590 research outputs found
Sharing privacy-sensitive access to neuroimaging and genetics data: a review and preliminary validation
No full textThe growth of data sharing initiatives for neuroimaging and genomics represents an exciting opportunity to confront the “small N” problem that plagues contemporary neuroimaging studies while further understanding the role genetic markers play in the function of the brain. When it is possible, open data sharing provides the most benefits. However, some data cannot be shared at all due to privacy concerns and/or risk of re-identification. Sharing other data sets is hampered by the proliferation of complex data use agreements (DUAs) which preclude truly automated data mining. These DUAs arise because of concerns about the privacy and confidentiality for subjects; though many do permit direct access to data, they often require a cumbersome approval process that can take months. An alternative approach is to only share data derivatives such as statistical summaries—the challenges here are to reformulate computational methods to quantify the privacy risks associated with sharing the results of those computations. For example, a derived map of gray matter is often as identifiable as a fingerprint. Thus alternative approaches to accessing data are needed. This paper reviews the relevant literature on differential privacy, a framework for measuring and tracking privacy loss in these settings, and demonstrates the feasibility of using this framework to calculate statistics on data distributed at many sites while still providing privacy.This document is protected by copyright and was first published by Frontiers. All rights reserved. It is reproduced with permission.Peer reviewe
Modeling the growth and dissolution of clots in flowing blood
Get PDFMultiple interacting mechanisms control the formation and dissolution of clots to
maintain blood in a state of delicate balance. In addition to a myriad of biochemical
reactions, rheological factors also play a crucial role in modulating the response of
blood to external stimuli. The broad stimuli for clot formation were laid out, more
than a century ago, in, what is now referred to as, Virchow��������s triad. To date, a
comprehensive model for clot formation and dissolution, that takes into account the
biochemical, medical and rheological factors, has not been put into place, the existing
models emphasizing either one or the other of the factors. In this dissertation, a model
is developed for clot formation and dissolution that incorporates many of the relevant
crucial factors that have a bearing on the problem. The model, though just a first step
towards understanding a complex phenomenon goes further than previous models in
integrating the biochemical, medical and rheological factors that come into play. The
model is tested in some simple flow situations as part of an attempt to elucidate
Virchow��������s triad. Extensions to the model, along with detailed numerical studies, will
hopefully aid in a clearer understanding of the phenomenon, and in making relevant
clinical correlations
COINSTAC: A Privacy Enabled Model and Prototype for Leveraging and Processing Decentralized Brain Imaging Data
No full textThe field of neuroimaging has embraced the need for sharing and collaboration. Data sharing mandates from public funding agencies and major journal publishers have spurred the development of data repositories and neuroinformatics consortia. However, efficient and effective data sharing still faces several hurdles. For example, open data sharing is on the rise but is not suitable for sensitive data that are not easily shared, such as genetics. Current approaches can be cumbersome (such as negotiating multiple data sharing agreements). There are also significant data transfer, organization and computational challenges. Centralized repositories only partially address the issues. We propose a dynamic, decentralized platform for large scale analyses called the Collaborative Informatics and Neuroimaging Suite Toolkit for Anonymous Computation (COINSTAC). The COINSTAC solution can include data missing from central repositories, allows pooling of both open and “closed” repositories by developing privacy-preserving versions of widely-used algorithms, and incorporates the tools within an easy-to-use platform enabling distributed computation. We present an initial prototype system which we demonstrate on two multi-site data sets, without aggregating the data. In addition, by iterating across sites, the COINSTAC model enables meta-analytic solutions to converge to “pooled-data” solutions (i.e., as if the entire data were in hand). More advanced approaches such as feature generation, matrix factorization models, and preprocessing can be incorporated into such a model. In sum, COINSTAC enables access to the many currently unavailable data sets, a user friendly privacy enabled interface for decentralized analysis, and a powerful solution that complements existing data sharing solutions.Peer reviewe
Infrastructure finance : issues, institutions, and policies
Get PDFThe author analyzes the distinctive features of formal and informal financing of infrastructure and the principal issues policymakers must address in dealing with infrastructure finance: its adequacy in competitive financial systems, its budgetary vulnerability, the rationale for foreign finance, the role of user charges and taxes, the pros and cons of earmarking taxes, the institutional framework for infrastructure finance, the role of municipal finance, different approaches to the private financing of infrastructure (such as franchises, leases, management contracts, and consumer cooperatives), the critical role of contractor finance, and informal financing of infrastructure.The author concludes the following points. Not only the amount of funds but the regularity of their flow is central to maintaining infrastructure. But infrastructure must compete on a level playing field with other sectors. Any essential (but not open-ended) subsidies for maintaining universal minimum standards of service are best carried on the government budget, subject to periodic review. Institutional reform is needed to rationalize the division of resources and responsibilities among all layers of government and to provide mechanisms for insulating infrastructure finance from budgetary and other pressures. Such mechanisms include earmarking, privatization, and objective criteria for sharing value-added tax and other national tax revenue. Most developing countries do not have a national infrastructure agency to fund and coordinate technical assistance for infrastructure projects. The author makes a case for an apex financial entity in charge of municipal financial intermediaries for infrastructure, pointing to the instructive experience of intermediaries in Colombia and Jordan. One responsibility of such an agency would be to determine the necessary import content (for equipment, technical, and managerial expertise) of infrastructure finance, to prevent overborrowing. Privatization of infrastructure should be viewed as implicit earmarking, but official regulation of public utility prices should allow private utilities to generate retained earnings (to encourage self-financing) and should allow adjustments for inflation and exchange rate fluctuations. Infrastructure policy should allow for cost recovery through user charges as well as for tax revenues, especially through municipal taxes, since even the viability of loan finance depends on an efficient tax effort. While infrastructure finance is important, it is not always the decisive constraint, judging from the operating losses of even adequately funded infrastructure projects.Banks&Banking Reform,Public Sector Economics&Finance,Housing Finance,Urban Economics,Public&Municipal Finance
Long-term efficacy and safety of safinamide as add-on therapy in early Parkinson's disease
No full textBackground and purpose: Safinamide is an α-aminoamide with both dopaminergic and non-dopaminergic mechanisms of action in Phase III clinical development as a once-daily add-on to dopamine agonist (DA) therapy for early Parkinson's disease (PD). Methods: Study 017 was a 12-month, randomized, double-blind, placebo-controlled pre-planned extension study to the previously reported Study 015. Patients received safinamide 100 or 200 mg/day or placebo added to a single DA in early PD. The primary efficacy endpoint was the time from baseline (Study 015 randomization) to 'intervention', defined as increase in DA dose; addition of another DA, levodopa or other PD treatment; or discontinuation due to lack of efficacy. Safinamide groups were pooled for the primary efficacy endpoint analysis; post hoc analyses were performed on each separate dose group. Results: Of the 269 patients randomized in Study 015, 227 (84%) enrolled in Study 017 and 187/227 (82%) patients completed the extension study. Median time to intervention was 559 and 466 days in the pooled safinamide and placebo groups, respectively (log-rank test; P = 0.3342). In post hoc analyses, patients receiving safinamide 100 mg/day experienced a significantly lower rate of intervention compared with placebo (25% vs. 51%, respectively) and a delay in median time to intervention of 9 days (P < 0.05; 240- to 540-day analysis). Conclusions: The pooled data from the safinamide groups failed to reach statistical significance for the primary endpoint of median time from baseline to additional drug intervention. Post hoc analyses indicate that safinamide 100 mg/day may be effective as add-on treatment to DA in PD. © 2012 The Author(s) European Journal of Neurolog
Study of properties of sand asphalt using a torsional rheometer
Get PDFThe modeling of Sand Asphalt and experiments to measure their rheological properties are of vital concern to many industrial processes especially highway and roadway pavement construction industry. A variety of hot mix asphalt mixtures are used in highway and runway pavement construction, with each mixture catering to a specific need. These mixtures vary in type and percentage of aggregates and asphalt used and consequently exhibit marked differences in their response. The main thrust of this research is to provide experimental data which would be helpful in determining the efficacy of the constitutive models that have been developed for these hot mix asphalt mixtures. Here we attempt to provide experimental data in the raw form for Sand Asphalt mixtures that would be helpful in the theoretical modeling efforts involving asphalt materials using a continuum point of view. For example the data obtained can be of immense help to evaluate the constitutive model developed by Murali Krishnan and Rajagopal. The Sand Asphalt mixture in their model is modeled as `homogenized' single constituent due to the peculiarity of its makeup. The constitutive model of Murali Krishnan and Rajagopal is based on a thermodynamical framework for materials possessing multiple natural configurations (multiple stress free states) to derive the constitutive equations. Recently an Orthogonal Rheometer was built to characterize the granular solids by Gupta and Rajagopal which was later used by Baek in the torsional mode. In this work we have used the same Torsional Rheometer with some minor modifications in the design to measure some general properties of Sand Asphalt mixtures. Sand Asphalt mixtures, due to their non-linear viscoelastic character, exhibit `normal stress effects' and `stress relaxation'. The Rheometer that we used was able to capture these responses with high precision. We have laid out proper procedures for the further testing of asphalt related mixtures. A typical sand asphalt mixture sample in cylindrical shape was used as the test specimen. From this work some interesting data was obtained. A remarkable observation was that as the shear rate is increased, the normal force and torque generated initially decrease, but beyond a certain shear rate they attain a constant value
Biology of insulin-like factor 3 in human reproduction
No full text© The Author 2009. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology.BACKGROUND: Insulin-like factor 3 (INSL3) is a neohormone that has evolved to address specific mammalian traits, in particular, the first phase of testicular descent towards the scrotum during mid-gestation. METHODS: A thorough literature search was made in PubMed using the terms INSL3, as well as the older synonyms RLF and Ley-IL. RESULTS: INSL3 is a major secretory product of the testicular Leydig cells in the fetus and in adult men, and in rodent models, reduction in fetal INSL3 expression is an early marker of the testicular dysgenesis syndrome. In women, it is produced in lower amounts by ovarian theca and luteal cells, and circulating levels are increased in women with polycystic ovarian syndrome. During pregnancy, there is evidence for an interaction regulating the feto-placental unit. The presence of INSL3 in amniocentesis samples taken at 12–14 weeks gestation is absolutely specific for male gender, and levels are predictive of subsequent pre-eclampsia and/or birthweight. INSL3 is also involved in adult traits, such as spermatogenesis and bone metabolism. In adult men, INSL3 is constitutively expressed and secreted into the bloodstream at a constant level, reflecting the number and/or functional capacity of the Leydig cells. In complete contrast, testosterone is highly variable within individuals, is acutely responsive to fluctuations in the hypothalamic–pituitary–gonadal axis and appears to have marginal diagnostic value. INSL3 declines consistently with age in adult men. CONCLUSIONS: INSL3 promises to become an important new diagnostic tool to characterize those men with late-onset hypogonadism and to add clinical diagnostic value at amniocentesis.Richard Ivell and Ravinder Anand-Ivel
Modelling of Ultrasonic Array Signals in Anisotropic Media
No full textThere has been a steady increase of composites and anisotropic materials in primary aircraft structures over the years. This increase is driven by the high strength to weight ratio of such materials leading to lighter and more efficient aircraft. As the uptake of such materials keeps increasing so does the complexity in geometry and manufacture of the parts which use these materials. As in the case of any structural component, these structures suffer from defects during manufacture and from damage inservice and have to be tested using nondestructive methods regularly. A plethora of NDT techniques exist for testing aircraft structures with ultrasonic NDT being a staple in the industry. Testing using single element transducers is being replaced by phased arrays as phased arrays can be used in different testing configurations such as beam steering or using phased arrays to capture the signals and then post process the data to form an image. Phased array testing of isotropic materials has been carried out for a number of years with a lot of research being devoted to the testing of such materials. The testing of isotropic materials is relatively less complicated than for anisotropic materials due to the constant material properties throughout the material, the types of defects or failures which such structures suffer and the effect of the material properties on the ultrasonic beam propagating through it or on the output signals. This leads to a simpler interpretation and easier understanding of results when such structures are tested. On the other hand testing of anisotropic materials is complicated by the fact that the material properties are not the same in every direction. The anisotropic nature of such materials has an effect on the ultrasonic beam propagation and output signals which makes the interpretation and understanding of the output more difficult. The layered structure of the composite materials also leads to multiple reflections and reverberations of the layers during inspection which are properties of the laminate, array parameters etc. leading to noise in the output signals and noise in the image. Due to this ultrasonic NDT remains a bottleneck in the further implementation of composites in aircraft structures. Understanding the effect of these various parameters experimentally would require dozens of experiments with different isolated parameters. To overcome the need for this enormous experimental campaign, modelling and simulations can be carried out to help understand these effects. There has been progress in the NDT community on the adoption of modelling methodologies to simulate the predict the response of the inspected material to the wave passing through it and the output signals which are generated. The numerical models already developed have been applied to a variety of scenarios and to different complex geometries but become quite computationally expensive as the material and inspection procedure complexity increases and take hours of runtime when run on personal computers. Some analytical and semi-analytical models which have been applied are restricted either in geometry, require the numerical evaluation of multiple integrals, are computationally expensive or do not take into consideration the array parameters or are singular when interacting with different geometries.Structural Integrity & Composite
A study of sand-asphalt mixtures: a constitutive model based on a thermomechanical framework and experimental corroboration
Get PDFAsphalt bound mixtures have been put to diverse uses. The complicated nature of
the material and the demanding conditions under which it is used preclude complete
solutions to questions on load bearing capability under field conditions. In proportion
to the quantity of its usage and in acknowledgment of modeling complexity, the
material has been interrogated by many researchers using a variety of mechanical
tests, and a plethora of linear viscoelastic models have been developed. Most models
are intended to account for specific classes of problems.
This work addresses the conspicuous absence of systematic documentation of
normal forces generated as a result of shear. The normal force generated during simple
shear is a clear indication of the nonlinear nature of the material. The effect of fillers
(hydrated lime and limestone), air voids, aggregate gradation, asphalt source and step
loading on normal force generation during torsion is experimentally investigated.
Based on experimental evidence, a non-linear thermomechanical model for sandasphalt
mixtures based on the idea of multiple natural configurations is developed.
The model accounts for the fact that the mixture has a natural configuration (stressfree
configuration) which evolves as it is subjected to loads. Assumptions are made
regarding the manner in which the material stores and dissipates energy. A key assumption is that among the various constitutive relations possible, the one that is
chosen is the one that maximizes the rate of entropy production. The model that is
developed accounts for the anisotropic nature of the response.
The experimental results show that asphalt bound mixtures generate significant
normal forces even at low rotation rates. The source of asphalt, aggregate gradation,
fillers and air voids have a pronounced effect on normal stress generation. The model
is corroborated against data from torsion experiments
Measuring the possibilities of interfuel substitution
Get PDFWhat are the costs of making consumption of production activities use less-polluting fuels? The author reviews how the fuel mix used by different industries has changed over time and examines 2 techniques for estimating the responsiveness of fuel demand to fuel prices: econometric models and the engineering approach. With econometric models, the elasticity of substitution between energy and other inputs determines the costs of making activities less energy-intensive, while the elasticity of substitution between sources of energy (interfuel substitutability) determines the marginal costs of replacing one energy source with another. The engineering approach uses more detailed technical information and can draw a more complete picture, but with less ability to inform about activities with a vast number of different economic agents. Among the author's main conclusions: There are surprisingly large variations in energy and fuel use over time and between countries. Industrial output increased 62 percent in OECD countries between 1971 and 1988, for example, while energy use stayed unchanged. Also, shares of energy sources for industry and electricity vary greatly with local availablity, indicating that these sectors have some flexibility in choice of energy source. A judgment on whether this variability indicates that an economy responds cheaply if energy prices are changed selectively depends on how one reads the more detailed studies in the econometric and engineering literature. Lack of data is the biggest problem in estimating fuel and energy substitutability in non-OECD countries. Engineering studies of fuel switching in industry are rarely available. They exist, however, for the power industry and could be used to estimate the costs of alternative fuel-mixes for particular greenfield sites. The technique could not be used for assessment of economywide policies. Econometric studies are useful inasmuch as they take a sector- or economywide perspective. Econometric techniques are challenging, but often represent the state of the art in providing reliable estimates for elasticies of substitution - particularly when data are scarce and the level of aggregation is high. The issue of whether econometrically estimated structural parameters can be transferred across borders has not been thoroughly investigated.Oil Refining&Gas Industry,Transport and Environment,Energy and Poverty Alleviation,Energy and Environment,Airports and Air Services
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