Marketing and clinical trials: a case study Francis, David; Roberts, Ian; Elbourne, Diana R ...
Current controlled trials in cardiovascular medicine,
11/2007, Volume:
8, Issue:
1
Journal Article
Peer reviewed
Open access
Publicly funded clinical trials require a substantial commitment of time and money. To ensure that sufficient numbers of patients are recruited it is essential that they address important questions ...in a rigorous manner and are managed well, adopting effective marketing strategies.
Using methods of analysis drawn from management studies, this paper presents a structured assessment framework or reference model, derived from a case analysis of the MRC's CRASH trial, of 12 factors that may affect the success of the marketing and sales activities associated with clinical trials.
The case study demonstrates that trials need various categories of people to buy in - hence, to be successful, trialists must embrace marketing strategies to some extent.
The performance of future clinical trials could be enhanced if trialists routinely considered these factors.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
ABSTRACT
Surface nuclear magnetic resonance (NMR) is a non‐invasive geophysical method that can provide valuable information about aquifer properties related to groundwater flow and storage. Our ...ability to extract such information from surface NMR data, however, is limited by an insufficient understanding of the relaxation parameter T2* governing the decay rate of the surface NMR signal in Earth’s magnetic field. In this study, we use a combination of numerical and laboratory experiments to systematically explore the effect of two key geologic properties, pore size and magnetic susceptibility, on the T2* relaxation process. A one‐dimensional numerical model is developed and parametrized to simulate the surface NMR response for a wide range of geologic materials. These simulations illuminate the processes controlling T2* relaxation and identify conditions under which T2* exhibits varied sensitivity to pore size. For materials with low magnetic susceptibility, T2* is highly sensitive to pore size; however, as susceptibility increases, this sensitivity diminishes and T2* becomes dominated by complex dephasing effects, particularly when pores are large. Laboratory Earth’s field NMR experiments complement the numerical simulations. Measurements on water‐saturated quartz sands show that for weakly magnetic materials, T2* can be sensitive to pore size and thus could provide useful information about aquifer properties.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Accurate and timely estimates of groundwater storage changes are critical to the sustainable management of aquifers worldwide, but are hindered by the lack of in-situ groundwater measurements in most ...regions. Hydrologic remote sensing measurements provide a potential pathway to quantify groundwater storage changes by closing the water balance, but the degree to which remote sensing data can accurately estimate groundwater storage changes is unclear. In this study, we quantified groundwater storage changes in California's Central Valley at two spatial scales for the period 2002 through 2020 using remote sensing data and an ensemble water balance method. To evaluate performance, we compared estimates of groundwater storage changes to three independent estimates: GRACE satellite data, groundwater wells and a groundwater flow model. Results suggest evapotranspiration has the highest uncertainty among water balance components, while precipitation has the lowest. We found that remote sensing-based groundwater storage estimates correlated well with independent estimates; annual trends during droughts fall within 15% of trends calculated using wells and groundwater models within the Central Valley. Remote sensing-based estimates also reliably estimated the long-term trend, seasonality, and rate of groundwater depletion during major drought events. Additionally, our study suggests that the proposed method estimate changes in groundwater at sub-annual latencies, which is not currently possible using other methods. The findings have implications for improving the understanding of aquifer dynamics and can inform regional water managers about the status of groundwater systems during droughts.
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•Groundwater storage changes estimated using ensemble remote sensing water balance.•Remote sensing-based method can provide reliable estimates of changes in storage.•Long-term changes in groundwater storage during droughts were well captured.•Uncertainty is highest in the water balance component evapotranspiration.•Remote sensing data allow groundwater storage estimates at sub-annual timescales.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Ground‐penetrating radar (GPR) can be used to obtain information about the variation in the dielectric constant of the subsurface. The sensitivity of a soil's dielectric constant to the presence of ...water therefore makes water content estimation by GPR possible. The dielectric constant derived from GPR data, however, is also influenced by the geometric distribution of water in the subsurface. We show that this causes the relationship between the dielectric constant and water content to become scale dependent in complex geologic systems. We have derived dielectric constant‐water content relationships that account for subsurface geometries in spatially correlated random media that can be characterized using geostatistics. From these relationships we illustrate that the importance of scale effects are strongly dependent on the variance and the anisotropy of the water content in the subsurface; in some cases, ignoring scale effects will not significantly impact the estimation of water content, while in other cases, large biases can occur. This work provides a conceptual framework for the predictive modeling of field‐scale dielectric constant‐water content relationships.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We present a 2.5-D forward modeling algorithm for electrical resistivity data. The algorithm incorporates a boundary condition and source singularity correction that greatly reduces the need to pad ...the model space. In addition, the algorithm includes an optimization method for estimating the appropriate Fourier coefficients to achieve an accurate 2.5-D approximation. The optimization scheme uses a gradient-based search to find the optimal coefficients. We compare results from our algorithm to two analytical solutions. We are able to achieve errors on the order 1% when compared to these models. We have implemented the algorithm as an open source MATLAB-based forward modeling package. The MATLAB code is useful for exploring subsurface current flow. It has been coded so that it can be easily ported to work with inversion routines. The code is computationally efficient and suitable for solving 2-D problems with a large number of model parameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The passage of the Sustainable Groundwater Management Act in California has highlighted a need for cost‐effective ways to acquire the data used in building conceptual models of the aquifer systems in ...the Central Valley of California. One approach would be the regional implementation of the airborne electromagnetic (AEM) method. We acquired 104 line‐kilometers of data in the Tulare Irrigation District, in the Central Valley, to determine the depth of investigation (DOI) of the AEM method, given the abundance of electrically conductive clays, and to assess the usefulness of the method for mapping the hydrostratigraphy. The data were high quality providing, through inversion of the data, models displaying the variation in electrical resistivity to a depth of approximately 500 m. In order to transform the resistivity models to interpreted sections displaying lithology, we established the relationship between resistivity and lithology using collocated lithology logs (from drillers' logs) and AEM data. We modeled the AEM response and employed a bootstrapping approach to solve for the range of values in the resistivity model corresponding to sand and gravel, mixed coarse and fine, and clay in the unsaturated and saturated regions. The comparison between the resulting interpretation and an existing cross section demonstrates that AEM can be an effective method for mapping the large‐scale hydrostratigraphy of aquifer systems in the Central Valley. The methods employed and developed in this study have widespread application in the use of the AEM method for groundwater management in similar geologic settings.
Article impact statement: Airborne electromagnetic data provide the critical information needed to develop conceptual models of the aquifer systems in the Central Valley of California.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In this multicenter trial, higher-risk adults undergoing on-pump CABG (with or without valve surgery) were randomly assigned to preconditioning with transient arm ischemia and reperfusion or sham ...conditioning. Remote ischemic preconditioning did not improve clinical outcomes.
Coronary heart disease is the leading cause of death and disability worldwide. For patients with multivessel coronary artery disease, the treatment of choice for many is revascularization by means of coronary-artery bypass grafting (CABG) surgery. As a result of the aging of the population, an increased prevalence of coexisting conditions (e.g., diabetes, obesity, and hypertension), and a growing need for concomitant valve surgery, higher-risk patients are undergoing CABG surgery (with or without valve surgery); the clinical outcomes in such patients have been worse than the outcomes in patients without so many problems.
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Thus, novel cardioprotective interventions are indicated to . . .
The Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) has provided a valuable precipitation dataset for hydrometeorological studies (1998–2015). However, TMPA ...shows some differences when compared to the ground-based estimates. In this study, a correction model is developed to improve the accuracy of the TRMM precipitation monthly product by reducing the bias compared to the ground-based estimates. The TRMM 3B43 precipitation product is compared with the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) and with gridded precipitation estimates acquired from the CPC Unified Precipitation Project, two ground-based precipitation estimates, in the conterminous United States. The bias between the satellite and ground-based estimates is compared with mean surface temperature and elevation, respectively. A weak linear relationship is observed between the bias and temperature but a moderate inverse linear relationship is observed between the bias and elevation. Based on these observations, a linear model is developed for the TRMM 3B43–PRISM bias and elevation. The developed model is calibrated and validated using Monte Carlo cross validation with 25% of the available data as a calibration set and the remaining 75% of the data as a validation set. The estimatedmodel parameters are then used in a correction formula for the TRMM 3B43 dataset for elevations above 1500 m above mean sea level. The corrected TRMM 3B43 product is verified for the high-elevation regions over the entire United States as well as in two high-elevation local regions in the western United States. The results show a significant improvement in the accuracy of the monthly satellite product in the high elevations of the United States.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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