bluuebunny/crossref_metadata_2025 huggingface dataset:
Why and how to use virtual reality to study human social interaction: The challenges of exploring a new research landscape
Authors: Pan Xueni , Hamilton Antonia F. de C.
Published: March 2018

As virtual reality (VR) technology and systems become more commercially available and accessible, more and more psychologists are starting to integrate VR as part of their methods. This approach offers major advantages in experimental control, reproducibility, and ecological validity, but also has limitations and hidden pitfalls which may distract the novice user. This study aimed to guide the psychologist into the novel world of VR, reviewing available instrumentation and mapping the landscape of possible systems. We use examples of state‐of‐the‐art research to describe challenges which research is now solving, including embodiment, uncanny valley, simulation sickness, presence, ethics, and experimental design. Finally, we propose that the biggest challenge for the field would be to build a fully interactive virtual human who can pass a VR Turing test – and that this could only be achieved if psychologists, VR technologists, and AI researchers work together.
Generation of novel neuroinvasive prions following intravenous challenge
Authors: Aguilar‐Calvo Patricia , Bett Cyrus , Sevillano Alejandro M. , Kurt Timothy D. , Lawrence Jessica , Soldau Katrin , Hammarström Per , Nilsson K. Peter R. , Sigurdson Christina J.
Published: March 2018

Prions typically spread into the central nervous system (CNS), likely via peripheral nerves. Yet prion conformers differ in their capacity to penetrate the CNS; certain fibrillar prions replicate persistently in lymphoid tissues with no CNS entry, leading to chronic silent carriers. Subclinical carriers of variant Creutzfeldt–Jakob (vCJD) prions in the United Kingdom have been estimated at 1:2000, and vCJD prions have been transmitted through blood transfusion, however, the circulating prion conformers that neuroinvade remain unclear. Here we investigate how prion conformation impacts brain entry of transfused prions by challenging mice intravenously to subfibrillar and fibrillar strains. We show that most strains infiltrated the brain and caused terminal disease, however, the fibrillar prions showed reduced CNS entry in a strain‐dependent manner. Strikingly, the highly fibrillar mCWD prion strain replicated in the spleen and emerged in the brain as a novel strain, indicating that a new neuroinvasive prion had been generated from a previously non‐neuroinvasive strain. The new strain showed altered plaque morphology, brain regions targeted and biochemical properties and these properties were maintained upon intracerebral passage. Intracerebral passage of prion‐infected spleen re‐created the new strain. Splenic prions resembled the new strain biochemically and intracerebral passage of prion‐infected spleen re‐created the new strain, collectively suggesting splenic prion replication as a potential source. Taken together, these results indicate that intravenous exposure to prion‐contaminated blood or blood products may generate novel neuroinvasive prion conformers and disease phenotypes, potentially arising from prion replication in non‐neural tissues or from conformer selection.
The changing role of ornamental horticulture in alien plant invasions
Authors: van Kleunen Mark , Essl Franz , Pergl Jan , Brundu Giuseppe , Carboni Marta , Dullinger Stefan , Early Regan , González‐Moreno Pablo , Groom Quentin J. , Hulme Philip E. , Kueffer Christoph , Kühn Ingolf , Máguas Cristina , Maurel Noëlie , Novoa Ana , Parepa Madalin , Pyšek Petr , Seebens Hanno , Tanner Rob , Touza Julia , Verbrugge Laura , Weber Ewald , Dawson Wayne , Kreft Holger , Weigelt Patrick , Winter Marten , Klonner Günther , Talluto Lauren , Dehnen‐Schmutz Katharina
Published: March 2018

The number of alien plants escaping from cultivation into native ecosystems is increasing steadily. We provide an overview of the historical, contemporary and potential future roles of ornamental horticulture in plant invasions. We show that currently at least 75% and 93% of the global naturalised alien flora is grown in domestic and botanical gardens, respectively. Species grown in gardens also have a larger naturalised range than those that are not. After the Middle Ages, particularly in the 18th and 19th centuries, a global trade network in plants emerged. Since then, cultivated alien species also started to appear in the wild more frequently than non‐cultivated aliens globally, particularly during the 19th century. Horticulture still plays a prominent role in current plant introduction, and the monetary value of live‐plant imports in different parts of the world is steadily increasing. Historically, botanical gardens – an important component of horticulture – played a major role in displaying, cultivating and distributing new plant discoveries. While the role of botanical gardens in the horticultural supply chain has declined, they are still a significant link, with one‐third of institutions involved in retail‐plant sales and horticultural research. However, botanical gardens have also become more dependent on commercial nurseries as plant sources, particularly in North America. Plants selected for ornamental purposes are not a random selection of the global flora, and some of the plant characteristics promoted through horticulture, such as fast growth, also promote invasion. Efforts to breed non‐invasive plant cultivars are still rare. Socio‐economical, technological, and environmental changes will lead to novel patterns of plant introductions and invasion opportunities for the species that are already cultivated. We describe the role that horticulture could play in mediating these changes. We identify current research challenges, and call for more research efforts on the past and current role of horticulture in plant invasions. This is required to develop science‐based regulatory frameworks to prevent further plant invasions.
Federal policy ideas and involvement in Canadian urban transit, 2002‐2017
Authors: Towns William , Henstra Daniel
Published: March 2018

Although provincial and local governments bear primary responsibility for urban transit projects and operations in Canada, the Government of Canada engages intermittently in this policy field, mainly through research and short‐term funding programs. This article analyzes federal policy concerning urban transit over the period 2002‐2017, with a substantive focus on policy ideas—the cognitive and normative concepts that provide direction for, and shape the perceived legitimacy of, policy choices. Through a thematic content analysis of policy documents, this article explicates the paradigms, programmatic foci, frames and public sentiments that have underpinned federal urban transit policy over this 15‐year period.
The impact and role of officers of Parliament: Canada's conflict of interest and ethics commissioner
Authors: Bergman Gwyneth , Macfarlane Emmett
Published: March 2018

Officers of Parliament play a vital role in providing parliamentarians with access to critical information and resources that allow them to hold the government of the day to account. Critics have argued officers have exceeded their mandates and even threaten to supplant the opposition. Canada's Conflict of Interest and Ethics Commissioner (CIEC) holds a unique mandate, given that her primary focus concerns the behaviour of public office holders. This article draws on a comprehensive examination of the commissioner's reports and recommendations, and a content analysis of committee appearances to analyze and understand the impact and role of the CIEC. In contrast to the portrayal of other officers in the extant literature, we find that the office of the CIEC is constrained in its mandate and its impact limited by the nature and extent of its relationship with Parliament.
Open data and its institutional ecosystems: A comparative cross‐jurisdictional analysis of open data platforms
Authors: Kassen Maxat
Published: March 2018

This research note explores consistent patterns in the development of open data phenomena in various institutional contexts. The research is based on cross‐jurisdictional analysis of open data platforms promoted today in more than 30 countries at local, sub‐national, national and supranational levels. Key findings suggest that, institutionally, the instrumentation of the concept is a highly context‐dependable undertaking. Almost all observed cases tend to be affected by fundamental administrative frameworks within which they are promoted, which could generally be classified in accordance with three consistently repetitive institutional patterns. The research note offers a new research agenda to elaborate further on open data as institutional phenomena.
New Public Governance in health care: Health Technology Assessment for Canadian pharmaceuticals
Authors: Fierlbeck Katherine , Gardner William , Levy Adrian
Published: March 2018

The New Public Governance (NPG) paradigm addresses problems of complex and fragmented policy‐making. Health care is an increasingly complex policy area, and Canada has one of the most fragmented health care systems in the world. The theoretical articulation of NPG is compelling, and seems well suited to Canadian health care. However, it is not clear how these concepts could be applied to health care. We use the case of Health Technology Assessment (HTA) to evaluate the opportunities and limitations of NPG within a specific health care context. We argue that the kind of governance recommended by NPG has contributed to the development and integration of HTA in Canada. However, we note that this kind of governance structure may be limited to certain instances, and we describe the conditions under which horizontal governance structures in HTA were able to flourish.
Changes in glycaemic control, blood pressure and lipids 5 years following laparoscopic adjustable gastric banding combined with medical care in patients with type 2 diabetes: a longitudinal analysis
Authors: Mistry P. , Currie V. , Super P. , le Roux C. W. , Tahrani A. A. , Singhal R.
Published: March 2018

The long‐term outcomes of weight loss maintenance induced by laparoscopic adjustable gastric band (LAGB) followed by multidisciplinary medical care in patients with type 2 diabetes mellitus (T2DM) (beyond 3 years) are scarcely reported. Study aims were to determine the longer term metabolic outcomes following LAGB combined with medical care in patients with T2DM. This is a longitudinal analysis of 200 adults with T2DM who had LAGB between 2003 and 2008 and were followed up till 2013 at a single bariatric unit in a tertiary UK centre. A total of 200 patients (age 47 ± 9.7 years; body mass index [BMI] 52.8 ± 9.2 kg m−2; glycosylated haemoglobin (HbA1c) 7.9 ± 1.9% [62.8 mmol mol−1]; women, n = 123 [61.5%]; insulin treatment, n = 71 [35.5%]) were included. The mean follow‐up was 62.0 ± 13.0 months (range 18–84 months). There were significant reductions in body weight (−24.4 ± 12.3% [38 ± 22.7 kg]), HbA1c (−1.4 ± 2.0%), systolic blood pressure [BP] (−11.7 ± 23.5 mmHg), total cholesterol and triglyceride levels. The proportion of patients requiring insulin reduced from 36.2% to 12.3%. The overall band complication rate was 21% (21 patients). LAGB when combined with multidisciplinary medical care significantly improved metabolic outcomes in patients with T2DM independent of diabetes duration, and baseline BMI over 5 years. Diabetes duration and baseline BMI did not predict changes in glycaemic control, BP or lipids following LAGB.
A hybrid FAM‐CART model for online data classification
Authors: Seera Manjeevan , Lim Chee Peng , Tan Shing Chiang
Published: March 2018

In this paper, an online soft computing model based on an integration between the fuzzy ARTMAP (FAM) neural network and the classification and regression tree (CART) for undertaking data classification problems is presented. Online FAM network is useful for conducting incremental learning with data samples, whereas the CART model prevails in depicting the knowledge learned explicitly in a tree structure. Capitalizing on their respective advantages, the hybrid FAM‐CART model is capable of learning incrementally while explaining its predictions with knowledge elicited from data samples. To evaluate the usefulness of FAM‐CART, 2 sets of benchmark experiments with a total of 12 problems are used in both offline and online learning modes. The results are examined and compared with those published in the literature. The experimental outcome positively indicates that the online FAM‐CART model is useful for tackling data classification tasks. In addition, a decision tree is produced to allow users in understanding the predictions, which is an important property of the hybrid FAM‐CART model in supporting decision‐making tasks.
Replicative stress and alterations in cell cycle checkpoint controls following acetaminophen hepatotoxicity restrict liver regeneration
Authors: Viswanathan Preeti , Sharma Yogeshwar , Gupta Priya , Gupta Sanjeev
Published: March 2018

Objectives

Acetaminophen hepatotoxicity is a leading cause of hepatic failure with impairments in liver regeneration producing significant mortality. Multiple intracellular events, including oxidative stress, mitochondrial damage, inflammation, etc., signify acetaminophen toxicity, although how these may alter cell cycle controls has been unknown and was studied for its significance in liver regeneration.

Materials and methods

Assays were performed in HuH‐7 human hepatocellular carcinoma cells, primary human hepatocytes and tissue samples from people with acetaminophen‐induced acute liver failure. Cellular oxidative stress, DNA damage and cell proliferation events were investigated by mitochondrial membrane potential assays, flow cytometry, fluorescence staining, comet assays and spotted arrays for protein expression after acetaminophen exposures.

Results

In experimental groups with acetaminophen toxicity, impaired mitochondrial viability and substantial DNA damage were observed with rapid loss of cells in S and G2/M and cell cycle restrictions or even exit in the remainder. This resulted from altered expression of the DNA damage regulator, ATM and downstream transducers, which imposed G1/S checkpoint arrest, delayed entry into S and restricted G2 transit. Tissues from people with acute liver failure confirmed hepatic DNA damage and cell cycle‐related lesions, including restrictions of hepatocytes in aneuploid states. Remarkably, treatment of cells with a cytoprotective cytokine reversed acetaminophen‐induced restrictions to restore cycling.

Conclusions

Cell cycle lesions following mitochondrial and DNA damage led to failure of hepatic regeneration in acetaminophen toxicity but their reversibility offers molecular targets for treating acute liver failure.
Perceptions of risk characteristics of earthquakes compared to other hazards and their impact on risk tolerance
Authors: Henrich Liv , McClure John , Doyle Emma E.H.
Published: March 2018

People tolerate different levels of risk owing to a variety of hazards. Previous research shows that the psychometric properties of hazards predict people's tolerance of them. However, this work has not taken into account events such as earthquakes. The present study tested how earthquakes score vis‐à‐vis risk properties and risk tolerance as compared to five other familiar hazards. Participants from Wellington, New Zealand (N=139) rated these six hazards using measures of risk characteristics and risk tolerance. Participants demonstrated different levels of risk tolerance for the different hazards and viewed earthquakes as having similar risk features to nuclear power. They also preferred different risk mitigation strategies for earthquakes (more government funding) to the other five hazards (stronger legislation). In addition, earthquake risk tolerance was predicted by different risk characteristics than the other five hazards. These findings will help risk communicators in identifying which risk characteristics to target to influence citizens' risk tolerance.
Prospective study evaluating the use of nasal glucagon for the treatment of moderate to severe hypoglycaemia in adults with type 1 diabetes in a real‐world setting
Authors: Seaquist Elizabeth R. , Dulude Hélène , Zhang Xiaotian M. , Rabasa‐Lhoret Remi , Tsoukas George M. , Conway James R. , Weisnagel Stanley J. , Gerety Gregg , Woo Vincent C. , Zhang Shuyu , Carballo Dolorès , Pradhan Sheetal , Piché Claude A. , Guzman Cristina B.
Published: March 2018

In the present multicentre, open‐label, prospective, phase III study, we evaluated the real‐world effectiveness and ease of use of nasal glucagon (NG) in the treatment of moderate/severe hypoglycaemic events (HEs) in adults with type 1 diabetes (T1D). Patients and caregivers were taught how to use NG (3 mg) to treat moderate/severe HEs, record the time taken to awaken or return to normal status, and measure blood glucose (BG) levels over time. Questionnaires were used to collect information about adverse events and ease of use of NG. In the efficacy analysis population, 69 patients experienced 157 HEs. In 95.7% patients, HEs resolved within 30 minutes of NG administration. In all the 12 severe HEs, patients awakened or returned to normal status within 15 minutes of NG administration without additional external medical help. Most caregivers reported that NG was easy to use. Most adverse events were local and of low to moderate severity. In this study, a single, 3‐mg dose of NG demonstrated real‐life effectiveness in treating moderate and severe HEs in adults with T1D. NG was well tolerated and easy to use.
Two‐ and four‐dimensional echocardiography with high‐definition flow imaging and spatiotemporal image correlation in the diagnosis of fetal isolated partial anomalous pulmonary venous connection
Authors: Sun Xue , Lei Wenjia , Wang Yu , Amber Siddiqui Faiza , Zhang Ying
Published: March 2018

Partial anomalous pulmonary venous connection (PAPVC) is a rare malformation. We describe a case of PAPVC, in which the left pulmonary veins coursed to the left innominate vein through a vertical vein and finally drained into the right superior vena cava; the right pulmonary veins were connected to the left atrium. Tracing the origin and destination of abnormal vessels presented at the three‐vessel and trachea view is useful for the diagnosis. Four‐dimensional echocardiography with high‐definition flow imaging and spatiotemporal image correlation facilitates the identification of the drainage of fetal pulmonary veins, which should be considered as a complementary modality in obstetric ultrasonic examination when cardiac abnormalities are suspected.
Utility of postural change in differentiating sludge from thrombus in the left atrial appendage: A case report
Authors: Usuku Hiroki , Yamamoto Eiichiro , Yoshimura Hiromi , Tsunoda Ryusuke , Nishigami Kazuhiro , Nakajima Masamichi , Suzuki Ryusuke , Tsujita Kenichi
Published: March 2018

We detected symptomatic atrial fibrillation in a 64‐year‐old man who had undergone mitral valvuloplasty. While performing transesophageal echocardiography (TEE) in the left lateral decubitus position, we detected an isoechoic mass lesion at the bottom of the left atrial appendage (LAA). After changing the patient's position from left to right, the mass lesion dropped down from the bottom of the LAA, spread out into the left atrium, and appeared as a spontaneous echocardiographic contrast with mobility. We therefore diagnosed the mass lesion as not a thrombus but sludge. Changing the patient's position during TEE is useful for distinguishing sludge from thrombi.
E/eʹ ratio and left atrial area are predictors of atrial fibrillation in patients with hypertrophic cardiomyopathy
Authors: Costabel Juan Pablo , Galve Enrique , Terricabras María , Ametrano Clara , Ronderos Ricardo , Baranchuk Adrian , Evangelista Arturo , Avegliano Gustavo
Published: March 2018

Introduction

Atrial fibrillation (AF) occurs in about 20%–25% of patients with hypertrophic cardiomyopathy and is associated with increased risk of cardioembolism and heart failure impacting on patients’ morbidity and mortality. The aim of this study was to identify echocardiographic predictors of AF in a cohort of patients with hypertrophic cardiomyopathy (HCM).

Methods

Patients were recruited from 2 centers: Buenos Aires Cardiovascular Institute and the Hospital Vall d'Hebron of Barcelona which were analyzed together. Retrospective study using electronic charts.

Results

A total of 321 patients with HCM and no documented history of AF were included. Median follow‐up was 3 years. Mean age was 54 ± 16 years. Obstructive HCM was present in 41% of the patients, and 94.2% had preserved systolic function. Thirty‐eight patients developed AF during the follow‐up period (11.8%). Univariate analysis showed that age, maximum myocardial thickness, atrial area, an E/eʹ ratio ≥ 17, and systolic pulmonary pressure estimated by echocardiography were associated with new‐onset AF. Multivariate analysis showed that E/eʹ ≥ 17 ratio {HR 3.27 ([1.10–9.27] P = .033)} and atrial area {HR 1.06 ([1.01–1.13] P = .037)} remained predictors of AF.

Conclusions

An E/eʹ ratio ≥ 17, as an expression of left ventricular filling pressures with impact on the left atrium, and left atrial area ≥28 cm2 are strong predictors of AF in patients with HCM.
The effects of woodland habitat and biogeography on blue tit Cyanistes caeruleus territory occupancy and productivity along a 220 km transect
Authors: Shutt Jack D. , Bolton Margaret , Cabello Irene Benedicto , Burgess Malcolm D. , Phillimore Albert B.
Published: March 2018

The nesting phenology and productivity of hole‐nesting woodland passerines, such as tit species (Paridae), has been the subject of many studies and played a central role in advancing our understanding of the causes and consequences of trophic mismatch. However, as most studies have been conducted in mature, oak‐rich (Quercus sp.) woodlands, it is unknown whether insights from such studies generalise to other habitats used by woodland generalist species. Here we applied spatial mixed models to data collected over three years (2014–2016) from 238 nestboxes across 40 sites – that vary in woodland habitat and elevation – along a 220 km transect in Scotland. We evaluate the importance of habitat, biogeography and food availability as predictors of mesoscale among‐site variation in blue tit Cyanistes caeruleus nestbox occupancy and two components of productivity (clutch size and fledging success). We found that habitat was not a significant predictor of occupancy or clutch size but that occupancy exhibited pronounced biogeographic trends, declining with increasing latitude and elevation. However, fledging success, defined as the proportion of a clutch that fledged, was positively correlated with site level availability of birch, oak and sycamore, and tree diversity. The lack of correspondence between the effects of habitat on fledging success versus occupancy and clutch size may indicate that blue tits do not accurately predict the future quality of their breeding sites when selecting territories and laying clutches. We found little evidence of spatial autocorrelation in occupancy or clutch size, whereas spatial autocorrelation in fledging success extends over multiple sites, albeit non‐significantly. Taken together, our findings suggest that the relationship between breeding decisions and breeding outcomes varies among habitats, and we urge caution when extrapolating inferences from one habitat to others.
Suggestions of Power: Searching for Efficacy in Indonesia's Hypnosis Boom
Authors: Long Nicholas J.
Published: March 2018

From relative obscurity in the 1990s, hypnotherapy has become a major industry in contemporary Indonesia. This article examines its tremendous surge in popularity, and the subsequent trajectories of its vernacularization. It shows the hypnosis boom to have been underpinned by the introduction of a distinctive “30% theory, 70% practice” seminar format, structured in such a way as to allow mass‐market consumers to experience themselves as hypnotically efficacious. With such efficacy proving unsustainable outside the seminar context, Indonesians reached for and developed alternative conceptions of “hypnosis” that allowed them to continue as effective hypnotherapists. Such material demonstrates the value of incorporating a theory of interactional affordances into anthropological models of cultural transmission and globalization. [efficacy, hypnosis, globalization, Indonesia, interaction, psychotherapy]
Elucidating the sponge stress response; lipids and fatty acids can facilitate survival under future climate scenarios
Authors: Bennett Holly , Bell James J. , Davy Simon K. , Webster Nicole S. , Francis David S.
Published: March 2018

Ocean warming (OW) and ocean acidification (OA) are threatening coral reef ecosystems, with a bleak future forecast for reef‐building corals, which are already experiencing global declines in abundance. In contrast, many coral reef sponge species are able to tolerate climate change conditions projected for 2100. To increase our understanding of the mechanisms underpinning this tolerance, we explored the lipid and fatty acid (FA) composition of four sponge species with differing sensitivities to climate change, experimentally exposed to OW and OA levels predicted for 2100, under two CO2 Representative Concentration Pathways. Sponges with greater concentrations of storage lipid, phospholipids, sterols and elevated concentrations of n‐3 and n‐6 long‐chain polyunsaturated FA (LC PUFA), were more resistant to OW. Such biochemical constituents likely contribute to the ability of these sponges to maintain membrane function and cell homeostasis in the face of environmental change. Our results suggest that n‐3 and n‐6 LC PUFA are important components of the sponge stress response potentially via chain elongation and the eicosanoid stress‐signalling pathways. The capacity for sponges to compositionally alter their membrane lipids in response to stress was also explored using a number of specific homeoviscous adaptation (HVA) indicators. This revealed a potential mechanism via which additional CO2 could facilitate the resistance of phototrophic sponges to thermal stress through an increased synthesis of membrane‐stabilizing sterols. Finally, OW induced an increase in FA unsaturation in phototrophic sponges but a decrease in heterotrophic species, providing support for a difference in the thermal response pathway between the sponge host and the associated photosymbionts. Here we have shown that sponge lipids and FA are likely to be an important component of the sponge stress response and may play a role in facilitating sponge survival under future climate conditions.
Arsenic Remediation Field Study Using a Sulfate Reduction and Zero‐Valent Iron PRB
Authors: Beaulieu Brett , Ramirez Rachel Elena
Published: March 2018

Toxic and carcinogenic effects of arsenic in drinking water continue to impact people throughout the world and arsenic remains common in groundwater at cleanup sites and in areas with natural sources. Advances in groundwater remediation are needed to attain the low concentrations that are protective of human health and the environment. In this article, we present the successful use of a permeable reactive barrier (PRB) utilizing sulfate reduction coupled with zero‐valent iron (ZVI) to remediate the leading edge of a dissolved arsenic plume in a wetland area near Tacoma, Washington. A commercially available product (EHC‐M®, Adventus Americas Inc., Freeport, Illinois) that contains ZVI, organic carbon substrate, and sulfate was injected into a reducing, low‐seepage‐velocity aquifer elevated in dissolved arsenic and iron from a nearby, slag‐containing landfill. Removal effectiveness was strongly correlated with sulfate concentration, and was coincident with temporary redox potential (Eh) reductions, consistent with arsenic removal by iron sulfide precipitation. The PRB demonstrates that induced sulfate reduction and ZVI are capable of attaining a regulatory limit of 5 µg/L total arsenic, capturing of 97% of the arsenic entering the PRB, and sustaining decreased arsenic concentrations for approximately 2 years, suggesting that the technology is appropriate for consideration at other sites with similar hydrogeochemical conditions. The results indicate the importance of delivery and longevity of minimum sulfate concentrations and of maintaining sufficient dissolved organic carbon and/or microscale ZVI to precipitate FeS, a precursor phase to arsenic‐bearing pyrite that may provide a stable, long‐term sink for arsenic.
Influence of Shallow Geology on Volatile Organic Chemical Attenuation from Groundwater to Deep Soil Gas
Authors: McHugh Thomas E. , Beckley Lila , Bailey Danielle
Published: March 2018

Vapor intrusion pathway evaluations commonly begin with a comparison of volatile organic chemical (VOC) concentrations in groundwater to generic, or Tier 1, screening levels. These screening levels are typically quite low reflecting both a desired level of conservatism in a generic risk screening process as well as limitations in understanding of physical and chemical processes that impact vapor migration in the subsurface. To study the latter issue, we have collected detailed soil gas and groundwater vertical concentration profiles and evaluated soil characteristics at seven different sites overlying chlorinated solvent contaminant plumes. The goal of the study was to evaluate soil characteristics and their impacts on VOC attenuation from groundwater to deep soil gas (i.e., soil gas in the unsaturated zone within 2 feet of the water table). The study results suggest that generic screening levels can be adjusted by a factor of 100× at sites with fine‐grained soils above the water table, as identified by visual observations or soil air permeability measurements. For these fine‐grained soil sites, the upward‐adjusted screening levels maintain a level of conservatism while potentially eliminating the need for vapor intrusion investigations at sites that may not meet generic screening criteria.
A Revised Conceptual Model to Reproduce the Distribution of Chlorinated Solvents in the Rho Aquifer (Italy)
Authors: Pedretti Daniele , Masetti Marco , Beretta Giovanni P. , Vitiello Mariangela
Published: March 2018

To make cost‐effective decisions regarding aquifer protection against chlorinated solvent contamination, a conceptual site model explaining the hydrodynamic behavior of these solvents needs to account for soil heterogeneities in sufficient detail. Among the key requirements, it is necessary to perform site‐specific characterization of (1) the architecture and type of chlorinated solvent sources, (2) the architecture, nature, and distribution of aquitards (bodies of low permeability), and (3) local groundwater dynamics. Local‐scale data are often lacking and regional descriptions are therefore adopted with the consequence of losing small‐scale features that control local chlorinated solvent migration which, in turn, limits the effectiveness of safeguard facilities. This article addresses these arguments, focusing on the Rho aquifer (Italy). We show that the local conceptual model must integrate small‐scale architectural and hydrodynamic anomalies of the aquifers and aquitards with regional trends and the sedimentary origin of the aquifers. New evidence was found by processing stratigraphic logs, piezometric heads and solute concentrations from local wells. The revised conceptual model should account for the occurrence of secondary chlorinated solvent sources located in depressions on the aquitard surface separating the two upper and most contaminated Rho aquifers. While the spatial distribution of depressions is in accordance with regional sedimentological dynamics, the direction of local groundwater flow at various levels within the main hydrogeological unit is remarkably opposite to the regional groundwater flow direction. These findings, along with evidence of vertical heterogeneous soil texture and stratification of chlorinated solvents in various phases, are supported by a simple particle‐tracking model and suggest how to redefine the conceptual model and, consequently, how to design safeguard facilities to effectively prevent further plume migration.
Removal of PCE DNAPL from Tight Clays Using In Situ Thermal Desorption
Authors: Heron Gorm , Lachance John , Baker Ralph
Published: March 2018

This paper presents a full‐scale thermal remediation of a brownfields site near San Francisco, California. In Situ Thermal Desorption (ISTD) was used for treatment of chlorinated solvents in a tight clay below the water table. The site had contaminants in concentrations indicating that a tetrachloroethene (PCE)‐rich DNAPL was present. A target volume of 5097 m3 of subsurface material to a depth of 6.2 m was treated for a period of 110 d of heating. Energy was delivered through 126 thermal conduction heater borings, and vapors were extracted from a combination of vertical and horizontal vacuum wells. Approximately 2540 kg of contaminants were recovered in the extracted vapors by the end of treatment. The PCE concentration in the clay was reduced from as high as 2700 mg/kg to an average concentration of 0.012 mg/kg within 110 d of heating (a reduction of >99.999%). Similar effectiveness was documented for TCE, cis‐1,2‐DCE, and vinyl chloride. A total of 2.2 million kWh of electric power was used to heat the site. Approximately 45% of this energy was used to heat the subsurface to the target temperature. Another 53% was necessary to boil approximately 41% of the groundwater within the treatment zone, creating approximately 600 pore volumes of steam by the end of the 110‐d heating and treatment period. Steam generation thus occurred within the clay. Partitioning of the contaminants into the steam and its removal comprised the dominant remedial mechanism. The steam migrated laterally toward the ISTD heaters, where it encountered a small dry region adjacent to each of the heaters, which served as a preferential pathway allowing the steam to migrate upward along the heaters to the more permeable vadose zone. There the steam was captured by a system of vertical and horizontal vacuum extraction wells. This vapor removal strategy facilitated effective thermal treatment of the tight clays located below the water table. Features of a robust design are extension of the heaters at least 1.2 m deeper than the treatment depth, and the installation of shallow horizontal vapor collection wells which allow for establishment of pneumatic control.
Phytoscreening: A Comparison of In Planta Portable GC‐MS and In Vitro Analyses
Authors: Limmer Matt A. , Martin Gregory D. , Watson Christopher J. , Martinez Camilo , Burken Joel G.
Published: March 2018

Phytoscreening has been proven to rapidly delineate subsurface contaminant plumes for semiquantitative site assessment, with minimal impact to property or ecology through the collection and analysis of tree cores. Here, three phytoscreening methods were applied concurrently to identify multiple chlorinated volatile organic compounds (cVOCs) in a phytoremediation treatment system at a contaminated industrial facility. Tree coring, in planta gas chromatography–mass spectrometry (GC‐MS), and in planta passive sampling showed general agreement, with the in planta GC‐MS providing the quickest but least quantitative results. The portable GC‐MS sampling and analysis method identified six cVOCs in the xylem of hybrid poplars (Populus sp.) in the phytoremediation plot. These real‐time data can permit onsite identification and delineation of the contaminants, allowing for adaptive sampling during a single mobilization to a site. The in vitro methods provided quantitative data across two sampling campaigns, as relative cVOC concentrations remained similar between the two trips, despite a decrease in absolute cVOC concentrations from August to October. Overall, this research demonstrates the advantages and limitations of three phytoscreening techniques.
Effects of a Dual‐Pump Crude‐Oil Recovery System, Bemidji, Minnesota, USA
Authors: Delin Geoffrey N. , Herkelrath William N.
Published: March 2018

A crude‐oil spill occurred in 1979 when a pipeline burst near Bemidji, MN. In 1998, the pipeline company installed a dual‐pump recovery system designed to remove crude oil remaining in the subsurface at the site. The remediation from 1999 to 2003 resulted in removal of about 115,000 L of crude oil, representing between 36% and 41% of the volume of oil (280,000 to 316,000 L) estimated to be present in 1998. Effects of the 1999 to 2003 remediation on the dissolved plume were evaluated using measurements of oil thicknesses in wells plus measurements of dissolved oxygen in groundwater. Although the recovery system decreased oil thicknesses in the immediate vicinity of the remediation wells, average oil thicknesses measured in wells were largely unaffected. Dissolved‐oxygen measurements indicate that a secondary plume was caused by disposal of the pumped water in an upgradient infiltration gallery; this plume expanded rapidly immediately following the start of the remediation in 1999. The result was expansion of the anoxic zone of groundwater upgradient and beneath the existing natural attenuation plume. Oil‐phase recovery at this site was shown to be challenging, and considerable volumes of mobile and entrapped oil remain in the subsurface despite remediation efforts.
Use of Chemical and Isotopic Signatures to Distinguish Between Uranium Mill‐Related and Naturally Occurring Groundwater Constituents
Authors: Kamp Susan D. , Morrison Stan J.
Published: March 2018

Chemical and isotopic signatures were determined in groundwater samples to aid in distinguishing the source of contamination in three desert arroyos and a buried channel (the swale) near Shiprock, New Mexico. The contamination in the swale and one of the arroyos, Many Devils Wash, was previously attributed to a former uranium mill site because of the similar suite of contaminants (nitrate, selenium, sulfate, and uranium) and the close (0.8 km) proximity. The other two arroyos are far removed from the mill site and could not have received contamination from it. Principal component and cluster analysis indicated similarities in groundwater chemistry among the swale and the three arroyos that contrasted with groundwater chemistry at the disposal cell. Disposal cell groundwater is characterized by high uranium and bicarbonate concentrations, whereas that in remaining study areas is characterized by high sodium and sulfate, but lower uranium concentrations. Mancos Shale forms the bedrock in the region and contains elevated concentrations of the same chemical constituents that appear in the swale and arroyo groundwater. Dissolved sulfate in arroyo groundwater was depleted in sulfur‐34, in contrast to mill‐derived sulfate with more enriched sulfur‐34. Uranium‐234 to uranium‐238 activity ratios (ARs) were near the secular equilibrium value of 1 in mill site groundwater, whereas ARs in all arroyo groundwater samples exceeded 2. Elevated tritium activities present in mill site groundwater (49 to 142 pCi/L) are attributed to the mill being operated during atomic bomb testing in the 1950s and 1960s. The combined chemical and isotopic results indicate that groundwater in Many Devils Wash and the swale was likely derived from the Mancos Shale and not from the milling operation.
Method for Assessing Source Zone Natural Depletion at Chlorinated Aliphatic Spill Sites
Authors: Ekre Ryan , Johnson Paul C. , Rittmann Bruce E. , Krajmalnik‐Brown Rosa
Published: March 2018

This work focuses on the site‐specific assessment of source zone natural attenuation (SZNA) at chlorinated aliphatic hydrocarbon (CAH)‐impacted sites. The approach is similar in some ways, but different in other ways from recently proposed SZNA assessment paradigms for petroleum‐impacted sites. The similarities lie in the organization of the approach around determining: (1) whether or not SZNA is occurring, (2) the current SZNA rate, and (3) what is the future projection for SZNA rate changes and the final state of the source zone. Differences lie in how those rates are determined, especially with respect to the quantities measured and data reduction. Petroleum‐impacted site SZNA approaches emphasize quantifying fluxes of electron acceptors, while the proposed CAH assessment approach emphasizes quantifying parent and daughter compound fluxes. A paradigm for assessing SZNA at CAH sites is presented and its use is illustrated, for example former dry cleaner site, where the SZNA rate was approximately 3.5 kg/year as tetrachloroethylene (PCE) with about 80% of the mass loss attributed to groundwater flow and 20% attributed to vapor transport.
Estimating the Impact of Vadose Zone Sources on Groundwater to Support Performance Assessment of Soil Vapor Extraction
Authors: Oostrom M. , Truex M.J. , Rice A.K. , Johnson C.D. , Carroll K.C. , Becker D.J. , Simon M.A.
Published: March 2018

Soil vapor extraction (SVE) is a prevalent remediation remedy for volatile organic compound (VOC) contaminants in the vadose zone. To support selection of an appropriate condition at which SVE may be terminated for site closure or for transition to another remedy, an evaluation is needed to determine whether vadose zone VOC contamination has been diminished sufficiently to keep groundwater concentrations below threshold values. A conceptual model for this evaluation was developed for VOC fate and transport from a vadose zone source to groundwater when vapor‐phase diffusive transport is the dominant transport process. A numerical analysis showed that, for these conditions, the groundwater concentration is controlled by a limited set of parameters, including site‐specific dimensions, vadose zone properties, and source characteristics. On the basis of these findings, a procedure was then developed for estimating groundwater concentrations using results from the three‐dimensional multiphase transport simulations for a matrix of parameter value combinations and covering a range of potential site conditions. Interpolation and scaling processes are applied to estimate groundwater concentrations at compliance (monitoring) wells for specific site conditions of interest using the data from the simulation results. The interpolation and scaling methodology using these simulation results provides a far less computationally intensive alternative to site‐specific three‐dimensional multiphase site modeling, while still allowing for parameter sensitivity and uncertainty analyses. With iterative application, the approach can be used to consider the effect of a diminishing vadose zone source over time on future groundwater concentrations. This novel approach and related simulation results have been incorporated into a user‐friendly Microsoft® Excel®‐based spreadsheet tool entitled SVEET (Soil Vapor Extraction Endstate Tool), which has been made available to the public.
Factors Controlling In Situ Biogeochemical Transformation of Trichloroethene: Column Study
Authors: Evans Patrick J. , Nguyen Dung , Chappell Rick W. , Whiting Kent , Gillette John , Bodour Adria , Wilson John T.
Published: March 2018

In situ biogeochemical transformation involves biological formation of reactive minerals in an aquifer that can destroy chlorinated solvents such as trichloroethene (TCE) without accumulation of intermediates such as vinyl chloride. There is uncertainty regarding the materials and geochemical conditions that are required to promote biogeochemical transformation. The objective of this study was to identify amendments and biogeochemical conditions that promote in situ biogeochemical transformation. Laboratory columns constructed with plant mulch were supplemented with different amendments and were operated under varying conditions of water chemistry and hydraulic residence time. Four patterns of TCE removal were observed: (1) no removal, (2) biotic transformation of TCE to cis‐1,2‐dichloroethene (cis‐1,2‐DCE), (3) biogeochemical transformation of TCE without accumulation of reductive dechlorination products, and (4) mixed behavior where a combination of patterns was observed either simultaneously or over time. Principal coordinates analysis and analysis of variance (ANOVA) identified factors that promoted biogeochemical transformation: (1) high influent sulfate concentration, (2) relatively high hydraulic retention time, (3) supplementation of mulch with vegetable oil, and (4) addition of hematite or magnetite. The combination of the first three factors promoted complete sulfate reduction and a high volumetric sulfate consumption rate. The fourth factor provided a source of ferrous iron and/or a surface to which sulfide could react to form reactive iron sulfides. Many columns demonstrated either no TCE removal or a biotic TCE transformation pattern. Modification of column operation to include all four factors identified above promoted biogeochemical transformation in these columns. These results support the importance of the factors in biogeochemical transformation.
Development and Testing of a Field Screening Method Based on Bubbling Extraction and Photoionization Detection for Measurement of Benzene and Total VOCs
Authors: Devine Catalina Espino , Bennett Peter , Synowiec Karen , Nelson Sheldon , Mohler Rachel , Einarson Murray
Published: March 2018

A field screening method was developed for rapid measurement of benzene and gasoline range total petroleum hydrocarbons (TPHg) concentrations in groundwater. The method is based on collecting photoionization detector (PID) measurements from vapor samples. The vapor samples are collected by bubbling air through groundwater samples (air sparging) with a constant volume, temperature and sparging rate. The level of accuracy, sensitivity, precision, and statistical significance of the estimated concentrations, derived from the screening method, are comparable to conventional laboratory analytical results at concentrations equal to or greater than 150 µg/L for benzene and greater than 50 µg/L for TPHg. The method's concentration estimations can assist in making real‐time decisions regarding location of dissolved plumes and light nonaqueous phase liquid (LNAPL) source zones at many fuel release sites. The screening method was tested in the laboratory and in the field with 208 and 107 samples, respectively. The study concludes that the screening method can be used as a tool to aid in completing a site conceptual model as well as analyzing groundwater from monitoring wells.
Assessment of Density‐Induced Tracer Movement in Groundwater Velocity Measurements with Point Velocity Probes (PVPs)
Authors: Schillig P.C. , Devlin J.F. , McElwee C.D. , Walter K. , Gibson B.
Published: March 2018

The concept of equivalent freshwater head was adapted to predict the conditions under which density‐driven flow would adversely impact measured groundwater velocities using point velocity probes (PVPs). Theoretically, vertical flow will result from any density contrast between the PVP tracer and the groundwater. However, laboratory testing of tracers with salinities ranging from 0 to 2000 mg NaCl/L showed that horizontal velocities could be determined with good accuracy with up to 60% of the total flow being vertical due to density effects in a gravel medium. The available data suggest that density effects are less likely to be pronounced in sandy sediments. The relative amount of vertical flow due to tracer density can be estimated from vertical and horizontal velocities measured with PVPs, or from the ratio of vertical to horizontal hydraulic gradients. The equivalent freshwater gradient produced from a given tracer salinity at 10 °C (a typical groundwater temperature at moderate latitudes) can be estimated from 7.80 × 10−7 × (MNaCl), where MNaCl is the mass of NaCl added, in mg, to 1 L of site groundwater in the mixing of the tracer. Equations for other temperatures were also determined.