The cloquet forest

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Satellite gravity – enhancements from new satellites and new altimeter technology

This paper reviews the impacts of new satellite altimeter data sets and new technology on the production of satellite gravity. It considers the contribution of the increased data volume, the application of new altimeter acquisition technology and the potential for future developments. Satellite altimeter derived gravity has provided gravity maps of the world's seas since the 1980s, but, from 1995 to 2010, virtually all improvements were in the processing as there were no new satellite data with closely spaced tracks. In recent years, new data from CryoSat‐2 (launched in 2010) and the geodetic mission of Jason‐1 (2012–2013) have provided a wealth of additional coverage and new technology allows further improvements. The synthetic aperture radar mode of CryoSat‐2 uses a scanning approach to limit the size of the altimeter sea surface footprint in the along‐track direction. Tests indicate that this allows reliable data to be acquired closer to coastlines. The synthetic aperture radar interferometric mode of CryoSat‐2 uses two altimeters to locate sea‐surface reflection points laterally away from the satellite track. In a study to generate gravity for freshwater lakes, this mode is found to be valuable in extending the available satellite coverage. The AltiKa altimeter uses higher frequency radar to provide less noisy sea‐surface signals and its new orbit mode gives potential for further improvements in satellite gravity. Future developments include the potential for swath mapping to provide further gravity improvements

Mapping the depth to magnetic basement using inversion of pseudogravity: Application to the Bishop model and the Stord Basin, northern North Sea

Magnetic depth estimation methods are routinely used to map the depth of sedimentary basins by assuming that the sediments are nonmagnetic and underlain by magnetic basement rocks. Most of these methods generate basement depth estimates at discrete points. Converting these depth estimates into a grid or map form often requires the application of qualitative methods. The reason for this is twofold: first, in deeper parts of basins, there is generally a scarcity of depth estimates and those that have been determined tend to be biased toward the shallower basement structures close to the basin edge; and second, depth estimates intrinsically relate to magnetic anomalies that emanate from the top edges of basement faults/contacts resulting in a shallow depth bias. Thus, simple grid interpolation of these depth estimates often forms a shallower and structurally unrepresentative map when evaluated in detail. To overcome these problems of qualitative and/or simple grid interpolation of these point-depth estimates into a regular grid, we use the pseudogravity field transform response of the magnetic field to constrain this interpolation using inversion methods together with the relationship between the point-depth estimates and their pseudogravity values. The pseudogravity transformation converts a grid of magnetic data such that the resulting grid has the same simple relationship to magnetic susceptibility that a gravity grid has to density. The pseudogravity map is thus straightforward to visualize in terms of basement structure, but it only maps the magnetic properties of the subsurface and is not related to the gravity anomaly or the density. We describe a practical approach to invert pseudogravity grids using gravity inversion software to produce a 3D basin model assuming a constant susceptibility basement. The approach is initially tested on the Bishop 3D model and then applied to an example from the northern North Sea. This approach can be considered complementary to 3D gravity inversion and has the advantage that the pseudogravity response is not affected by structure within the sediments or effects such as sediment compaction, inversion, or isostatic compensation, all of which often complicate the gravity response of sedimentary basins

Successful adaptation of 3D inversion methodologies for archaeological-scale, total field magnetic datasets

Despite the development of advanced processing and interpretation tools for magnetic datasets in the fields of mineral and hydrocarbon industries, these methods have not achieved similar levels of adoption for archaeological or very near surface surveys. Using a synthetic dataset we demonstrate that certain methodologies and assumptions used to successfully invert more regional-scale data can lead to large discrepancies between the true and recovered depths when applied to archaeological-type anomalies. We propose variations to the current approach, analysing the choice of the depthweighting function, mesh design and parameter constraints, to develop an appropriate technique for the 3D inversion of archaeological scale datasets. The results show a successful recovery of a synthetic scenario, as well as a case study of a Romano-Celtic temple in the UK. For the case study, the final susceptibility model is compared with two coincident ground penetrating radar surveys, showing a high correlation with the comparative depth slices. The new approach takes interpretation of archaeological datasets beyond a simple 2D visual interpretation based on pattern recognition

Interest in and barriers to practicing yoga among family caregivers of people with cancer

Background: Family caregivers of people with cancer report high levels of psychological distress. Yoga, with well-documented mental health benefits, could be a useful intervention to address distress in this population. However, little is known about yoga practices among cancer caregivers. The present study evaluates their interest in and barriers to yoga practice. Methods: We conducted a cross-sectional survey study of family caregivers of cancer patients at five suburban satellite locations of an academic cancer center. Survey items and statistical analyses focused on yoga usage as well as interest in and barriers to yoga practice. Results: Among 539 participants, most were females (64.8%), white (84.2%), and caring for a spouse or partner (54.7%). Interest in practicing yoga among study participants was 42.3%. Increased interest was independently associated with being females (odds ratio [OR] = 3.30, 95% confidence interval [CI] = 1.98–5.51, P < 0.001) and employed (part-time: OR = 2.58, 95% CI = 1.1–6.18, P = 0.03; full-time: OR = 1.77, 95% CI = 1.1–2.01, P = 0.02). Few participants (6.3%) were currently practicing yoga, although 31% had done so in the past. Sixty-one percent of those who had practiced before their loved one's diagnosis stopped practicing yoga afterward. Commonly cited barriers to yoga practice included time constraints (37.3%) and psychological obstacles (33.6%). About a quarter of those who had never practiced yoga lacked awareness of yoga's benefits (26.6%). Conclusion: Despite the low use of yoga, interest in practicing was moderately high, especially among women and employed caregivers. As caregivers face numerous barriers to yoga practice, strategies are needed to overcome these barriers and help them access yoga's health benefits