Value and Outcome Uncertainty as Explanations for the WTA vs WTP Disparity: Theory and Experimental Evidence

This paper contributes to the widespread discussion of the sources of the divergence between WTA and WTP values. The paper reports on theoretical and empirical investigations which show that value and outcome uncertainty offer an explanation for this disparity. Given a set of hypotheses generated by the theory, the paper investigates the disparity using an inducedvalue experimental laboratory setting. The incentive-compatible Becker-DeGroot-Marshak mechanism is employed to elicit the WTP and WTA values. Two conclusions can be drawn from the empirical results. First, the WTA - WTP difference is generally increasing in both value and outcome uncertainty. Second, a re-contracting option reduces the disparity when it arises from value uncertainty. Key Words: Experimental, Uncertainty, WTP-WTA disparity

Report on water quality data evaluation and program design services for the James and York rivers in conjunction with the 208 planning program for the Tidewater region of Virginia

The study area considered in this report includes the following: The James River from Fort Monroe to the mouth of the Chickahominy River (statute mile 45) including the small tributaries on the north shore but not the Chickahominy; the York River from its mouth to the confluence of the Mattaponi and Pamunkey at West Point (statute mile 33.5) including the small tributaries along the south shore; and the small drainage area adjacent to Chesapeake Bay lying between the York and James basins. The two rivers included in this basin are Poquoson River and Back River

The Wide Field Spectrograph (WiFeS): Performance and Data Reduction

This paper describes the on-telescope performance of the Wide Field Spectrograph (WiFeS). The design characteristics of this instrument, at the Research School of Astronomy and Astrophysics (RSAA) of the Australian National University (ANU) and mounted on the ANU 2.3m telescope at the Siding Spring Observatory has been already described in an earlier paper (Dopita et al. 2007). Here we describe the throughput, resolution and stability of the instrument, and describe some minor issues which have been encountered. We also give a description of the data reduction pipeline, and show some preliminary results.Comment: Accepted for publication in Astrophysics & Space Science, 15pp, 11 figure

Active Layer Groundwater Flow: The Interrelated Effects of Stratigraphy, Thaw, and Topography

The external drivers and internal controls of groundwater flow in the thawed “active layer” above permafrost are poorly constrained because they are dynamic and spatially variable. Understanding these controls is critical because groundwater can supply solutes such as dissolved organic matter to surface water bodies. We calculated steady‐state three‐dimensional suprapermafrost groundwater flow through the active layer using measurements of aquifer geometry, saturated thickness, and hydraulic properties collected from two major landscape types over time within a first‐order Arctic watershed. The depth position and thickness of the saturated zone is the dominant control of groundwater flow variability between sites and during different times of year. The effect of water table depth on groundwater flow dwarfs the effect of thaw depth. In landscapes with low land‐surface slopes (2–4%), a combination of higher water tables and thicker, permeable peat deposits cause relatively constant groundwater flows between the early and late thawed seasons. Landscapes with larger land‐surface slopes (4–10%) have both deeper water tables and thinner peat deposits; here the commonly observed permeability decrease with depth is more pronounced than in flatter areas, and groundwater flows decrease significantly between early and late summer as the water table drops. Groundwater flows are also affected by microtopographic features that retain groundwater that could otherwise be released as the active layer deepens. The dominant sources of groundwater, and thus dissolved organic matter, are likely wet, flatter regions with thick organic layers. This finding informs fluid flow and solute transport dynamics for the present and future Arctic.Plain Language SummaryGroundwater flow in permafrost watersheds is potentially a key component of global carbon budgets because permafrost soil stores vast amounts of carbon that could be mobilized due to a warming climate and the corresponding increase in soil thaw. In addition to carrying carbon, groundwater can supply important nutrients and solutes to surface waters. However, we do not yet understand the factors that control groundwater flow in soils above permafrost because saturation changes rapidly and continuously, and soil hydraulic properties are largely unknown. We created measurement‐informed calculations of groundwater flow from areas of permafrost with different characteristics and found that soil types, which vary based on the slope of the land surface, are the most important control. Near‐surface soils were identical in hillslopes and valleys, whereas deeper soils in hillslopes allowed for less groundwater flow than in valleys. In early summer, when only the near‐surface soils were thawed, groundwater flows in the hillslopes and valley were similar. In late summer, when the deeper soil was thawed, groundwater flow in the valley remained high, but flow in the hillslope was negligible. Our observations also showed that small mounds on the land surface caused groundwater to be trapped behind underground ice dams.Key PointsDetailed measurements of hydraulic head, hydraulic conductivity, and saturated thicknesses in active layers were made over time and spaceThree main soil layers consistently comprise the stratigraphy of the active layer across the studied Arctic watershedGroundwater flow depends most on the depth of the water table and the subsurface stratigraphy, which varies based on landscape typePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151862/1/wrcr24085_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151862/2/wrcr24085.pd

Chronic Physical Health Conditions Among Homeless

ABSTRACT Objective: Morbidity and mortality among homeless individuals is higher than the general population. This study aims to determine the prevalence of current self-reported, chronic physical health conditions in a large sample of homeless people with sub-samples from shelters and street in British Columbia, Canada. Methods: Cross-sectional survey applying modified version of the ‘National Survey of Homeless Assistance Providers and Clients (NSHAPC)’ questionnaire in multiple sites in Vancouver, Victoria and Prince George, British Columbia, Canada. Sample: Five hundred homeless individuals were surveyed between May and September of 2009. A person was defined as homeless if he/she had a self-identified living status of being without permanent housing prior to study entry for a minimum duration of one month. The main outcome measures were prevalence rates of self-reported chronic physical health conditions. A chronic physical health condition was defined as a condition, expected to last or had already lasted 6 months or more, which had been diagnosed by a health professional. Results: The most commonly self-reported, chronic, physical health condition in this group of homeless participants was history of head injury with subsequent loss of consciousness, dizziness, confusion, or disorientation (63.6%) followed by back problems (38.8%), chronic hepatitis (34.6%), migraine headaches (29.2%), and arthritis (28.4%). Chronic obstructive lung disease was reported by 15.8% of the participants, and high blood pressure by 15.6%. 7.6% indicated they were HIV-positive and/or had AIDS. Conclusion: Homeless people have a high prevalence of chronic physical health condition, in the following areas: neurological, musculoskeletal, infectious and respiratory diseases. Precarious living conditions and housing, poor nutrition, psychosocial stress, smoking, and substance use are among common detrimental risk factors for many of these conditions. Keywords: chronic disease, homeless, HIV, Hepatitis C, back pain, physical healt

Active Layer Groundwater Flow: The Interrelated Effects of Stratigraphy, Thaw, and Topography

The external drivers and internal controls of groundwater flow in the thawed “active layer” above permafrost are poorly constrained because they are dynamic and spatially variable. Understanding these controls is critical because groundwater can supply solutes such as dissolved organic matter to surface water bodies. We calculated steady‐state three‐dimensional suprapermafrost groundwater flow through the active layer using measurements of aquifer geometry, saturated thickness, and hydraulic properties collected from two major landscape types over time within a first‐order Arctic watershed. The depth position and thickness of the saturated zone is the dominant control of groundwater flow variability between sites and during different times of year. The effect of water table depth on groundwater flow dwarfs the effect of thaw depth. In landscapes with low land‐surface slopes (2–4%), a combination of higher water tables and thicker, permeable peat deposits cause relatively constant groundwater flows between the early and late thawed seasons. Landscapes with larger land‐surface slopes (4–10%) have both deeper water tables and thinner peat deposits; here the commonly observed permeability decrease with depth is more pronounced than in flatter areas, and groundwater flows decrease significantly between early and late summer as the water table drops. Groundwater flows are also affected by microtopographic features that retain groundwater that could otherwise be released as the active layer deepens. The dominant sources of groundwater, and thus dissolved organic matter, are likely wet, flatter regions with thick organic layers. This finding informs fluid flow and solute transport dynamics for the present and future Arctic

Measurement of interfacial tension of immiscible liquid pairs in microgravity

A discussion is given of a containerless microgravity experiment aimed at measuring the interfacial tension of immiscible liquid pairs using a compound drop rotation method. The reasons for the failure to execute such experiments in microgravity are described. Also, the results of post-flight analyses used to confirm our arguments are presented

Groundwater Flow and Exchange Across the Land Surface Explain Carbon Export Patterns in Continuous Permafrost Watersheds

Groundwater flow regimes in the seasonally thawed soils in areas of continuous permafrost are relatively unknown despite their potential role in delivering water, carbon, and nutrients to streams. Using numerical groundwater flow models informed by observations from a headwater catchment in arctic Alaska, United States, we identify several mechanisms that result in substantial surface‐subsurface water exchanges across the land surface during downslope transport and create a primary control on dissolved organic carbon loading to streams and rivers. The models indicate that surface water flowing downslope has a substantial groundwater component due to rapid surface‐subsurface exchanges across a range of hydrologic states, from unsaturated to flooded. Field‐based measurements corroborate the high groundwater contributions, and river dissolved organic carbon concentrations are similar to that of groundwater across large discharge ranges. The persistence of these groundwater contributions in arctic watersheds will influence carbon export to rivers as thaw depth increases in a warmer climate

Groundwater Flow and Exchange Across the Land Surface Explain Carbon Export Patterns in Continuous Permafrost Watersheds

Groundwater flow regimes in the seasonally thawed soils in areas of continuous permafrost are relatively unknown despite their potential role in delivering water, carbon, and nutrients to streams. Using numerical groundwater flow models informed by observations from a headwater catchment in arctic Alaska, United States, we identify several mechanisms that result in substantial surface‐subsurface water exchanges across the land surface during downslope transport and create a primary control on dissolved organic carbon loading to streams and rivers. The models indicate that surface water flowing downslope has a substantial groundwater component due to rapid surface‐subsurface exchanges across a range of hydrologic states, from unsaturated to flooded. Field‐based measurements corroborate the high groundwater contributions, and river dissolved organic carbon concentrations are similar to that of groundwater across large discharge ranges. The persistence of these groundwater contributions in arctic watersheds will influence carbon export to rivers as thaw depth increases in a warmer climate