An adaptive digital beamforming (DBF) array is vital in advanced wireless systems. Beamforming problems in DBF arrays could be time-consuming and inflexible, as most of them are only solvable by ...optimization algorithms. In this letter, we propose an improvement to this issue in solving wide nulling problems of an adaptive DBF array by building a data-based wide nulling model using a powerful optimization algorithm - the Bat algorithm (BA) with the general regression neural network (GRNN). The BA efficiently generates the necessary full complex weights as training samples to train the model. The GRNN estimates the data in the gaps of training samples and gives an efficient and flexible estimation. A 32-element uniform linear array is used an example to demonstrate the proposed algorithm. Numerical experimental results show that the data-based model is functional with an acceptable performance for all test cases and achieves a much better time efficiency in comparison to using solely the BA in determining the complex weights to wide nulling problems.
Paraffin/carbon foam composite phase change material (PCM) was prepared with vacuum assistance in the present study, and the structure and thermo-physical properties of the composite PCM were ...studied. The impregnation ratios were studied comparatively for the cases with and without vacuum assistance, and the results showed that the impregnation process with vacuum assistance was superior to that without vacuum assistance. Micro-Computed Tomography (Micro-CT) technique was used to investigate the inner structural characteristics of the composite PCM. The gray value analysis was conducted, and two dimensional (2D) cross-section images and three dimensional (3D) renderings were constructed accordingly. Both the surface porosity and bulk porosity were obtained from the image analysis. Compared with pure paraffin, the thermal conductivity of the composite PCM was enhanced, e.g., the composite PCM with vacuum assistance was about three times larger than that of pure paraffin. The measured thermal conductivity showed agreement with the theoretical models. The phase change behaviors of the composite PCM were investigated with a differential scanning calorimeter (DSC). The presence of the porous carbon foam affected the phase change behavior of pure paraffin in that the extrapolated onset melting/freezing temperatures shifted from 52.10/60.56°C for pure paraffin to 51.73/61.16°C. The thermal effusivity of the composite PCM was larger than that of pure paraffin, which was apparently advantageous for latent thermal energy storage (LTES).
•Paraffin/carbon foam composite PCM was prepared with vacuum assistance.•Some shrinking regions in the inner of composite PCM were observed with Micro-CT.•The thermal conductivity of composite PCM was enhanced.•The solid–liquid phase change temperature of composite PCM showed no distinct shift.
RSK1, a downstream kinase of the MAPK pathway, has been shown to regulate multiple cellular processes and is essential for lytic replication of a variety of viruses, including Kaposi's ...sarcoma-associated herpesvirus (KSHV). Besides phosphorylation, it is not known whether other post-translational modifications play an important role in regulating RSK1 function. We demonstrate that RSK1 undergoes robust SUMOylation during KSHV lytic replication at lysine residues K110, K335, and K421. SUMO modification does not alter RSK1 activation and kinase activity upon KSHV ORF45 co-expression, but affects RSK1 downstream substrate phosphorylation. Compared to wild-type RSK1, the overall phosphorylation level of RxRxxS*/T* motif is significantly declined in RSK1K110/335/421R expressing cells. Specifically, SUMOylation deficient RSK1 cannot efficiently phosphorylate eIF4B. Sequence analysis showed that eIF4B has one SUMO-interacting motif (SIM) between the amino acid position 166 and 170 (166IRVDV170), which mediates the association between eIF4B and RSK1 through SUMO-SIM interaction. These results indicate that SUMOylation regulates the phosphorylation of RSK1 downstream substrates, which is required for efficient KSHV lytic replication.
ZNF804A (zinc-finger protein 804A) has been recognized as a schizophrenia risk gene across multiple world populations. Its intronic single-nucleotide polymorphism (SNP) rs1344706 is among one of the ...strongest susceptibility variants that have achieved genome-wide significance in genome-wide association studies (GWAS) for schizophrenia and has been widely and intensively studied. To elucidate the biological mechanisms underlying the genetic risk conferred by rs1344706, we retrospectively analyzed the progresses in brain gene expression quantitative trait loci (eQTL) analyses, ZNF804A-induced pathway alterations in neural cells and changes in synaptic phenotypes associated with ZNF804A expression. Based on these data, we hypothesize a potential biological mechanism for a genetic risk allele of ZNF804A in schizophrenia pathogenesis. We also review the efforts being made to characterize the affected intermediate phenotypes using neuroimaging and neuropsychological approaches. We then discuss additional common and rare ZNF804A variants in schizophrenia susceptibility and the potential genetic heterogeneity of these genomic loci between Europeans and Asians. This review for we believe the first time systematically presents the evidence for ZNF804A, describing its discovery and likely roles in brain development and schizophrenia pathogenesis. We believe that this work has summarized this information with a systemic and broad assessment of recent findings.
Biodegradable polylactic acid (PLA) mulch has been developed to replace conventional polyethylene (PE) mulch in agriculture as a response to growing concerns about recalcitrant plastic pollution and ...the accumulation of microplastics (MPs) in soil. Cadmium is a significant soil pollutant in China. MPs have been shown to adsorb metals. In this study the earthworm Lumbricus terrestris was exposed to either Cd (1.0–100 mg / kg) or MPs (PE and PLA, 0.1–3 % w / w), or a combination of the two, for 28 days. Cd bioavailability significantly decreased in the presence of MPs. In particular, at the end of the experiment, PLA treatments had lower measured Cd concentrations in both earthworms (2.127–29.24 mg / kg) and pore water (below detection limits - 0.1384 mg /L) relative to PE treatments (2.720–33.77 mg / kg and below detection limits - 0.2489 mg / L). In our adsorption experiment PLA MPs adsorbed significantly more Cd than PE MPs with maximum adsorption capacities of 126.0 and 23.2 mg / kg respectively. These results suggest that the PLA MPs reduce earthworm exposure to Cd relative to PE by removing it from solution and reducing its bioavailability.
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•Realistic levels of MP in soils did not impact earthworm mortality or weight change.•The presence of MPs decreased Cd concentrations in both earthworms and pore water.•PLA MPs decreased Cd accumulation in earthworms relative to PE MPs.•PLA MPs adsorbed significantly more Cd than PE MPs.
The mechanical degradation of electrodes caused by lithiation and delithiation is one of the main factors responsible for the short cycle life of lithium-based batteries employing high capacity ...electrodes. In this report, we introduced a simple patterning approach to improve the cycling stability of silicon electrode, which is considered as the next generation negative electrode due to its high Coulombic capacity and low cost, but is limited by the mechanical degradation associated with large volume variations during cycling. The pattern design is based on the observation of a critical size for the crack gap in continuous films. An improvement in cycle life was noted when the pattern size was below the critical (7–10
μm) size, in which case the Si electrode patches adhered well to the Cu substrate after many cycles. By taking the plastic deformation in both Si thin film and substrate into consideration, the calculated crack spacing is consistent with experimental observations. Theoretical considerations gave a feasible explanation for the failure of Si pattern above the critical size. These results suggest a new approach to extend the cycle life of Si-based electrode materials using size to control and relax the stress due to lithiation and delithiation.
•Thermal conductivity of nitrate/EG composite was accurately measured by considering thermal contact resistance.•Heat storage and retrieval tests were conducted with binary nitrates and nitrates/EG ...composites.•A comprehensive model was built to interpret the heat transfer characteristics.
Eutectic molten salt can be used as the latent thermal energy storage medium in solar energy applications. Nitrates and their binary mixtures are suitable phase change material (PCM) for solar energy applications in middle-temperature-range of 200–300°C. In the present study, binary nitrate (50wt.% NaNO3, 50wt.% KNO3) with a melting temperature of about 220°C was employed as the PCM, and expanded graphite (EG) with the mass fraction of 5%, 10% or 20% was used to enhance the thermal conductivity. The thermal conductivities of pure nitrates and nitrate/EG shape-stabilized composites were measured with a steady-state test rig firstly. Results showed that the addition of EG significantly enhanced the thermal conductivities, e.g., the thermal conductivities of sodium nitrate/20wt.% EG composite PCM were measured to be 6.66–7.70W/(mK) in the temperature range of 20–120°C, indicating about seven times larger than those of pure sodium nitrate. Furthermore, pure binary nitrate and nitrate/EG composite PCM were encapsulated in a cylindrical storage unit with a diameter of 70.0mm and a length of 280.0mm. Heat storage and retrieval tests were conducted extensively at different heating temperatures of 250°C, 260°C and 270°C, and different cooling temperatures of 30°C, 70°C and 110°C. Time-durations from temperature evolutions showed that both the melting and solidification processes were accelerated by EG, and the heat transfer characteristics were interpreted by the numerical analysis based on enthalpy–porosity and volume-of-fluid models. The evolution of nitrate/air interface caused by volume expansion ascended gradually during melting, while that caused by volume shrinkage descended during freezing.
This paper is the second portion of a two-part study of the heat transfer characteristics of a shell-tube LTES (latent thermal energy storage) system. The three-dimensional model was used to ...investigate the discharging characteristics of the LTES system. Pure paraffin and paraffin/expanded graphite (EG) composite PCMs with 7 wt. % and 10 wt. % EG were used as the PCMs (phase change materials), and water filled in a cylindrical tank was used as the HTF (heat transfer fluid). A variety of numerical investigations were conducted under different conditions for heat retrieval, such as different inlet temperatures and flow rates of the HTF, different initial temperatures of the LTES system. The experimental and numerical results of the temperature evolutions inside the tank were compared extensively, which proved that the enthalpy model developed can accurately predict the thermo-fluidic behaviors of the LTES system for heat retrieval. The inlet temperatures and flow rates of the HTF significantly influenced the time-durations of the discharging process, while the initial temperature of the system had slight influence. Furthermore, the heat transfer coefficients between the HTF and PCM tubes were estimated at various heights and moments, which could be useful information for LTES system design.
•The discharging characteristics of a shell-tube LTES (latent thermal energy storage) system were investigated.•Numerical results showed agreement with the experimental results.•Inlet temperatures and flow rates of the cold HTF (heat transfer fluid) influenced the time-durations of the retrievals.•Heat transfer coefficients between the HTF and PCM (phase change material) were revealed extensively.
•The addition of expanded graphite improved apparent thermal conductivity significantly.•The quadratic parallel model was used to predict the effective thermal conductivity.•The melting/freezing ...temperatures of mixture PCMs shifted slightly with adding of EG.
Solar energy storage has become more attractive in recent years. In particular, latent thermal energy storage (LTES) with large energy storage density and isothermal heat storage/retrieval characteristics is a hot research topic. In the present study, sodium nitrate, potassium nitrate and their mixture were used as the base materials, and expanded graphite (EG) with high thermal conductivity and thermo-chemical stability was used as an additive to enhance the thermal conductivity. EG with various mass fractions was added to the base materials to form mixture phase change materials (PCMs), and the thermal characteristics of the mixtures were studied extensively. The transient hot-wire tests showed that the addition of EG enhanced the apparent thermal conductivity significantly, e.g. the apparent thermal conductivity of the nitrates/10wt.% EG mixture PCM was increased by about 30–40%. The test results showed good agreement with theoretical calculations of the quadratic parallel model. Tests with differential scanning calorimeter (DSC) revealed that the melting/freezing temperatures of the mixture PCMs shifted slightly, compared with those of pure nitrates.
Realizing stable two-dimensional (2D) Dirac points against spin-orbit coupling (SOC) has attracted much attention because it provides a platform to study the unique transport properties. In previous ...work, Young and Kane Phys. Rev. Lett. 115, 126803 (2015) proposed stable 2D Dirac points with SOC, in which the Berry curvature and edge states vanish due to the coexistence of inversion and time-reversal symmetries. Herein, using the tight-binding model and k·p effective Hamiltonian, we present that 2D Dirac points can survive in the presence of SOC without inversion symmetry. Such 2D Dirac semimetals possess nonzero Berry curvature near the crossing nodes, and two edge states are terminated at one pair of Dirac points. In addition, according to symmetry arguments and high-throughput first-principles calculations, we identify a family of ideal 2D Dirac semimetals, which has nonzero Berry curvature in the vicinity of Dirac points and visible edge states, thus facilitating the experimental observations. Our work shows that 2D Dirac points can emerge without inversion symmetry, which not only enriches the classification of 2D topological semimetals but also provides a promising avenue to observe exotic transport phenomena beyond graphene, e.g., nonlinear Hall effect.
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