An eco-friendly and efficient route of lignin extraction from black liquor and a lignin-based copolyester synthesis

Traditional method for extraction of lignin from black liquor in chemical pulping processes requires a huge amount of toxic inorganic acids like sulfuric acid which are potentially harmful to our environment and life. Furthermore, the traditional method always contains multiple steps, and thus it is time-consuming process. With a purpose to eliminate all these above disadvantages, in this study, we successfully developed an efficient process for the extraction of lignin from black liquor using a non-toxic aluminum potassium sulfate dodecahydrate (AlK(SO₄)₂·12H₂O). The developed process is simple, efficient, and short-time, which obviously have more advantages over the traditional extraction method. Furthermore, the lignin extracted in this study was used to synthesize a copolyester through polyesterification between lignin and sebacoyl chloride. The copolymer possesses a molecular weight of 31,800, corresponding to four to five repeating units of lignin macromonomers. Notably, it showed a good thermal stability up to 200 °C in TGA analysis. It was also possible to shape the copolymer using solvent casting. We believe that this newly developed method of lignin extraction may exploit new applications for eco-friendly sustainable materials in various fields.     

Energy efficiency improvement of dimethyl ether purification process by utilizing dividing wall columns

The alternative fuel, dimethyl ether (DME), which can be synthesized from natural gas, coal or biomass syngas, has been traditionally used as a diesel substitute or additive. DME purification processes with a conventional distillation sequence consume a large amount of energy. We used dividing wall columns (DWCs) to improve the energy efficiency and reduce the capital cost of the DME purification process. Various possible DWC arrangements were explored to find the potential benefits derived from thermally coupled distillations. The results show that utilizing DWCs can significantly reduce both the energy consumption and investment cost of the DME purification process. The lower energy consumption also results in the reduction of the CO₂ emission.     

Synthesis of single-crystal SnO2 nanowires for NOx gas sensors application

Single-crystal SnO₂ nanowires (NWs) were successfully synthesized and characterized as sensing materials for long-term NO_x stability detection in environmental monitoring. Reproducible and selective growths of the SnO₂ NWs on a patterned, 5 nm-thick gold catalyst coated on a SiO₂/Si wafer as substrate were conducted by evaporating SnO powder source at 960 °C in a mixture of argon/oxygen ambient gas (Ar: 50 sccm/O₂: 0.5 sccm). The as-obtained products were characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman scattering, and photoluminescence (PL). The SEM and HRTEM images revealed that the products are single-crystal SnO₂ NWs with diameter and length ranges of 70 nm–150 nm and 10 μm–100 μm, respectively. The three observed Raman peaks at 476, 633, and 774 cm⁻¹ indicated the typical rutile phase, which is in agreement with the XRD results. The NWs showed stable PL with an emission peak centered at around 620 nm at room-temperature, indicating the existence of oxygen vacancies in the NW samples. The electrical properties of synthesized SnO₂ NWs sensor were also investigated and it exhibited a negative temperature coefficient of resistance in the measured range (300–525 K). The calculated activation energy E_c of SnO₂ NWs was 0.186 eV. Moreover, the SnO₂ NW sensors exhibited good response to NO_x gas. The response of the sensors to 5 ppm NO_x reached 105% at an operating temperature of 200 °C.     

Downlink Performance Analysis of MIMO Relaying Networks

In recent years, there has been an upsurge of interest in relay-augmented infrastructure-based networks. On the other hand, multiple-input-multiple-output (MIMO) wireless system becomes a hot topic for it can achieve significant increases in overall system performance. This paper gives a detailed analysis of downlink performance of MIMO relaying networks, in which different channel models and classic MIMO cellular system model with fixed relay are considered. Our results in single cell scenario show that when meeting effective relay system efficiency of 100%, the required relay SNR gain of 2-antenna system can be reduced to less than half of that with only one transceiver antenna. We also observe that MIMO is more tolerant to interference compared with the one-transceiver antenna system. After that, multi-hop architecture is researched and statistics figures out the tolerable number of hops which is supported in wireless communication with a view to real application. In addition, multi-cell scenario is also studied. Statistics results show that there is more 8 dB average spectral efficiency gain in a two-hop fixed relay 4 × 4 MIMO system than that in a SISO system. These results present significant indications in deployment and optimization of relay-based MIMO networks.     

Conjugated Polymer Based Nanoparticles as Dual‐Modal Probes for Targeted In Vivo Fluorescence and Magnetic Resonance Imaging

A facile strategy is developed to synthesize dual‐modal fluorescent‐magnetic nanoparticles (NPs) with surface folic acid by co‐encapsulation of a far‐red/near‐infrared (FR/NIR)‐emissive conjugated polymer (PFVBT) and lipid‐coated iron oxides (IOs) into a mixture of poly(lactic‐co‐glycolic‐acid)‐poly(ethylene glycol)‐folate (PLGA‐PEG‐FOL) and PLGA. The obtained NPs exhibit superparamagnetic properties and high fluorescence, which indicates that the lipid coated on IOs is effective at separating the conjugated polymer from IOs to minimize fluorescence quenching. These NPs are spherical in shape with an average diameter of ≈180 nm in water, as determined by laser light scattering. In vitro studies reveal that these dual‐modal NPs can serve as an effective fluorescent probe to achieve targeted imaging of MCF‐7 breast cancer cells without obvious cytotoxicity. In vivo fluorescence and magnetic resonance imaging results suggest that the NPs are able to preferentially accumulate in tumor tissues to allow dual‐modal detection of tumors in a living body. This demonstrates the potential of conjugated polymer based dual‐modal nanoprobes for versatile in vitro and in vivo applications in future.     

Multifunctional Mesoporous Silica Nanoparticles for Cancer‐Targeted and Controlled Drug Delivery

Multifunctional mesoporous silica nanoparticles are developed in order to deliver anticancer drugs to specific cancer cells in a targeted and controlled manner. The nanoparticle surface is functionalized with amino‐β‐cyclodextrin rings bridged by cleavable disulfide bonds, blocking drugs inside the mesopores of the nanoparticles. Poly(ethylene glycol) polymers, functionalized with an adamantane unit at one end and a folate unit at the other end, are immobilized onto the nanoparticle surface through strong β‐cyclodextrin/adamantane complexation. The non‐cytotoxic nanoparticles containing the folate targeting units are efficiently trapped by folate‐receptor‐rich HeLa cancer cells through receptormmediated endocytosis, while folate‐receptor‐poor human embryonic kidney 293 normal cells show much lower endocytosis towards nanoparticles under the same conditions. The nanoparticles endocytosed by the cancer cells can release loaded doxorubicin into the cells triggered by acidic endosomal pH. After the nanoparticles escape from the endosome and enter into the cytoplasm of cancer cells, the high concentration of glutathione in the cytoplasm can lead to the removal of the β‐cyclodextrin capping rings by cleaving the pre‐installed disulfide bonds, further promoting the release of doxorubicin from the drug carriers. The high drug‐delivery efficacy of the multifunctional nanoparticles is attributed to the co‐operative effects of folate‐mediated targeting and stimuli‐triggered drug release. The present delivery system capable of delivering drugs in a targeted and controlled manner provides a novel platform for the next generation of therapeutics.     

Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

This paper investigates the influence of crack geometry, crack-face and loading conditions, and the permittivity of a medium inside the crack gap on intensity factors of planar and non-planar cracks in linear piezoelectric media. A weakly singular boundary integral equation method together with the near-front approximation is adopted to accurately determine the intensity factors. Obtained results indicate that the non-flat crack surface, the electric field, and the permittivity of a medium inside the crack gap play a crucial role on the behavior of intensity factors. The mode-I stress intensity factors (K_{\mathrm{I}}) for two representative non-planar cracks under different crack-face conditions are found significantly different and they possess both upper and lower bounds. In addition, K_{\mathrm{I}} for impermeable and semi-permeable non-planar cracks treated depends strongly on the electric field whereas those of impermeable, permeable, and semi-permeable penny-shaped cracks are identical and independent of the electric field. The stress/electric intensity factors predicted by permeable and energetically consistent models are, respectively, independent of and dependent on the electric field for the penny-shaped crack and the two representative non-planar cracks. Also, the permittivity of a medium inside the crack gap strongly affects the intensity factors for all crack configurations considered except for K_{\mathrm{I}} of the semi-permeable penny-shaped crack.     

Simulating secondary organic aerosol activation by condensation of multiple organics on seed particles

The conditions under which semivolatile organic gases condense were studied in a Teflon particle chamber by scanning mobility particle sizing (SMPS) of the resultant particles. Benzaldehyde, maleic and citraconic anhydrides, n-decane, trans-cinnamaldehyde, and citral were introduced in various combinations into a particle chamber containing either particle-free nitrogen or nitrogen with dry seed particles made out of sodium chloride, D-tartartic acid, ammonium sulfate, or 1,10-decanediol. No organic gas was allowed to reach its saturation point relative to the vapor pressure of its pure liquid in any experiment. In the absence of seed particles, organic aerosol particles formed by ternary nucleation when the sum of the individual organic saturation levels reached a threshold between 1.17 and 1.86. With seed particles present, particle sizes began to increase when the sum of organic saturation levels reached 1.0. This size increase corresponds to the establishment and activation of ternary organic layers on the "clean" seed particles, as predicted by absorption partitioning theory. The observed increases in particle volume depended on initial seed particle volume, indicating that either gas diffusion rates or chemical reactions were controlling the rate of uptake.