Browsing by Author "Wang, X."
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Item A Bayesian Latent Variable Approach to Aggregation of Partial and Top-Ranked Lists in Genomic Studies(Wiley) Li, X.; Choudhary, Pankaj K.; Biswas, Swati; Wang, X.; 0000 0001 2704 188X (Biswas, S); 0000-0002-0398-7459 (Choudary, PK); Choudhary, Pankaj K.; Biswas, SwatiIn genomic research, it is becoming increasingly popular to perform meta-analysis, the practice of combining results from multiple studies that target a common essential biological problem. Rank aggregation, a robust meta-analytic approach, consolidates such studies at the rank level. There exists extensive research on this topic, and various methods have been developed in the past. However, these methods have two major limitations when they are applied in the genomic context. First, they are mainly designed to work with full lists, whereas partial and/or top-ranked lists prevail in genomic studies. Second, the component studies are often clustered, and the existing methods fail to utilize such information. To address the above concerns, a Bayesian latent variable approach, called BiG, is proposed to formally deal with partial and top-ranked lists and incorporate the effect of clustering. Various reasonable prior specifications for variance parameters in hierarchical models are carefully studied and compared. Simulation results demonstrate the superior performance of BiG compared with other popular rank aggregation methods under various practical settings. A non–small-cell lung cancer data example is analyzed for illustration.Item A Multiscale Model to Study the Enhancement in the Compressive Strength of Multi-Walled CNT Sheet Overwrapped Carbon Fiber Composites(Elsevier Ltd) Ravindranath, P. K.; Roy, S.; Unnikrishnan, V.; Wang, X.; Xu, Tingge; Baughman, Ray H.; Lu, Hongbing; 0000-0001-5845-5137 (Baughman, RH); Xu, Tingge; Baughman, Ray H.; Lu, HongbingThe high tensile strength of polymer matrix composites is derived primarily from the high strength of the carbon fibers embedded in the polymer matrix. However, their compressive strength is generally much lower due to the fact that under compression, the fibers tend to fail through micro-buckling well before compressive fracture occurs. In this work, we consider multi-walled carbon nanotube (MWNT) sheets wrapped around carbon fiber at room temperature to improve fiber/matrix interfacial properties which, in turn, influences compressive strength of the composite. To investigate the effect of the wrapping of MWNT sheet on composite strength, Molecular Dynamics simulations were performed on an atomistic model of the interface region between the epoxy, carbon fiber and the scrolled MWNT sheets. The compressive strength of the unidirectional composite was computed using a novel hierarchical multi-scale model comprising of the rule of mixtures at the microscale, and the modified Argon's formula for composites at the macroscale. Model predictions were benchmarked through comparison with experimental data for different volume fractions of MWNT sheet. ©2019 Elsevier LtdItem Blue Light Emitting Electrochemical Cells Incorporating Triazole-based Luminophores(2013-09-20) Fernández-Hernández, Jesús M.; Ladouceur, S.; Shen, Y.; Iordache, A.; Wang, X.; Donato, L.; Gallagher-Duval, S.; de Anda Villa, Manuel; Slinker, Jason D.; De Cola, L.; Zysman-Colman, E.; 0000 0001 2791 9795 (Slinker, JD); Slinker, Jason D.We report the electrochemical, photoluminescence, and electroluminescence properties of four fluorinated cationic iridium complexes bearing pyridyltriazole ancillary ligands. All the complexes display unstructured emission in the true blue region at 298 K with photoluminescent λem ranging from 452 to 487 nm in acetonitrile solution, in powder and in PMMA doped thin films. The nature of the emission is a mixed metal-to-ligand/ligand-to-ligand charge transfer state. Photoluminescence (PL) quantum efficiencies both in solution and in the solid state were low while excited state decay kinetics were found to be multiexponential. Each complex undergoes quasi-reversible oxidation and irreversible reduction with large HOMO-LUMO gaps. A detailed computational investigation corroborates the spectroscopic assignments. Additionally, light-emitting electrochemical cells (LEECs) were fabricated for each of the four complexes. The electroluminescence (EL) spectra of all complexes were red-shifted relative to the PL spectra. The LEEC containing 2a is the bluest emitter (λmax = 487 nm) of the family of complexes.Item Enhanced Thermal Conductivity in Cu/Diamond Composites by Tailoring the Thickness of Interfacial TiC Layer(Elsevier Ltd) Wang, Luhua; Li, J.; Catalano, Massimo; Bai, G.; Li, N.; Dai, J.; Wang, X.; Zhang, H.; Wang, Jinguo; Kim, Moon J.; Wang, Luhua; Catalano, Massimo; Wang, Jinguo; Kim, Moon J.Diamond particles reinforced Cu matrix (Cu/diamond) composites were fabricated by gas pressure infiltration using Ti-coated diamond particles with Ti coating from 65 nm to 850 nm. The scanning transmission electron microscopy (STEM) characterizes that the Ti coating transforms from elemental Ti to TiC after infiltration, and the crystallographic orientation relationship between diamond and TiC is [1 1 0]_{diamond}//[1 1 0]_{TiC} and (1 1 1)_{diamond}//(1 1 1)_{TiC}. The thermal conductivity of the Cu/Ti-diamond composites firstly increases and then decreases with increasing Ti coating thickness, giving a maximal value of 811 W m⁻¹ K⁻¹ at 220 nm Ti-coating layer. The results clearly manifest the effect of interfacial layer thickness on the thermal conductivity of Cu/diamond composites.Item FOGPLAN: A Lightweight QoS-Aware Dynamic Fog Service Provisioning Framework(Institute of Electrical and Electronics Engineers Inc., 2019-01-30) Yousefpour, Ashkan; Patil, Ashish; Ishigaki, Genya; Kim, I.; Wang, X.; Cankaya, H. C.; Zhang, Q.; Xie, W.; Jue, Jason P.; 0000-0003-4869-9183 (Yousefpour, A); 0000-0003-3655-7532 (Ishigaki, G); Yousefpour, Ashkan; Patil, Ashish; Ishigaki, Genya; Jue, Jason P.Recent advances in the areas of Internet of Things (IoT), big data, and machine learning have contributed to the rise of a growing number of complex applications. These applications will be data-intensive, delay-sensitive, and real-time as smart devices prevail more in our daily life. Ensuring quality of service (QoS) for delay-sensitive applications is a must, and fog computing is seen as one of the primary enablers for satisfying such tight QoS requirements, as it puts compute, storage, and networking resources closer to the user. In this paper, we first introduce FOGPLAN, a framework for QoS-aware dynamic fog service provisioning (QDFSP). QDFSP concerns the dynamic deployment of application services on fog nodes, or the release of application services that have previously been deployed on fog nodes, in order to meet low latency and QoS requirements of applications while minimizing cost. FOGPLAN framework is practical and operates with no assumptions and minimal information about IoT nodes. Next, we present a possible formulation (as an optimization problem) and two efficient greedy algorithms for addressing the QDFSP at one instance of time. Finally, the FOGPLAN framework is evaluated using a simulation based on real-world traffic traces. © 2019 IEEE.Item Frequency Offset Corrected Inversion Pulse for B₀ and B₁ Insensitive Fat Suppression at 3T: Application to MR Neurography of Brachial Plexus(John Wiley and Sons Inc.) Wang, X.; Greer, Joshua S.; Dimitrov, I. E.; Pezeshk, P.; Chhabra, A.; Madhuranthakam, A. J.; Greer, Joshua S.BACKGROUND: The 3D short tau inversion recovery (STIR) sequence is routinely used in clinical MRI to achieve robust fat suppression. However, the performance of the commonly used adiabatic inversion pulse, hyperbolic secant (HS), is compromised in challenging areas with increased B₀ and B₁ inhomogeneities, such as brachial plexus at 3T. PURPOSE: To demonstrate the frequency offset corrected inversion (FOCI) pulse as an efficient fat suppression STIR pulse with increased robustness to B₀ and B₁ inhomogeneities at 3T, compared to the HS pulse. STUDY TYPE: Prospective. SUBJECTS/PHANTOM: Initial evaluation was performed in phantoms and one healthy volunteer by varying the B₁ field, while subsequent comparison was performed in three healthy volunteers and five patients without varying the B₁. FIELD STRENGTH/SEQUENCE: 3T; 3D TSE-STIR with HS and FOCI pulses. ASSESSMENT: Brachial plexus images were qualitatively evaluated by two musculoskeletal radiologists independently using a four-point grading scale for fat suppression, shading artifacts, and nerve visualization. STATISTICAL TEST: The Wilcoxon signed-rank test with P < 0.05 was considered statistically significant. RESULTS: Simulations and phantom experiments demonstrated broader bandwidth (2.5 kHz vs. 0.83 kHz, increased B₀ robustness) at the same adiabatic threshold and lower adiabatic threshold (5 μT vs. 7 μT at 3.5 ppm, increased B₁ robustness) at the same bandwidth with the FOCI pulse compared to the HS pulse. With increased bandwidth, the FOCI pulse achieved robust fat suppression even at 50% of maximum B₁ strength, while the HS pulse required > 75% of maximum B₁ strength. Compared to the standard 3D TSE-STIR with HS pulse, the FOCI pulse achieved uniform fat suppression (P < 0.05), better nerve visualization (P < 0.05), and minimal shading artifacts (P < 0.01) in brachial plexus at 3T. DATA CONCLUSION: The FOCI pulse has increased robustness to B₀ and B₁ inhomogeneities, compared to the HS LEVEL OF EVIDENCE: 1. TECHNICAL EFFICACY: Stage 1.Item Guaranteed-Availability Network Function Virtualization in Inter-Datacenter Networks(Institute of Electrical and Electronics Engineers Inc.) Kong, Jian; Kim, I.; Wang, X.; Zhang, Q.; Xie, W.; Cankaya, H. C.; Wang, N.; Ikeuchi, T.; Jue, Jason P.; Kong, Jian; Jue, Jason P.Considering the availability of the datacenter's network elements, we propose a coordinated protection mechanism that adopts both backup path protection and SFC replicas distributed among datacenters to support high availability while reducing total cost.Item High Thermal Conductivity in Cubic Boron Arsenide Crystals(American Association for the Advancement of Science) Li, Sheng; Zheng, Q.; Lv, Y.; Liu, Xiaoyuan; Wang, X.; Huang, P. Y.; Cahill, D. G.; Lv, Bing; Li, Sheng; Liu, Xiaoyuan; Lv, BingThe high density of heat generated in power electronics and optoelectronic devices is a critical bottleneck in their application. New, high thermally-conducting materials are needed to effectively dissipate heat and thereby enable enhanced performance of power controls, solid-state lighting, communication, and security systems. We report our experimental discovery of high thermal conductivity of 1000 ± 90 W/m/K at room temperature in cubic boron arsenide (BAs) grown through modified chemical vapor transport technique. Such thermal conductivity is a factor of 3 higher than that of silicon carbide and surpassed only by diamond and the basal plane value of graphite. This work establishes BAs as the first realization of a new class of ultrahigh thermal conductivity materials predicted by a recent theory, and a potential revolutionary thermal management material.Item Identifying CDKN3 Gene Expression as a Prognostic Biomarker in Lung Adenocarcinoma via Meta-Analysis(Libertas Academica Ltd., 2015-03-24) Zang, X.; Chen, Min; Zhou, Y.; Xiao, G.; Xie, Y.; Wang, X.Lung cancer is among the major causes of cancer deaths, and the survival rate of lung cancer patients is extremely low. Recent studies have demonstrated that the gene CDKN3 is related to neoplasia, but in the literature severe controversy exists over whether it is involved in cancer progression or, conversely, tumor inhibition. In this study, we investigated the expression of CDKN3 and its association with prognosis in lung adenocarcinoma (ADC) and squamous cell carcinoma (SCC) using datasets in Lung Cancer Explorer (LCE; http://qbrc.swmed.edu/lce/). We found that CDKN3 was up-regulated in ADC and SCC compared to normal tissues. We also found that CDKN3 was expressed at a higher level in SCC than in ADC, which was further validated through meta-analysis (coefficient = 2.09, 95% CI = 1.50–2.67, P < 0.0001). In addition, based on meta-analysis for the prognostic value of CDKN3, we found that higher CDKN3 expression was associated with poorer survival outcomes in ADC (HR = 1.65, 95% CI = 1.39–1.96, P < 0.0001), but not in SCC (HR = 1.10, 95% CI = 0.84–1.44, P = 0.494). Our findings indicate that CDKN3 may be a prognostic marker in ADC, though the detailed mechanism is yet to be revealed.Item Nucleosome Eviction and Multiple Co-Factor Binding Predict Estrogen-Receptor-Alpha-Asociated Long-Range Interactions(Oxford University Press, 2014-04-29) He, C.; Wang, X.; Zhang, Michael Q.; 0000 0001 1707 1372 (Zhang, MQ); 99086074 (Zhang, MQ); Zhang, Michael Q.Many enhancers regulate their target genes via long-distance interactions. High-throughput experiments like ChIA-PET have been developed to map such largely cell-type-specific interactions between cis-regulatory elements genome-widely. In this study, we integrated multiple types of data in order to reveal the general hidden patterns embedded in the ChIA-PET data. We found characteristic distance features related to promoter-promoter, enhancer-enhancer and insulator-insulator interactions. Although a protein may have many binding sites along the genome, our hypothesis is that those sites that share certain open chromatin structure can accommodate relatively larger protein complex consisting of specific regulatory and 'bridging' factors, and may be more likely to form robust long-range deoxyribonucleic acid (DNA) loops. This hypothesis was validated in the estrogen receptor alpha (ERa) ChIA-PET data. An efficient classifier was built to predict ERa-associated long-range interactions solely from the related ChIP-seq data, hence linking distal ERa-dependent enhancers to their target genes. We further applied the classifier to generate additional novel interactions, which were undetected in the original ChIA-PET paper but were validated by other independent experiments. Our work provides a new insight into the long-range chromatin interactions through deeper and integrative ChIA-PET data analysis and demonstrates DNA looping predictability from ordinary ChIP-seq data.Item Optical Biopsy of Head and Neck Cancer Using Hyperspectral Imaging and Convolutional Neural Networks(SPIE) Halicek, Martin; Little, J. V.; Wang, X.; Chen, A. Y.; Fei, Baowei; 0000-0002-9123-9484 (Fei, B); Halicek, Martin; Fei, BaoweiFor patients undergoing surgical cancer resection of squamous cell carcinoma (SCCa), cancer-free surgical margins are essential for good prognosis. We developed a method to use hyperspectral imaging (HSI), a noncontact optical imaging modality, and convolutional neural networks (CNNs) to perform an optical biopsy of ex-vivo, surgical gross-tissue specimens, collected from 21 patients undergoing surgical cancer resection. Using a cross-validation paradigm with data from different patients, the CNN can distinguish SCCa from normal aerodigestive tract tissues with an area under the receiver operator curve (AUC) of 0.82. Additionally, normal tissue from the upper aerodigestive tract can be subclassified into squamous epithelium, muscle, and gland with an average AUC of 0.94. After separately training on thyroid tissue, the CNN can differentiate between thyroid carcinoma and normal thyroid with an AUC of 0.95, 92% accuracy, 92% sensitivity, and 92% specificity. Moreover, the CNN can discriminate medullary thyroid carcinoma from benign multinodular goiter (MNG) with an AUC of 0.93. Classical-type papillary thyroid carcinoma is differentiated from MNG with an AUC of 0.91. Our preliminary results demonstrate that an HSI-based optical biopsy method using CNNs can provide multicategory diagnostic information for normal and cancerous head-and-neck tissue, and more patient data are needed to fully investigate the potential and reliability of the proposed technique. ©2019 The AuthorsItem Tailoring Interface Structure and Enhancing Thermal Conductivity of Cu/Diamond Composites by Alloying Boron to the Cu Matrix(Elsevier Inc.) Bai, G.; Wang, Luhua; Zhang, Y.; Wang, X.; Wang, Jinguo; Kim, Moon J.; Zhang, H.; Wang, Luhua; Wang, Jinguo; Kim, Moon J.Diamond particles reinforced Cu matrix (Cu/diamond) composites were prepared by alloying 0.1–1.0 wt% B to the Cu matrix in order to tailor the interface structure. The interface structure evolves from discrete triangular carbides into continuous jig-saw carbides depending on the availability of boron source in the Cu-B matrix. We report the highest thermal conductivity of 868 W/mK so far in boron-modified Cu/diamond composites, which originates from the discontinuous carbide interface in the Cu-B/diamond composites. The parallel connection of interfacial thermal resistances of the discontinuous carbide interface reduces the total interfacial thermal resistance and therefore promotes phonon transfer across the Cu/diamond interface. We clarify the formation mechanism of discontinuous carbide interface in the Cu-B/diamond composites and demonstrate the decisive role of discrete triangular carbides in enhancing thermal conductivity of Cu/diamond composites. The results help to establish the method of metal matrix alloying to prepare Cu/diamond composites with high thermal conductivity for thermal management applications. © 2019 Elsevier Inc.Item Tunable Coefficient of Thermal Expansion of Cu-B/Diamond Composites Prepared by Gas Pressure Infiltration(Elsevier Ltd) Bai, G.; Zhang, Y.; Dai, J.; Wang, L.; Wang, X.; Wang, Jinguo; Kim, Moon J.; Chen, X.; Zhang, H.; Wang, Jinguo; Kim, Moon J.Cu-B matrix composites reinforced with diamond particles (Cu-B/diamond) were prepared by gas pressure infiltration (GPI). The effect of boron addition in the range of 0–1.0 wt% on the thermal expansion behavior of the Cu-B/diamond composites was evaluated. The coefficient of thermal expansion (CTE) of the Cu-B/diamond composites initially decreases and then increases with increasing boron content. The minimum CTE value of 4.88 × 10 -6 /K is obtained at 0.5 wt% B addition, which satisfies the requirement of CTE of semiconductors (range of 4–8 × 10⁻⁶ /K) for electronic packaging applications. The variation of CTE of the Cu-B/diamond composites is attributed to the formation of interfacial carbides and their morphological evolution. The interface structure evolves from discrete triangular carbides into continuous carbide layer with increasing boron content. The increase in the quantity of discrete carbides enhances the interface, but the formation of continuous carbides impairs the interfacial bonding of the Cu-B/diamond composites. The results suggest that alloying B to Cu matrix is an effective route to tune the coefficient of thermal expansion of Cu/diamond composites. © 2019 Elsevier B.V.Item Two-Dimensional gcPIC Simulation of Rising-Tone Chorus Waves in a Dipole Magnetic Field(Blackwell Publishing Ltd, 2019-06-18) Lu, Q.; Ke, Y.; Wang, X.; Liu, K.; Gao, X.; Chen, Lunjin; Wang, S.; 0000-0003-2489-3571 (Chen, L); Chen, LunjinRising-tone chorus waves have already been successfully produced in a mirror magnetic field with the use of one- and two-dimensional particle-in-cell (PIC) simulations. However, in reality, the background magnetic field in the inner Earth's magnetosphere is a dipole magnetic field, unlike symmetric mirror fields. In this paper, with the two-dimensional (2-D) general curvilinear PIC (gcPIC) code, we investigate the generation of rising-tone chorus waves in the dipole magnetic field configuration. The plasma consists of three components: immobile ions, cold background, and hot electrons. In order to save computational resource, the topology of the magnetic field is roughly equal to that at L = 0.6 R_{E}, although the plasma parameters corresponding to those at L = 6 R_{E} (R_{E} is the Earth's radius) are used. Whistler mode waves are first excited around the magnetic equator by the hot electrons with a temperature anisotropy. The excited whistler mode waves propagate almost parallel and antiparallel to the background magnetic field in their source region, which is limited at ∣λ ∣ ≤ 3° (where λ is the magnetic latitude). When the waves leave from the source region and propagate toward high latitudes, both their amplitude and wave normal angle become larger. However, the group velocity of the waves is directed toward high latitudes almost along the magnetic field. During such a process, the waves have a frequency chirping, as shown by a rising tone in the frequency-time spectrogram. To our best knowledge, it is for the first time that rising-tone chorus are generated in a dipole magnetic field with a PIC simulation. ©2019. American Geophysical Union. All Rights Reserved.Item Two-Dimensional Particle-In-Cell Simulation of Magnetosonic Wave Excitation in a Dipole Magnetic Field(Blackwell Publishing Ltd) Chen, Lunjin; Sun, Jicheng; Lu, Q.; Wang, X.; Gao, X.; Wang, D.; Wang, S.; 0000-0002-5059-5394 (Sun, J); Chen, Lunjin; Sun, JichengThe excitation of magnetosonic waves in the meridian plane of a rescaled dipole magnetic field is investigated, for the first time, using a general curvilinear particle-in-cell simulation. Our simulation demonstrates that the magnetosonic waves are excited near the equatorial plane by tenuous ring distribution protons. The waves propagate nearly perpendicularly to the background magnetic field along both radially inward and outward directions. Different speeds of inward and outward propagation result in the asymmetrical distribution about the source region. The waves are accompanied by energization of both cool protons and electrons near the wave source region. The cool protons are heated perpendicularly, while the cool electrons can be heated in the parallel direction and also experience enhanced perpendicular drift at the presence of intense wave power. The implications of simulation results to the observations of magnetosonic waves and related particle heating in the inner magnetosphere are also discussed. ©2018 American Geophysical Union. All Rights Reserved.