Accumulated exposure Over a Threshold of 40 ppb O3) as well as PODY (Phytotoxic Ozone Dose above a threshold Y). A new method is suggested to express how the length of the period during the year when coniferous and evergreen trees are sensitive to ozone might be affected by climate change. Ozone precursor emission changes from the RCP4.5 scenario were combined with climate simulations based on the IPCC SRES A1B scenario and used as input to the Eulerian Chemistry Transport Model MATCH from which projections of ozone concentrations were derived. The ozone exposure of vegetation over Europe expressed as AOT40 was projected to be substantially reduced between the periods 1990–2009 and 2040–2059 to levels which are well below critical levels used for vegetation in the EU directive 2008/50/EC as well as for crops and forests used in the LRTAP convention, despite that the future climate resulted in prolonged yearly ozone sensitive periods. The reduction in AOT40 was mainly driven by the emission reductions, not changes in the climate. For the toxicologically more relevant POD1 index the projected reductions were smaller, but still significant. The values for POD1 for the time period 2040–2059 were not projected to decrease to levels which are below critical levels for forest trees, represented by Norway spruce. This study shows that substantial reductions of ozone precursor emissions have the potential to strongly reduce the future risk for ozone effects on the European vegetation, even if concurrent climate change promotes ozone formation.
Mechanisms of microbial carbon sequestration in the ocean – future research directions
Authors: Jiao N. , Robinson C. , Azam F. , Thomas H. , Baltar F. , Dang H. , Hardman-Mountford N. J. , Johnson M. , Kirchman D. L. , Koch B. P. , Legendre L. , Li C. , Liu J. , Luo T. , Luo Y.-W. , Mitra A. , Romanou A. , Tang K. , Wang X. , Zhang C. , Zhang R.
Published: October 2014

Abstract. This paper reviews progress on understanding biological carbon sequestration in the ocean with special reference to the microbial formation and transformation of recalcitrant dissolved organic carbon (RDOC), the microbial carbon pump (MCP). We propose that RDOC is a concept with a wide continuum of recalcitrance. Most RDOC compounds maintain their levels of recalcitrance only in a specific environmental context (RDOCt). The ocean RDOC pool also contains compounds that may be inaccessible to microbes due to their extremely low concentration (RDOCc). This differentiation allows us to appreciate the linkage between microbial source and RDOC composition on a range of temporal and spatial scales. Analyses of biomarkers and isotopic records show intensive MCP processes in the Proterozoic oceans when the MCP could have played a significant role in regulating climate. Understanding the dynamics of the MCP in conjunction with the better constrained biological pump (BP) over geological timescales could help to predict future climate trends. Integration of the MCP and the BP will require new research approaches and opportunities. Major goals include understanding the interactions between particulate organic carbon (POC) and RDOC that contribute to sequestration efficiency, and the concurrent determination of the chemical composition of organic carbon, microbial community composition and enzymatic activity. Molecular biomarkers and isotopic tracers should be employed to link water column processes to sediment records, as well as to link present-day observations to paleo-evolution. Ecosystem models need to be developed based on empirical relationships derived from bioassay experiments and field investigations in order to predict the dynamics of carbon cycling along the stability continuum of POC and RDOC under potential global change scenarios. We propose that inorganic nutrient input to coastal waters may reduce the capacity for carbon sequestration as RDOC. The nutrient regime enabling maximum carbon storage from combined POC flux and RDOC formation should therefore be sought.