Comparison of state-of-the-art neural network survival models with the Pooled Cohort Equations for cardiovascular disease risk prediction

BACKGROUND: The Pooled Cohort Equations (PCEs) are race- and sex-specific Cox proportional hazards (PH)-based models used for 10-year atherosclerotic cardiovascular disease (ASCVD) risk prediction with acceptable discrimination. In recent years, neural network models have gained increasing popularity with their success in image recognition and text classification. Various survival neural network models have been proposed by combining survival analysis and neural network architecture to take advantage of the strengths from both. However, the performance of these survival neural network models compared to each other and to PCEs in ASCVD prediction is unknown. METHODS: In this study, we used 6 cohorts from the Lifetime Risk Pooling Project (with 5 cohorts as training/internal validation and one cohort as external validation) and compared the performance of the PCEs in 10-year ASCVD risk prediction with an all two-way interactions Cox PH model (Cox PH-TWI) and three state-of-the-art neural network survival models including Nnet-survival, Deepsurv, and Cox-nnet. For all the models, we used the same 7 covariates as used in the PCEs. We fitted each of the aforementioned models in white females, white males, black females, and black males, respectively. We evaluated models\u27 internal and external discrimination power and calibration. RESULTS: The training/internal validation sample comprised 23216 individuals. The average age at baseline was 57.8 years old (SD = 9.6); 16% developed ASCVD during average follow-up of 10.50 (SD = 3.02) years. Based on 10 × 10 cross-validation, the method that had the highest C-statistics was Deepsurv (0.7371) for white males, Deepsurv and Cox PH-TWI (0.7972) for white females, PCE (0.6981) for black males, and Deepsurv (0.7886) for black females. In the external validation dataset, Deepsurv (0.7032), Cox-nnet (0.7282), PCE (0.6811), and Deepsurv (0.7316) had the highest C-statistics for white male, white female, black male, and black female population, respectively. Calibration plots showed that in 10 × 10 validation, all models had good calibration in all race and sex groups. In external validation, all models overestimated the risk for 10-year ASCVD. CONCLUSIONS: We demonstrated the use of the state-of-the-art neural network survival models in ASCVD risk prediction. Neural network survival models had similar if not superior discrimination and calibration compared to PCEs

Identification of PLXDC1 and PLXDC2 as the transmembrane receptors for the multifunctional factor PEDF.

Pigment Epithelium Derived Factor (PEDF) is a secreted factor that has broad biological activities. It was first identified as a neurotrophic factor and later as the most potent natural antiangiogenic factor, a stem cell niche factor, and an inhibitor of cancer cell growth. Numerous animal models demonstrated its therapeutic value in treating blinding diseases and diverse cancer types. A long-standing challenge is to reveal how PEDF acts on its target cells and the identities of the cell-surface receptors responsible for its activities. Here we report the identification of transmembrane proteins PLXDC1 and PLXDC2 as cell-surface receptors for PEDF. Using distinct cellular models, we demonstrate their cell type-specific receptor activities through loss of function and gain of function studies. Our experiments suggest that PEDF receptors form homooligomers under basal conditions, and PEDF dissociates the homooligomer to activate the receptors. Mutations in the intracellular domain can have profound effects on receptor activities

Enhancing secrecy rate in cognitive radio networks via stackelberg game

In this paper, a game theory based cooperation scheme is investigated to enhance the physical layer security in both primary and secondary transmissions of a cognitive radio network (CRN). In CRNs, the primary network may decide to lease its own spectrum for a fraction of time to the secondary nodes in exchange of appropriate remuneration. We consider the secondary transmitter node as a trusted relay for primary transmission to forward primary messages in a decode-and-forward (DF) fashion and, at the same time, allows part of its available power to be used to transmit artificial noise (i.e., jamming signal) to enhance primary and secondary secrecy rates. In order to allocate power between message and jamming signals, we formulate and solve the optimization problem for maximizing the secrecy rates under malicious attempts from EDs. We then analyse the cooperation between the primary and secondary nodes from a game-theoretic perspective where we model their interaction as a Stackelberg game with a theoretically proved and computed Stackelberg equilibrium. We show that the spectrum leasing based on trading secondary access for cooperation by means of relay and jammer is a promising framework for enhancing security in CRNs

Enhancing secrecy rate in cognitive radio networks via multilevel Stackelberg game

In this letter, physical layer (PHY) security is investigated for both primary and secondary transmissions of a cognitive radio network (CRN) that is in danger of malicious attempt by an eavesdropper (ED). In our proposed system, the secondary transmitter (ST) is acted as a trusted relay (TR) for primary transmission and the PHY security is facilitated by the cooperation between the primary transmitter (PT) and the ST using the multilevel Stackelberg game. In particular, we formulate and solve the optimization problem of maximizing secrecy rates in different phases of primary and secondary transmissions. Finally, numerical examples are provided to demonstrate that the spectrum leasing based on trading secondary access for cooperation is a promising framework for enhancing secrecy rate in CRNs

Centrifuge modeling of rocking-isolated inelastic RC bridge piers

Experimental proof is provided of an unconventional seismic design concept, which is based on deliberately underdesigning shallow foundations to promote intense rocking oscillations and thereby to dramatically improve the seismic resilience of structures. Termed rocking isolation, this new seismic design philosophy is investigated through a series of dynamic centrifuge experiments on properly scaled models of a modern reinforced concrete (RC) bridge pier. The experimental method reproduces the nonlinear and inelastic response of both the soil-footing interface and the structure. To this end, a novel scale model RC (1:50 scale) that simulates reasonably well the elastic response and the failure of prototype RC elements is utilized, along with realistic representation of the soil behavior in a geotechnical centrifuge. A variety of seismic ground motions are considered as excitations. They result in consistent demonstrably beneficial performance of the rocking-isolated pier in comparison with the one designed conventionally. Seismic demand is reduced in terms of both inertial load and deck drift. Furthermore, foundation uplifting has a self-centering potential, whereas soil yielding is shown to provide a particularly effective energy dissipation mechanism, exhibiting significant resistance to cumulative damage. Thanks to such mechanisms, the rocking pier survived, with no signs of structural distress, a deleterious sequence of seismic motions that caused collapse of the conventionally designed pier. © 2014 The Authors Earthquake Engineering & Structural Dynamics Published by John Wiley & Sons Ltd

Deformation and mechanical properties of the expansive cements produced by inter-grinding cement clinker and MgOs with various reactivities

Magnesia (MgO) either intrinsically contained in cement clinker or prepared separately as expansive additive has been used to compensate for the shrinkage of cementitious materials. In this study, for improving the homogenous distribution of MgOs, the cement clinker was inter-ground with MgO expansive additives with various reactivities ranging from 50 to 400 s to prepare series of expansive Portland cements and blended cements with incorporation of slag and fly ash. The deformations and mechanical properties of the expansive cements were investigated. Results showed that the expansive cements containing more reactive MgOs produced more rapid expansion under sealed condition or water curing, leading to effective autogenous shrinkage compensations at early age. The reactivities of MgOs caused insignificant influences on the mechanical strengths of expansive cements. The blended cements had lower strengths at early age but higher strengths than that of the corresponding Portland cements at late age due to the pozzolanic reaction.The financial support from the Royal Academy of Engineering UK/China, India Exchange, The National Key Technology R&D Program (2011BAE27B01-1), Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and National Natural Science Foundation of China (51461135003) are acknowledged.This is the accepted manuscript. The final version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0950061815000914#

Enhancing secrecy rate in cognitive radio networks via multilevel Stackelberg game

In this letter, physical layer (PHY) security is investigated for both primary and secondary transmissions of a cognitive radio network (CRN) that is in danger of malicious attempt by an eavesdropper (ED). In our proposed system, the secondary transmitter (ST) is acted as a trusted relay (TR) for primary transmission and the PHY security is facilitated by the cooperation between the primary transmitter (PT) and the ST using the multilevel Stackelberg game. In particular, we formulate and solve the optimization problem of maximizing secrecy rates in different phases of primary and secondary transmissions. Finally, numerical examples are provided to demonstrate that the spectrum leasing based on trading secondary access for cooperation is a promising framework for enhancing secrecy rate in CRNs

Enhancing secrecy rate in cognitive radio networks via stackelberg game

In this paper, a game theory based cooperation scheme is investigated to enhance the physical layer security in both primary and secondary transmissions of a cognitive radio network (CRN). In CRNs, the primary network may decide to lease its own spectrum for a fraction of time to the secondary nodes in exchange of appropriate remuneration. We consider the secondary transmitter node as a trusted relay for primary transmission to forward primary messages in a decode-and-forward (DF) fashion and, at the same time, allows part of its available power to be used to transmit artificial noise (i.e., jamming signal) to enhance primary and secondary secrecy rates. In order to allocate power between message and jamming signals, we formulate and solve the optimization problem for maximizing the secrecy rates under malicious attempts from EDs. We then analyse the cooperation between the primary and secondary nodes from a game-theoretic perspective where we model their interaction as a Stackelberg game with a theoretically proved and computed Stackelberg equilibrium. We show that the spectrum leasing based on trading secondary access for cooperation by means of relay and jammer is a promising framework for enhancing security in CRNs

Full-duplex small cells for next generation heterogeneous cellular networks: a case study of outage and rate coverage analysis.

Full-duplex (FD) technology is currently under consideration for adoption in a range of legacy communications standards due to its attractive features. On the other hand, cellular networks are becoming increasingly heterogeneous as operators deploy a mix of macrocells and small cells. With growing tendency toward network densification, small cells are expected to play a key role in realizing the envisioned capacity objectives of emerging 5G cellular networks. From a practical perspective, small cells provide an ideal platform for deploying FD technology in cellular networks due to its lower transmit power and lower cost for implementation compared with the macrocell counterpart. Motivated by these developments, in this paper, we analyze a two-Tier heterogeneous cellular network, wherein the first tier comprises half-duplex macrobase stations and the second tier consists of the FD small cells. Through a stochastic geometry approach, we characterize and derive the closed-form expressions for the outage probability and the rate coverage. Our analysis explicitly accounts for the spatial density, the self-interference cancellation capabilities, and the interference coordination based on enhanced inter-cell interference coordination techniques. Performance evaluation investigates the impact of different parameters on the outage probability and the rate coverage in various scenarios

Deformation and mechanical properties of quaternary blended cements containing ground granulated blast furnace slag, fly ash and magnesia

Shrinkages of cementitious materials may lead to cracking under restrained conditions. This study was motivated to develop non-shrinkage quaternary blended cements through blending slag and fly ash with Portland cement containing reactive MgO. The hydration process, autogenous shrinkage at early age, long-term volume deformation, mechanical properties, and microstructure of cement specimens were investigated. Results showed that the autogenous shrinkage of the cement pastes was effectively mitigated due to the compensation of the MgO present and the reduction of cement content owing to the partial replacements with slag and fly ash. The mechanical strengths of the blended cement mortars were lower than that of the corresponding plain Portland cement mortars at early age of 3 d, but increased significantly to be similar or higher at late ages of 28 d and 90 d. This is attributed to the microstructure densification and the interface microstructure enhancement due to the reaction of SCMs with clinker phases.The financial support from the Royal Academy of Engineering UK/China Exchange (12/13RECI013), the National Key Technology R&D Program (2011BAE27B01-1), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and the National Natural Science Foundation of China (51461135003) is acknowledged.This is the accepted manuscript. The final published version is available from Elsevier at http://www.sciencedirect.com/science/article/pii/S0008884615000319