1,917 research outputs found

    Population-Based Design of Mandibular Fixation Plates with Bone Quality and Morphology Considerations

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    In this paper we present a new population-based implant design methodology, which advances the state-of-the-art approaches by combining shape and bone quality information into the design strategy. The method may enhance the mechanical stability of the fixation and reduces the intra-operative in-plane bending which might impede the functionality of the locking mechanism. The computational method is presented for the case of mandibular locking fixation plates, where the mandibular angle and the bone quality at screw locations are taken into account. The method automatically derives the mandibular angle and the bone thickness and intensity values at the path of every screw from a set of computed tomography images. An optimization strategy is then used to optimize the two parameters of plate angle and screw position. The method was applied to two populations of different genders. Results for the new design are presented along with a comparison with a commercially available mandibular locking fixation plate (MODUS® TriLock® 2.0/2.3/2.5, Medartis AG, Basel, Switzerland). The proposed designs resulted in a statistically significant improvement in the available bone thickness when compared to the standard plate. There is a higher probability that the proposed implants cover areas of thicker cortical bone without compromising the bone mineral density around the screws. The obtained results allowed us to conclude that an angle and screw separation of 129° and 9mm for females and 121° and 10mm for males are more suitable designs than the commercially available 120° and 9m

    Comparative Evaluation of Pelvic Allograft Selection Methods

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    This paper presents a firsthand comparative evaluation of three different existing methods for selecting a suitable allograft from a bone storage bank. The three examined methods are manual selection, automatic volume-based registration, and automatic surface-based registration. Although the methods were originally published for different bones, they were adapted to be systematically applied on the same data set of hemi-pelvises. A thorough experiment was designed and applied in order to highlight the advantages and disadvantages of each method. The methods were applied on the whole pelvis and on smaller fragments, thus producing a realistic set of clinical scenarios. Clinically relevant criteria are used for the assessment such as surface distances and the quality of the junctions between the donor and the receptor. The obtained results showed that both automatic methods outperform the manual counterpart. Additional advantages of the surface-based method are in the lower computational time requirements and the greater contact surfaces where the donor meets the recipien

    Financial stability challenges in candidate countries - managing the transition to deeper and more market-oriented financial systems.

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    This paper reviews financial stability challenges in the EU candidate countries Croatia, Turkey and the former Yugoslav Republic of Macedonia. It examines the fi nancial sectors in these three economies, which, while at very different stages of development and embedded in quite diverse economic settings, are all in a process of rapid financial deepening. This manifests itself most clearly in the rapid pace of growth in credit to the private sector. This process of financial deepening is largely a natural and welcome catching-up phenomenon, but it has also increased the credit risks borne by the banking sectors in the three economies. These credit risks are compounded by the widespread use of foreign currency-denominated or -indexed loans, leaving unhedged bank customers exposed to potential swings in exchange rates or foreign interest rates. Moreover, these financial risks form part of a broader nexus of vulnerabilities in the economies concerned, in particular the external vulnerabilities arising from increasing private sector external indebtedness. That said, the paper also fi nds that the authorities in the three countries have taken several policy actions to reduce these fi nancial and external vulnerabilities and to strengthen the resilience of the financial sectors. JEL Classification: F32, F41, G21, G28.Europe, banking sector, vulnerability indicators, capital inflows, emerging markets.

    Spread Divergences

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    For distributions p and q with different supports, the divergence D(p|q) may not exist. We define a spread divergence on modified p and q and describe sufficient conditions for the existence of such a divergence. We demonstrate how to maximize the discriminatory power of a given divergence by parameterizing and learning the spread. We also give examples of using a spread divergence to train and improve implicit generative models, including linear models (Independent Components Analysis) and non-linear models (Deep Generative Networks)

    Fast and powerful heritability inference for family-based neuroimaging studies.

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    Heritability estimation has become an important tool for imaging genetics studies. The large number of voxel- and vertex-wise measurements in imaging genetics studies presents a challenge both in terms of computational intensity and the need to account for elevated false positive risk because of the multiple testing problem. There is a gap in existing tools, as standard neuroimaging software cannot estimate heritability, and yet standard quantitative genetics tools cannot provide essential neuroimaging inferences, like family-wise error corrected voxel-wise or cluster-wise P-values. Moreover, available heritability tools rely on P-values that can be inaccurate with usual parametric inference methods. In this work we develop fast estimation and inference procedures for voxel-wise heritability, drawing on recent methodological results that simplify heritability likelihood computations (Blangero et al., 2013). We review the family of score and Wald tests and propose novel inference methods based on explained sum of squares of an auxiliary linear model. To address problems with inaccuracies with the standard results used to find P-values, we propose four different permutation schemes to allow semi-parametric inference (parametric likelihood-based estimation, non-parametric sampling distribution). In total, we evaluate 5 different significance tests for heritability, with either asymptotic parametric or permutation-based P-value computations. We identify a number of tests that are both computationally efficient and powerful, making them ideal candidates for heritability studies in the massive data setting. We illustrate our method on fractional anisotropy measures in 859 subjects from the Genetics of Brain Structure study
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