Electrically insulating polymer dielectrics with high energy densities and excellent thermal conductivities are showing tremendous potential for dielectric energy storage. However, the practical ...application of polymer dielectrics often requires mutually exclusive multifunctional properties such as high dielectric constants, high breakdown strengths, and high thermal conductivities. The rational assembly of 2D nanofillers of boron nitride nanosheets (BNNS) and reduced graphene oxide (rGO) into a well‐aligned micro‐sandwich structure in polyimide (PI) composites is reported. The alternating stacking of rGO and BNNS synergistically exploits the large difference in their electrical conductivities to yield a high dielectric constant with a moderate breakdown strength. Moreover, the distinctively separated rGO and BNNS layers give rise to higher thermal conductivities of composites than those containing mixed fillers because of reduced phonon scattering at the interfaces between two identical fillers, as verified by molecular dynamics simulations. Consequently, the micro‐sandwich nanocomposite prevails over the PI film with a simultaneously high dielectric constant of ≈579, a high energy density (43‐fold higher than PI) and an excellent thermal conductivity (11‐fold higher than PI) at a low hybrid filler content of only 2.5 vol%. The multifunctional nanocomposites developed in this work are promising for flexible dielectrics with excellent heat dissipation.
Multifunctional micro‐sandwich composites with a high thermal conductivity, a high dielectric constant, and a low dielectric loss are developed with alternatingly stacked reduced graphene oxide (rGO) and boron nitride nanosheets (BNNS) layers in a polyimide matrix. The synergistic alignments of rGO and BNNS result in a high energy density and an excellent thermal management capability for flexible dielectrics.
Polypyrrole (PPy)/graphene (GR) nanocomposites were successfully prepared via in-situ polymerization of graphite oxide (GO) and pyrrole monomer followed by chemical reduction using hydrazine ...monohydrate. The large surface area and high aspect ratio of the in-situ generated graphene played an important role in justifying the noticeable improvements in electrical conductivity of the prepared composites via chemical reduction. X-ray photoelectron spectroscopy (XPS) analysis revealed the removal of oxygen functionality from the GO surface after reduction and the bonding structure of the reduced composites were further determined from FTIR and Raman spectroscopic analysis. For PPy/GR composite, intensity ratio between D band and G band was high (∼1.17), indicating an increased number of c-sp
2 domains that were formed during the reduction process. A reasonable improvement in thermal stability of the reduced composite was also observed. Transmission electron microscopy (TEM) observations indicated the dispersion of the graphene nanosheets within the PPy matrix.
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Abstract
In long-haul optical communication systems, compensating nonlinear effects through digital signal processing (DSP) is difficult due to intractable interactions between Kerr nonlinearity, ...chromatic dispersion (CD) and amplified spontaneous emission (ASE) noise from inline amplifiers. Optimizing the standard digital back propagation (DBP) as a deep neural network (DNN) with interleaving linear and nonlinear operations for fiber nonlinearity compensation was shown to improve transmission performance in idealized simulation environments. Here, we extend such concepts to practical single-channel and polarization division multiplexed wavelength division multiplexed experiments. We show improved performance compared to state-of-the-art DSP algorithms and additionally, the optimized DNN-based DBP parameters exhibit a mathematical structure which guides us to further analyze the noise statistics of fiber nonlinearity compensation. This machine learning-inspired analysis reveals that ASE noise and incomplete CD compensation of the Kerr nonlinear term produce extra distortions that accumulates along the DBP stages. Therefore, the best DSP should balance between suppressing these distortions and inverting the fiber propagation effects, and such trade-off shifts across different DBP stages in a quantifiable manner. Instead of the common ‘black-box’ approach to intractable problems, our work shows how machine learning can be a complementary tool to human analytical thinking and help advance theoretical understandings in disciplines such as optics.
Oncogenic mutations in PIK3CA, the gene encoding the catalytic subunit of phosphoinositide 3-kinase (PI3K), occur with high frequency in breast cancer. The protein kinase Akt is considered to be the ...primary effector of PIK3CA, although mechanisms by which PI3K mediates Akt-independent tumorigenic signals remain obscure. We show that serum and glucocorticoid-regulated kinase 3 (SGK3) is amplified in breast cancer and activated downstream of PIK3CA in a manner dependent on the phosphoinositide phosphatase INPP4B. Expression of INPP4B leads to enhanced SGK3 activation and suppression of Akt phosphorylation. Activation of SGK3 downstream of PIK3CA and INPP4B is required for 3D proliferation, invasive migration, and tumorigenesis in vivo. We further show that SGK3 targets the metastasis suppressor NDRG1 for degradation by Fbw7. We propose a model in which breast cancers harboring oncogenic PIK3CA activate SGK3 signaling while suppressing Akt, indicative of oncogenic functions for both INPP4B and SGK3 in these tumors.
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•SGK3 is amplified in breast cancer•The lipid phosphatase INPP4B mediates SGK3 activation downstream of PIK3CA•SGK3 promotes proliferation and growth of breast cancer cells in vitro and in vivo•The stability of the metastasis suppressor NDRG1 is regulated by SGK3 activity
Oncogenic mutations in PIK3CA occur with high frequency in cancer. Gasser et al. show that serum and glucocorticoid-regulated kinase 3 (SGK3) is amplified in breast cancer and functions downstream of PIK3CA and the phosphoinositide phosphatase INPP4B. INPP4B is required for SGK3 activation, providing evidence for both INPP4B and SGK3 functioning as oncogenes.
We investigated the effect of carbon nanotube (CNT) modifications on the flexural and wear behaviors of multiscale carbon/CNT/epoxy composites in this study. Carbon/epoxy woven composites and two ...types of multiscale carbon/CNT/epoxy composites were fabricated by incorporating woven-type carbon fibers into epoxy matrices modified with 2wt% acid-treated and silane-treated multi-walled carbon nanotubes (MWCNTs). Three-point bending and ball-on-disk wear tests were performed on the three composites. The results showed that the flexural moduli and strengths of carbon/CNT/epoxy composites were greater than those of carbon/epoxy composites, regardless of CNT modification. Specifically, the flexural modulus and strength of the silane-treated specimens were 10% and 15% greater, respectively, than those of the acid-treated samples. The results also showed that the wear properties of carbon/epoxy composites are improved by the addition of CNTs. In addition, the wear properties of silane-treated samples were superior to those of acid-treated samples. Scanning electron microscopic examination of fractured and worn surfaces showed that the improvement in the flexural and wear properties of the silane-treated carbon/CNT/epoxy composites was attributed to the improved dispersion of CNTs in the epoxy and the better interfacial characteristics caused by the silanization of the CNTs.
Intercellular communication can occur through gap junction channels, which are comprised of connexin proteins. Therefore, levels of connexins can directly correlate with gap junctional intercellular ...communication. Because gap junctions have a critical role in maintaining cellular homeostasis, the regulation of connexin protein levels is important. In the connexin life cycle, connexin protein levels can be modified through differential gene transcription or altered through trafficking and degradation mechanisms. More recently, significant attention has been directed to the pathways that cells utilize to increase or decrease connexin levels and thus indirectly, gap junctional communication. Here, we review the studies revealing the mechanisms that affect connexin protein levels and gap junctional intercellular communication.
•A simplified micro model for masonry assemblages is proposed.•The model is used for hollow and grouted prisms, shear and diagonal tension specimens.•Mortar joints and units are smeared into one ...homogeneous material.•The model relies on CDP and surface-based cohesive behavior for units and interface elements.•The proposed model can be successfully used to model grouted, ungrouted and partially grouted masonry walls.
Masonry is an anisotropy structure due to the presence of different components within the assembly. Although, the concepts of concrete modeling are applicable to fully grouted masonry there are difficulties for modeling hollow and partially grouted masonry. Cohesive surface-based behavior (interface elements) has been used in this study as a discontinuity for hollow and grouted masonry. The mortar joints and concrete masonry units were smeared into one homogeneous material using concrete damage plasticity model (CDP). The traction–separation behavior of the cohesive element was employed to model the mortar joints. Damage initiation was considered based on compressive strength of mortar and grout in the hollow and grouted masonry, respectively. A set of tests were conducted on masonry assemblages and properties were used as input in the model. It is evident from results that the responses predicted by the analysis are generally in good agreement with the behavior observed in the experiments for the hollow and grouted prisms, shear and diagonal tension assemblages. The proposed model can be successfully used to model hollow and partially grouted masonry walls.
Aberrant Skp2 signaling has been implicated as a driving event in tumorigenesis. Although the underlying molecular mechanisms remain elusive, cytoplasmic Skp2 correlates with more aggressive forms of ...breast and prostate cancers. Here, we report that Skp2 is acetylated by p300 at K68 and K71, which is a process that can be antagonized by the SIRT3 deacetylase. Inactivation of SIRT3 leads to elevated Skp2 acetylation, which leads to increased Skp2 stability through impairment of the Cdh1-mediated proteolysis pathway. As a result, Skp2 oncogenic function is increased, whereby cells expressing an acetylation-mimetic mutant display enhanced cellular proliferation and tumorigenesis in vivo. Moreover, acetylation of Skp2 in the nuclear localization signal (NLS) promotes its cytoplasmic retention, and cytoplasmic Skp2 enhances cellular migration through ubiquitination and destruction of E-cadherin. Thus, our study identifies an acetylation-dependent regulatory mechanism governing Skp2 oncogenic function and provides insight into how cytoplasmic Skp2 controls cellular migration.
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► Skp2 is acetylated by p300 at K68 and K71 within the nuclear localization signal ► SIRT3 interacts with and deacetylates Skp2 ► Acetylation stabilizes Skp2 and promotes its cytoplasmic localization ► Skp2 promotes cell migration through regulation of E-cadherin degradation
Acetylation of the E3 ubiquitin ligase Skp2 leads to its cytoplasmic retention. This enhances the ubiquitin-mediated destruction of the adhesion molecule E-cadherin, thereby promoting cell migration during tumorigenesis.
Muscles act as a cushioning layer protecting most of our brittle bones and delicate visceral organs. Inspired by the internal architecture of skeletal muscle tissues, a novel tubular section design ...with structural hierarchy was recently proposed for impact protection (Tsang and Raza, 2018). This paper presents a fundamental experimental investigation of the force resistance and energy absorption capabilities of the proposed hierarchical structure. A soft and ductile thermoplastic polyurethane (TPU) with Shore-A hardness of 95 is used for three-dimensional (3D) printing of the specimens. The enhanced force resistance and energy absorption are then quantified based on the hysteretic behaviour observed in a series of quasi-static compression tests with loading and unloading. The superior force resistance and energy absorption capabilities of the muscle-inspired hierarchical structure are proven.
We propose a blind transmitter (Tx) and receiver (Rx) in-phase/quadrature (IQ) amplitude and phase imbalances estimation scheme based on a combination of analytical modeling and clustering ...algorithms. The proposed scheme can isolate and separately estimate Tx and Rx phase and amplitude imbalances, applicable to high-order multi-modulus signals, and hence, is a great physical-layer-monitoring tool for network disaggregation. We first estimate the Rx imbalances by identifying the fact that the received signal distribution in presence of laser frequency offset (FO), phase noise (PN), and Rx imbalance forms concentric ellipses. A convex hull assisted ellipse correction algorithm is used to determine the Rx IQ imbalance parameters that best match the ellipses. Standard laser FO compensation algorithm follows. A k-means clustering assisted blind phase search algorithm is then employed to mitigate the PN in presence of Tx imbalances. Finally, another iterative k-means clustering procedure is used to estimate the Tx IQ imbalances. The proposed scheme is evaluated experimentally for 34 Gbaud QPSK and 16-quadratic-amplitude modulation signals. The accurate estimation for a wide range of Tx and Rx IQ imbalances and good robustness to amplified spontaneous emission noise is demonstrated.
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