Ship-hull shape optimization with a T-spline based BEM-isogeometric solver

In this work, we present a ship-hull optimization process combining a T-spline based parametric ship-hull model and an Isogeometric Analysis (IGA) hydrodynamic solver for the calculation of ship wave resistance. The surface representation of the ship-hull instances comprise one cubic T-spline with extraordinary points, ensuring C2 continuity everywhere except for the vicinity of extraordinary points where G1 continuity is achieved. The employed solver for ship wave resistance is based on the Neumann-Kelvin formulation of the problem, where the resulting Boundary Integral Equation is numerically solved using a higher order collocated Boundary Element Method which adopts the IGA concept and the T-spline representation for the ship-hull surface. The hydrodynamic solver along with the ship parametric model are subsequently integrated within an appropriate optimization environment for local and global ship-hull optimizations against the criterion of minimum resistance

VerdictDB: Universalizing Approximate Query Processing

Despite 25 years of research in academia, approximate query processing (AQP) has had little industrial adoption. One of the major causes of this slow adoption is the reluctance of traditional vendors to make radical changes to their legacy codebases, and the preoccupation of newer vendors (e.g., SQL-on-Hadoop products) with implementing standard features. Additionally, the few AQP engines that are available are each tied to a specific platform and require users to completely abandon their existing databases---an unrealistic expectation given the infancy of the AQP technology. Therefore, we argue that a universal solution is needed: a database-agnostic approximation engine that will widen the reach of this emerging technology across various platforms. Our proposal, called VerdictDB, uses a middleware architecture that requires no changes to the backend database, and thus, can work with all off-the-shelf engines. Operating at the driver-level, VerdictDB intercepts analytical queries issued to the database and rewrites them into another query that, if executed by any standard relational engine, will yield sufficient information for computing an approximate answer. VerdictDB uses the returned result set to compute an approximate answer and error estimates, which are then passed on to the user or application. However, lack of access to the query execution layer introduces significant challenges in terms of generality, correctness, and efficiency. This paper shows how VerdictDB overcomes these challenges and delivers up to 171$\times$ speedup (18.45$\times$ on average) for a variety of existing engines, such as Impala, Spark SQL, and Amazon Redshift, while incurring less than 2.6% relative error. VerdictDB is open-sourced under Apache License.Comment: Extended technical report of the paper that appeared in Proceedings of the 2018 International Conference on Management of Data, pp. 1461-1476. ACM, 201

Inconsistency of the MLE for the joint distribution of interval censored survival times and continuous marks

This paper considers the nonparametric maximum likelihood estimator (MLE) for the joint distribution function of an interval censored survival time and a continuous mark variable. We provide a new explicit formula for the MLE in this problem. We use this formula and the mark specific cumulative hazard function of Huang and Louis (1998) to obtain the almost sure limit of the MLE. This result leads to necessary and sufficient conditions for consistency of the MLE which imply that the MLE is inconsistent in general. We show that the inconsistency can be repaired by discretizing the marks. Our theoretical results are supported by simulations.Comment: 27 pages, 4 figure

Prox1 Regulates the Notch1-Mediated Inhibition of Neurogenesis

During development of the spinal cord, Prox1 controls the balance between proliferation and differentiation of neural progenitor cells via suppression of Notch1 gene expression

Clinical application of stem cell therapy in Parkinson's disease

Cell replacement therapies in Parkinson's disease (PD) aim to provide long-lasting relief of patients' symptoms. Previous clinical trials using transplantation of human fetal ventral mesencephalic (hfVM) tissue in the striata of PD patients have provided proof-of-principle that such grafts can restore striatal dopaminergic (DA-ergic) function. The transplants survive, reinnervate the striatum, and generate adequate symptomatic relief in some patients for more than a decade following operation. However, the initial clinical trials lacked homogeneity of outcomes and were hindered by the development of troublesome graft-induced dyskinesias in a subgroup of patients. Although recent knowledge has provided insights for overcoming these obstacles, it is unlikely that transplantation of hfVM tissue will become routine treatment for PD owing to problems with tissue availability and standardization of the grafts. The main focus now is on producing DA-ergic neuroblasts for transplantation from stem cells (SCs). There is a range of emerging sources of SCs for generating a DA-ergic fate in vitro. However, the translation of these efforts in vivo currently lacks efficacy and sustainability. A successful, clinically competitive SC therapy in PD needs to produce long-lasting symptomatic relief without side effects while counteracting PD progression

Pterional variable topography and morphology. An anatomical study and its clinical significance

Background: Pterion is the junction of the frontal, parietal, greater wing of the sphenoid and the squamous part of the temporal bone. The sphenoparietal, frontotemporal, stellate and epipteric pteria were described. The current study determines pterion topography, morphology (variant types’ frequency) and morphometry, as well as epipteric bones presence in dried skulls. Gender impact is underlined as well. Material and methods: Ninety Greek adult dried skulls were observed. The distances in between pterion and the zygomatic arch midpoint and in between pterion and the frontozygomatic suture were measured. Results: The sphenoparietal pterion was the commonest (58.3%), following by the stellate (25%), epipteric (15.5%) and by the frontotemporal pterion (1.1%). Twenty-eight skulls (15.5%) had epipteric bones, further categorized as quadrisutural (35.7%), trisutural (57.1%), bisutural and multiple (3.57%). The mean distances between pterion and the midpoint of zygomatic arch were 4.13+0.45cm on the right and 4.09 + 0.47cm on the left side and between pterion and the frontozygomatic suture were 3.47 + 0.61 cm on the right and 3.52 + 0.65 cm on the left. Both distances were symmetrical. Male skulls showed slightly higher values on the left side for the distance pterion and midpoint of zygomatic arch. Conclusions: Pterion is a commonly used neurosurgical landmark and thus in depth knowledge of the pteric area and its variants could be valuable. Recognition of the possible variability in pterion location, morphology and morphometry, as well as possible occurrence of epipteric bones may render pterional craniotomy safer among different population groups

Characterization of 3 PET Tracers for Quantification of Mitochondrial and Synaptic Function in Healthy Human Brain: {18}^F-BCPP-EF, {11}^C-SA-4503, and {11}^C-UCB-J

Mitochondrial complex 1 is involved in maintaining brain bioenergetics; σ-1 receptor responds to neuronal stress; and synaptic vesicle protein 2A reflects synaptic integrity. Expression of each of these proteins is altered in neurodegenerative diseases. Here, we characterize the kinetic behavior of 3 PET radioligands—{18}^F-BCPP-EF, {11}^C-SA-4503, and {11}^C-UCB-J for the measurement of mitochondrial complex 1, σ-1 receptor, and synaptic vesicle protein 2A, respectively, and determine appropriate analysis workflows for their application in future studies of the in vivo molecular pathology of these diseases. METHODS: Twelve human subjects underwent dynamic PET scans with each radioligand, including associated arterial blood sampling. A range of kinetic models was investigated to identify an optimal kinetic analysis method for each radioligand and a suitable acquisition duration. RESULTS: All 3 radioligands readily entered the brain and yielded heterogeneous uptake consistent with the known distribution of the targets. The optimal models determined for the regional estimates of volume of distribution were multilinear analysis 1 (MA1) and the 2-tissue-compartment model for {18}^F-BCPP-EF, MA1 for 11}^C-SA-4503, and both MA1 and the 1-tissue-compartment model for {11}^C-UCB-J, respectively, provided good estimates of regional volume of distribution values. An effect of age was observed on {18}^F-BCPP-EF and {11}^C-UCB-J signal in the caudate. CONCLUSION: These ligands can be assessed for their potential to stratify patients or monitor the progression of molecular neuropathology in neurodegenerative diseases