A new look at physical layer security, caching, and wireless energy harvesting for heterogeneous ultra-dense networks

Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low latency through the use of dense sub-6 GHz and millimeter-wave small cells with different antenna configurations. Existing work has widely studied spectral and energy efficiency in such networks and shown that high spectral and energy efficiency can be achieved. This article investigates the benefits of heterogeneous ultra-dense network architecture from the perspectives of three promising technologies, physical layer security, caching, and wireless energy harvesting, and provides an enthusiastic outlook toward application of these technologies in heterogeneous ultra-dense networks. Based on the rationale of each technology, opportunities and challenges are identified to advance the research in this emerging network

Significantly Increased CO₂ Adsorption Performance of Nanostructured Templated Carbon by Tuning Surface Area and Nitrogen Doping

Carbon dioxide adsorption properties of a series of templated carbon adsorbents with high Brunauer–Emmett–Teller surface areas (1361–3840 m²/g) and with/without nitrogen doping (6–7 wt % N) were systematically studied. Two linear relationships between CO₂ adsorption capacities and surface areas of nitrogen-doped/undoped nanostructured templated carbons were first established. The doped nitrogen was present in the forms of pyridinic nitrogen, pyrrolic/pyridonic nitrogen, quaternary nitrogen, and an oxidized form of nitrogen. The interaction energies with CO₂, as approximated by the isosteric heats of adsorption, were increased from 30 kJ/mol on the undoped carbon to 50 kJ/mol on the N-doped carbon as a result of these nitrogen sites. The increased interactions led to an enhancement in CO₂ adsorption capacity by a factor of 2, while N₂ uptake was not enhanced. The optimized N-doped templated carbon, N-TC-EMC, possessed remarkable CO₂ capacity (4 mmol/g at 1 atm and 298 K) and selectivity (CO₂/N₂ at 1 atm = 14). Postdoping ammonia treatment was found beneficial to CO₂ adsorption. CO₂ performance of N-doped carbon under wet condition and conditions relevant to flue gas, rates of adsorption, and regeneration requirement, which are important for practical applications, were also investigated. The results showed that N-doped templated carbon exhibited all prerequisite attributes for CO₂ capture and storage applications: high CO₂ capacity and CO₂/N₂ selectivity, fast and reversible adsorption, thermal and moisture stabilities, and ease in CO₂ desorption

Prediction of the Effective Thermal Conductivity of Hollow Sphere Foams

Microscale and mesoscale hollow sphere foam (HSF) materials have attracted tremendous attention in recent decades due to their potential applications. Here, we study the effective thermal conductivity (ETC) of HSFs using an equivalent model, in which hollow spheres are first treated as equivalent solid particles, and then are combined with the ETC models that have been previously developed for solid particle filled composites. Compared with the rule of mixture model and syntactic foam models, this model shows better accuracy in predicting the ETC of HSFs. The theoretical model, together with finite element simulations, is then used to guide the design of HSFs. The results show that smaller size (nanoscale), lower packing fraction, lower shell conductivity, larger shell porosity, longer binder length, and higher interfacial thermal resistance lead to significantly lower ETC, while packing pattern, sphere size distribution, pore size of the porous shell, and binder radius have relatively minor influences. Moreover, size effects are investigated to use the proposed model for microscale and nanoscale problems. Aside from the well-known Knudsen effect, the size effect induced by interfacial thermal resistance should also be considered when the sphere size is smaller than a critical length. Interestingly, the Knudsen effect in the pores of a porous shell is shown to have an insignificant influence on the ETC. This study provides deep understanding of the thermal (and electrical, equivalently) behavior of the HSFs, which will potentially aid future design of novel and multifunctional HSF materials

Phagocytosis of neutrophils against HvKP-K1, HvKP-K2 and cKP.

<p>The rate of phagocytosis against cKP (15 isolates) was higher than that against HvKP-K1 (16 isolates) or HvKP-K2 (14 isolates) at 10, 30, 60 min. The mean ± standard deviation (S.D.) of each group at each time point was calculated respectively. Statistics was performed using one-way analysis of variance for each time point. Differences between groups were assessed by <i>t</i> test. At 10, 30, 60 min, HvKP-K1 vs. cKP or HvKP-K2 vs. cKP: p < 0.05.</p

Assessment of the proliferation rates of BASCs isolated from different animal groups by real-time cell analysis.

<p>Assessment of the proliferation rates of BASCs isolated from different animal groups by real-time cell analysis.</p

NETs under scanning electron microscopy.

<p>NETs induced by PMA (A and B), cKP (3 isolates, C and D), and HvKP-K1 (3 isolates, E and F). More cKP (C) than HvKP-K1 (E) were trapped in NETs by magnification of 5K. The pores (indicated by white arrows) on the surface of cKP, but not on the surface of HvKP-K1 were observed by magnification of 20K (D and F). Bacteria were indicated by black arrows.</p

The effect of remote limbo ischemic preconditioning on blood gas analysis.

<p>The effect of remote limbo ischemic preconditioning on blood gas analysis.</p

Assessment of lung injury in different animal groups.

<p>Comparison of the total BAL protein levels (a), lung injury scores (b) and lung weight-to-dry weight values (c) among the three groups. (d) H&E staining of lung tissues obtained from different groups at 20× and 40× magnification. *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001; ****, P ≤ 0.0001.</p

Investigation on Hydrogenation of Metal–Organic Frameworks HKUST-1, MIL-53, and ZIF‑8 by Hydrogen Spillover

The stabilities of three moisture-stable MOFs containing different metal clusters, i.e., HKUST-1 (Cu), MIL-53­(Al), and ZIF-8 (Zn), were investigated in dihydrogen and dissociated hydrogen (caused by doped Pt nanoparticles) environments. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray-excited Auger electron spectroscopy (XAES) results showed that all three MOFs were stable in dihydrogen environment. However, the structure of Pt-doped HKUST-1 collapsed in the presence of dissociated hydrogen due to the higher reduction potential of Cu compared with H, and the degree of reduction that occurred to the divalent copper in HKUST-1 increased with temperature. Unlike HKUST-1, MIL-53 and ZIF-8 maintained their structures in both dihydrogen and dissociated hydrogen environments at temperatures up to 150 °C. Moreover, comparison of Pt-doped HKUST-1 samples synthesized by chemical vapor deposition (CVD) and incipient wetness impregnation showed that the contact between the doped Pt particles (dissociation source) and MOFs (receptor) significantly affected hydrogen spillover

Analysis of serum inflammatory cytokine levels in different animal groups.

<p>(A), control; (B), CPB group; (C) treatment group. The levels of different cytokines are expressed as percentages. Each circle represents 1% of the combined level of all nine cytokines assayed.</p