A pseudo-spectral method for simulating of poro-elastic seismic wave propagation in complex borehole environments

We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in cylindrical coordinates. An important application of this method is the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh consisting of three concentric domains representing the borehole fluid in the center, the borehole casing and the surrounding porous formation. The spatial discretization is based on a Chebyshev expansion in the radial direction, Fourier expansions in the other directions, and a Runge-Kutta integration scheme for the time evolution. A domain decomposition method based on the method of characteristics is used to match the boundary conditions at the fluid/porous-solid and porous-solid/porous-solid interfaces. The viability and accuracy of the proposed method has been tested and verified in 2D polar coordinates through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently benchmarked solution for 2D Cartesian coordinates. The proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is handled adequately.

Editorial research and the publication process in biomedicine and health: Report from the Esteve Foundation Discussion Group, December 2012.

Despite the fact that there are more than twenty thousand biomedical journals in the world, research into the work of editors and publication process in biomedical and health care journals is rare. In December 2012, the Esteve Foundation, a non-profit scientific institution that fosters progress in pharmacotherapy by means of scientific communication and discussion organized a discussion group of 7 editors and/or experts in peer review biomedical publishing. They presented findings of past editorial research, discussed the lack of competitive funding schemes and specialized journals for dissemination of editorial research, and reported on the great diversity of misconduct and conflict of interest policies, as well as adherence to reporting guidelines. Furthermore, they reported on the reluctance of editors to investigate allegations of misconduct or increase the level of data sharing in health research. In the end, they concluded that if editors are to remain gatekeepers of scientific knowledge they should reaffirm their focus on the integrity of the scientific record and completeness of the data they publish. Additionally, more research should be undertaken to understand why many journals are not adhering to editorial standards, and what obstacles editors face when engaging in editorial research.

Official Positions for FRAX® clinical regarding smoking from Joint Official Positions Development Conference of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX®.

The worldwide prevalence of smoking has been estimated at about 50% in men, and 10% in women, with larger variations among different populations studied. Smoking has been shown to affect many organ systems resulting in severe morbidity and increased mortality. In addition, smoking has been identified as a predictor of ten-year fracture risk in men and women, largely independent of an individual's bone mineral density. This finding has eventually lead to incorporation of this risk factor into FRAX®, an algorithm that has been developed to calculate an individual's ten-year fracture risk. However, only little, or conflicting data is available on a possible association between smoking dose, duration, length of time after cessation, type of tobacco and fracture risk, limiting this risk factor's applicability in the context of FRAX®.

Joint Official Positions of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX(®). Executive Summary of the 2010 Position Development Conference on Interpretation and use of FRAX® in clinical practice.

The International Society for Clinical Densitometry (ISCD) and the International Osteoporosis Foundation (IOF) convened the FRAX(®) Position Development Conference (PDC) in Bucharest, Romania, on November 14, 2010, following a two-day joint meeting of the ISCD and IOF on the "Interpretation and Use of FRAX(®) in Clinical Practice." These three days of critical discussion and debate, led by a panel of international experts from the ISCD, IOF and dedicated task forces, have clarified a number of important issues pertaining to the interpretation and implementation of FRAX(®) in clinical practice. The Official Positions resulting from the PDC are intended to enhance the quality and clinical utility of fracture risk assessment worldwide. Since the field of skeletal assessment is still evolving rapidly, some clinically important issues addressed at the PDCs are not associated with robust medical evidence. Accordingly, some Official Positions are based largely on expert opinion. Despite limitations inherent in such a process, the ISCD and IOF believe it is important to provide clinicians and technologists with the best distillation of current knowledge in the discipline of bone densitometry and provide an important focus for the scientific community to consider. This report describes the methodology and results of the ISCD-IOF PDC dedicated to FRAX(®).

FRAX(®) Bone Mineral Density Task Force of the 2010 Joint International Society for Clinical Densitometry International Osteoporosis Foundation Position Development Conference.

FRAX(®) is a fracture risk assessment algorithm developed by the World Health Organization in cooperation with other medical organizations and societies. Using easily available clinical information and femoral neck bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DXA), when available, FRAX(®) is used to predict the 10-year probability of hip fracture and major osteoporotic fracture. These values may be included in country specific guidelines to aid clinicians in determining when fracture risk is sufficiently high that the patient is likely to benefit from pharmacological therapy to reduce that risk. Since the introduction of FRAX(®) into clinical practice, many practical clinical questions have arisen regarding its use. To address such questions, the International Society for Clinical Densitometry (ISCD) and International Osteoporosis Foundations (IOF) assigned task forces to review the best available medical evidence and make recommendations for optimal use of FRAX(®) in clinical practice. Questions were identified and divided into three general categories. A task force was assigned to investigating the medical evidence in each category and developing clinically useful recommendations. The BMD Task Force addressed issues that included the potential use of skeletal sites other than the femoral neck, the use of technologies other than DXA, and the deletion or addition of clinical data for FRAX(®) input. The evidence and recommendations were presented to a panel of experts at the ISCD-IOF FRAX(®) Position Development Conference, resulting in the development of ISCD-IOF Official Positions addressing FRAX(®)-related issues.

Constraints on the permeability structure of alluvial aquifers from the poro-elastic inversion of multi-frequency P-wave velocity logs

We have explored the possibility of obtaining first-order permeability estimates for saturated alluvial sediments based on the poro-elastic interpretation of the P-wave velocity dispersion inferred from sonic logs. Modern sonic logging tools designed for environmental and engineering applications allow one for P-wave velocity measurements at multiple emitter frequencies over a bandwidth covering 5 to 10 octaves. Methodological considerations indicate that, for saturated unconsolidated sediments in the silt to sand range and typical emitter frequencies ranging from approximately 1 to 30 kHz, the observable velocity dispersion should be sufficiently pronounced to allow one for reliable first-order estimations of the permeability structure. The corresponding predictions have been tested on and verified for a borehole penetrating a typical surficial alluvial aquifer. In addition to multifrequency sonic logs, a comprehensive suite of nuclear and electrical logs, an S-wave log, a litholog, and a limited number laboratory measurements of the permeability from retrieved core material were also available. This complementary information was found to be essential for parameterizing the poro-elastic inversion procedure and for assessing the uncertainty and internal consistency of corresponding permeability estimates. Our results indicate that the thus obtained permeability estimates are largely consistent with those expected based on the corresponding granulometric characteristics, as well as with the available evidence form laboratory measurements. These findings are also consistent with evidence from ocean acoustics, which indicate that, over a frequency range of several orders-of-magnitude, the classical theory of poro-elasticity is generally capable of explaining the observed P-wave velocity dispersion in medium- to fine-grained seabed sediments

Official Positions for FRAX® clinical regarding rheumatoid arthritis from Joint Official Positions Development Conference of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX®.

Rheumatoid arthritis is the only secondary cause of osteoporosis that is considered independent of bone density in the FRAX(®) algorithm. Although input for rheumatoid arthritis in FRAX(®) is a dichotomous variable, intuitively, one would expect that more severe or active disease would be associated with a greater risk for fracture. We reviewed the literature to determine if specific disease parameters or medication use could be used to better characterize fracture risk in individuals with rheumatoid arthritis. Although many studies document a correlation between various parameters of disease activity or severity and decreased bone density, fewer have associated these variables with fracture risk. We reviewed these studies in detail and concluded that disability measures such as HAQ (Health Assessment Questionnaire) and functional class do correlate with clinical fractures but not morphometric vertebral fractures. One large study found a strong correlation with duration of disease and fracture risk but additional studies are needed to confirm this. There was little evidence to correlate other measures of disease such as DAS (disease activity score), VAS (visual analogue scale), acute phase reactants, use of non-glucocorticoid medications and increased fracture risk. We concluded that FRAX(®) calculations may underestimate fracture probability in patients with impaired functional status from rheumatoid arthritis but that this could not be quantified at this time. At this time, other disease measures cannot be used for fracture prediction. However only a few, mostly small studies addressed other disease parameters and further research is needed. Additional questions for future research are suggested.

Official Positions for FRAX® clinical regarding biochemical markers from Joint Official Positions Development Conference of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX®.

The best indirect evidence that increased bone turnover contributes to fracture risk is the fact that most of the proven therapies for osteoporosis are inhibitors of bone turnover. The evidence base that we can use biochemical markers of bone turnover in the assessment of fracture risk is somewhat less convincing. This relates to natural variability in the markers, problems with the assays, disparity in the statistical analyses of relevant studies and the independence of their contribution to fracture risk. More research is clearly required to address these deficiencies before biochemical markers might contribute a useful independent risk factor for inclusion in FRAX(®).

Official Positions for FRAX® clinical regarding falls and frailty: can falls and frailty be used in FRAX®? From Joint Official Positions Development Conference of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX®.

Risk factors for fracture can be purely skeletal, e.g., bone mass, microarchitecture or geometry, or a combination of bone and falls risk related factors such as age and functional status. The remit of this Task Force was to review the evidence and consider if falls should be incorporated into the FRAX® model or, alternatively, to provide guidance to assist clinicians in clinical decision-making for patients with a falls history. It is clear that falls are a risk factor for fracture. Fracture probability may be underestimated by FRAX® in individuals with a history of frequent falls. The substantial evidence that various interventions are effective in reducing falls risk was reviewed. Targeting falls risk reduction strategies towards frail older people at high risk for indoor falls is appropriate. This Task Force believes that further fracture reduction requires measures to reduce falls risk in addition to bone directed therapy. Clinicians should recognize that patients with frequent falls are at higher fracture risk than currently estimated by FRAX® and include this in decision-making. However, quantitative adjustment of the FRAX® estimated risk based on falls history is not currently possible. In the long term, incorporation of falls as a risk factor in the FRAX® model would be ideal.

Etude prospective d'évaluation psychiatrique et pédagogique dans un service pour adolescents de la Fondation Santé des Etudiants de France. Méthodologie et résultats préliminaires [Prospective study of psychiatric and pedagogic evaluation of the adolescent service of the Student Health Foundation of France. Methodology and preliminary results].

The present prospective study, with a five-year follow-up, presents an extensive psychiatric and educational assessment of an adolescent population (N = 30) in the age range 14-20, suffering from several psychiatric disorders, though apt to follow a normal academic program. The residential settings where the study took place provide both psychiatric and schooling facilities. In this environment, what is the effectiveness of long-term hospitalization? Are there any criteria for predicting results? After discharge, could social adjustments difficulties be prevented? Assessment instruments are described and the results of one preliminary study are presented. The actual data seems to confirm the impact of the special treatment facilities combining schooling and psychiatric settings on the long term outcome of adolescents.

Quantitative comparison between simulations of seismic wave propagation in heterogeneous poro-elastic media and equivalent visco-elastic solids for marine-type environments

There is increasing evidence to suggest that the presence of mesoscopic heterogeneities constitutes an important seismic attenuation mechanism in porous rocks. As a consequence, centimetre-scale perturbations of the rock physical properties should be taken into account for seismic modelling whenever detailed and accurate responses of specific target structures are desired, which is, however, computationally prohibitive. A convenient way to circumvent this problem is to use an upscaling procedure to replace each of the heterogeneous porous media composing the geological model by corresponding equivalent visco-elastic solids and to solve the visco-elastic equations of motion for the inferred equivalent model. While the overall qualitative validity of this procedure is well established, there are as of yet no quantitative analyses regarding the equivalence of the seismograms resulting from the original poro-elastic and the corresponding upscaled visco-elastic models. To address this issue, we compare poro-elastic and visco-elastic solutions for a range of marine-type models of increasing complexity. We found that despite the identical dispersion and attenuation behaviour of the heterogeneous poro-elastic and the equivalent visco-elastic media, the seismograms may differ substantially due to diverging boundary conditions, where there exist additional options for the poro-elastic case. In particular, we observe that at the fluid/porous-solid interface, the poro- and visco-elastic seismograms agree for closed-pore boundary conditions, but differ significantly for open-pore boundary conditions. This is an important result which has potentially far-reaching implications for wave-equation-based algorithms in exploration geophysics involving fluid/porous-solid interfaces, such as, for example, wavefield decomposition.

Official Positions for FRAX® clinical regarding prior fractures from Joint Official Positions Development Conference of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX®.

The 2010 Position Development Conference addressed four questions related to the impact of previous fractures on 10-year fracture risk as calculated by FRAX(®). To address these questions, PubMed was searched on the keywords "fracture, epidemiology, osteoporosis." Titles of retrieved articles were reviewed for an indication that risk for future fracture was discussed. Abstracts of these articles were reviewed for an indication that one or more of the questions listed above was discussed. For those that did, the articles were reviewed in greater detail to extract the findings and to find additional past work and citing works that also bore on the questions. The official positions and the supporting literature review are presented here. FRAX(®) underestimates fracture probability in persons with a history of multiple fractures (good, A, W). FRAX(®) may underestimate fracture probability in individuals with prevalent severe vertebral fractures (good, A, W). While there is evidence that hip, vertebral, and humeral fractures appear to confer greater risk of subsequent fracture than fractures at other sites, quantification of this incremental risk in FRAX(®) is not possible (fair, B, W). FRAX(®) may underestimate fracture probability in individuals with a parental history of non-hip fragility fracture (fair, B, W). Limitations of the methodology include performance by a single reviewer, preliminary review of the literature being confined to titles, and secondary review being limited to abstracts. Limitations of the evidence base include publication bias, overrepresentation of persons of European descent in the published studies, and technical differences in the methods used to identify prevalent and incident fractures. Emerging topics for future research include fracture epidemiology in non-European populations and men, the impact of fractures in family members other than parents, and the genetic contribution to fracture risk.

Official Positions for FRAX® Bone Mineral Density and FRAX® simplification from Joint Official Positions Development Conference of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX®.

Tools to predict fracture risk are useful for selecting patients for pharmacological therapy in order to reduce fracture risk and redirect limited healthcare resources to those who are most likely to benefit. FRAX® is a World Health Organization fracture risk assessment algorithm for estimating the 10-year probability of hip fracture and major osteoporotic fracture. Effective application of FRAX® in clinical practice requires a thorough understanding of its limitations as well as its utility. For some patients, FRAX® may underestimate or overestimate fracture risk. In order to address some of the common issues encountered with the use of FRAX® for individual patients, the International Society for Clinical Densitometry (ISCD) and International Osteoporosis Foundation (IOF) assigned task forces to review the medical evidence and make recommendations for optimal use of FRAX® in clinical practice. Among the issues addressed were the use of bone mineral density (BMD) measurements at skeletal sites other than the femoral neck, the use of technologies other than dual-energy X-ray absorptiometry, the use of FRAX® without BMD input, the use of FRAX® to monitor treatment, and the addition of the rate of bone loss as a clinical risk factor for FRAX®. The evidence and recommendations were presented to a panel of experts at the Joint ISCD-IOF FRAX® Position Development Conference, resulting in the development of Joint ISCD-IOF Official Positions addressing FRAX®-related issues.