[en] Objective: To investigate the effect of decreasing DKC1 gene expression on radiosensitivity of HeLa cells. Methods: A cell model with low expression of DKC1 gene was established by shRNA technology with lentivirus as vector, and the interference efficiency was verified by RT-PCR and Western blot assay. Cells were divided into two groups of interference (Lv-shDKC1) and its negative control. Telomerase activity was detected by TRAP-ELISA, and telomere length was measured by Real-time PCR. Cell survival was obtained through clone formation assay and fitted by multi-target single-hit model, and radiobiological parameters (D₀, D_q, N, SF₂) and radiosensitization ratio (SER) were calculated. Results: After DKC1 interfering, the expression levels of mRNA and protein of DKC1 in HeLa cells were significantly decreased by (71.330 ± 4.112)% (t = 25.53, P < 0.05) and (35.520 ± 3.804)% (t = 4.833, P < 0.05), respectively. Compared with the blank control group and negative control group, the telomerase activity of Lv-shDKC1 group decreased significantly from 0.900 ± 0.044 and 0.897 ± 0.031 to 0.713 ± 0.021 (F = 31.44, P < 0.05), the relative telomere length was significantly decreased from 4.233 ± 0.306 and 4.633 ± 0.379 to 2.667 ± 0.404 (F = 39.15, P < 0.05). The telomerase activity and relative telomere length of blank control group and Lv-shDKC1 negative control group had no significant difference (P > 0.05). SF₂ in the interference group (0.571 ± 0.006) was significantly lower than that of the blank control group (0.861 ± 0.009) and the Lv-shDKC1 negative control group (0.807 ± 0.002) (F = 1812, P < 0.05), and the radiosensitization ratio (SER) of shDKC1 interference was 1.508. Conclusions: Downregulation of DKC1 in human cervical cancer HeLa cells enhances the radiosensitivity through inhibiting the activity of telomerase and shortening the length of telomere. DKC1 gene may become a new target of radiosensitization. (authors)

[en] In this contribution, the nanopore array derived from L-cysteine oxide/gold hybrids (NA-COGH) was applied to the simultaneous determination of hydroquinone (HQ) and catechol (CT). NA-COGH was prepared by a sequential electrodeposition of L-cysteine oxide and gold into the voids of polystyrene spheres template, followed by removing the template using tetrahydrofuran. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses validated the formation of NA-COGH on the glassy carbon electrode. The charge transfer ability of NA-COGH was studied by means of scanning electrochemical microscopy (SECM). A better charge transfer rate was obtained by optimizing the electrodeposition conditions. More interestingly, the as-prepared NA-COGH presents high electrocatalytic activity for the oxidation of HQ and CT. The sensing platform based on NA-COGH shows a wide linear response for HQ and CT in the concentration range of 4.0 × 10⁻⁷–6.0 × 10⁻⁴ M and 8.0 × 10⁻⁷–5.0 × 10⁻⁴ M, with detection limit of 1.9 × 10⁻⁸ M and 3.4 × 10⁻⁸ M (S/N = 3), respectively. Rotating disk electrode experiments revealed that the catalytic rate constants were as high as 7.99 × 10⁻³ cm s⁻¹ and 7.38 × 10⁻³ cm s⁻¹ at potential of 302 mV and 416 mV for HQ and CT, respectively. With good stability and reproducibility, we applied the present method to the simultaneous determination of HQ and CT in tap water and lake water. These results indicate that NA-COGH is a promising electrode material with great potential in electrocatalysis and electrochemical sensing

[en] This work aims to design the disturbance rejection controllers for three classes of fractional heat equations. Based on Filippov’s theory, the existence conclusion for the partial differential inclusion solution (PDIS) is established for fractional heat equations with discontinuous boundary conditions. Boundary control strategies are designed directly without the use of any robust control method to respectively achieve the power-law type stabilization and the asymptotical stabilization for fractional heat equations without and with time delay, respectively. A numerical example is included to illustrate the obtained results.

[en] Silicon and related materials have recently received considerable attention as potential anodes in Li-ion batteries for their high theoretical specific capacities. To overcome the problem of volume variations during the Li insertion/extraction process, in this work, Si/C composites with low carbon content were synthesized from cheap coarse silicon and citric acid by simple ball milling and subsequent thermal treatment. The effects of ball milling time and calcination temperature on the structure, composition and morphology of the composites were systematically investigated by the determination of specific surface area (BET) and particle-size distribution, X-ray diffraction (XRD), O₂-TPO, and scanning electron microscopy (SEM). The capacity and cycling stability of the composites were systematically evaluated by electrochemical charge/discharge tests. It was found that both the initial capacity and the cycling stability of the composites were dependent on the milling and calcination conditions, and attractive overall electrochemical performance could be obtained by optimizing the synthesis process.

[en] The formation mechanism of a spinel-type lithium titanate Li₄Ti₅O₁₂ with TiO₂ anatase as raw material, in both a conventional solid-state reaction (SSR) and a cellulose-assisted glycine-nitrate combustion (cellulose-GN) process are comparatively studied. XRD characterization demonstrates high-purity Li₄Ti₅O₁₂ forms at 750 ^oC by the cellulose-GN synthesis, which occurs at a temperature at least 100 ^oC lower than that via SSR. The solid-phase reaction between TiO₂ and lithium compounds to form Li-Ti-O spinel and the phase transition of TiO₂ from anatase to 'inert' rutile phase occur competitively during both synthesis processes. SEM results suggest that the solid precursor from the cellulose-GN process has a smaller particle size and a more homogenous mixing of the reactants than that in the SSR. Temperature-programmed oxidation experiments demonstrate that cellulose thermal pyrolysis creates a reducing atmosphere, which may facilitate the oxygen-ion diffusion. Both factors facilitate the formation of Li-Ti-O spinel, while the TiO₂ anatase transforms to TiO₂ rutile during the SSR, which has slow lithium-insertion kinetics. As a result, a high calcination temperature is necessary to obtain a phase-pure Li₄Ti₅O₁₂. Charge-discharge and EIS tests demonstrate the Li₄Ti₅O₁₂ obtained by the cellulose-GN process shows much better low-temperature electrochemical performance than that obtained by standard SSR. This improvement attributes to the reduced particle size due to the lower synthesis temperature.

[en] Pure-phase spinel-type lithium titanate, Li₄Ti₅O₁₂, was successfully fabricated by cellulose-assisted glycine-nitrate (cellulose-GN) combustion process at reduced temperature using anatase TiO₂ solid as raw material of titanium. The influence of cellulose and impregnation sequence on the phase purity, particle size and electrochemical performance of Li₄Ti₅O₁₂ was investigated. The sequence of preparation was found to have big effect on the phase formation and electrochemical performance of the oxides. High-purity and well-crystallized Li₄Ti₅O₁₂ oxides were obtained at a calcination temperature of 750 deg. C via the sequence III, for which the cellulose was first adsorbed by the mixed solution of LiNO₃ and glycine followed by the impregnation of TiO₂ suspension. Compared with solid-state reaction, the cellulose-GN process produced the Li₄Ti₅O₁₂ oxides with smaller particle size and higher specific capacity due to the lower synthesis temperature. A reversible capacity of 103 mAh/g at 20 C rate and fairly stable cycling performance even at 40 C was achieved.

[en] There is increasing interest in flexible, safe, high-power thin-film lithium-ion batteries which can be applied to various modern devices. Although TiO₂ in rutile phase is highly attractive as an anode material of lithium-ion batteries for its high thermal stability and theoretical capacity of 336 mA h g⁻¹ and low price, its inflexibility and sluggish lithium intercalation kinetics of bulk phase strongly limit its practical application for particular in thin-film electrode. Here we show a simple way to prepare highly flexible self-standing thin-film electrodes composed of mesoporous rutile TiO₂/C nanofibers with low carbon content (<15 wt.%) by electrospinning technique with outstanding electrochemical performance, which can be applied directly as electrodes of lithium-ion batteries without the further use of any additive and binder. The atmosphere during calcination plays a critical role in determining the flexible nature of thin film and particle size of TiO₂ in as-fabricated nanofibers. Big size (10 cm × 4 cm), flexible thin film is obtained after heat treatment under 10%H₂–Ar at 900 °C for 3 h. After optimization, the diameter of fibers can reach as small as ∼110 nm, and the as-prepared rutile TiO₂ films show high initial electrochemical activity with the first discharge capacity as high as 388 mA h g⁻¹. What is more, very stable reversible capacities of ∼122, 92, and 70 mA h g⁻¹ are achieved respectively at 1, 5 and 10 C rates with negligible decay rate within 100 cycling times.

[en] Highlights: ► A solar-assisted methane chemically recuperated gas turbine cycle has been proposed. ► The parametric sensitivity analysis of a SOLRGT system has been carried out. ► The concept of indirect upgrading of solar heat proves to be feasible. -- Abstract: Development of novel solar–fossil fuel hybrid system is important for the efficient utilization of low temperature solar heat. A solar-assisted methane chemically recuperated gas turbine (SOLRGT) system was proposed by Zhang and co-worker, which integrated solar heat into a high efficiency power system. The low temperature solar heat is first converted into vapor latent heat provided for a reformer, and then indirectly upgraded to high-grade generated syngas chemical energy by the reformation reaction. In this paper, based on the above mentioned cycle, a parametric analysis is performed using ASPEN PLUS code to further evaluate the effect of key thermodynamics parameters on the SOLRGT performance. It can be shown that solar collector temperature, steam/air mass ratio, turbine inlet pressure, and turbine inlet temperature have significant effects on system efficiency, solar-to-electricity efficiency, fossil fuel saving ratio, specific CO₂ emission and so on. The solar collector temperature is varied between 140 and 240 °C and the maximum net solar-to-electricity efficiency and system efficiency for a given turbine inlet condition (turbine inlet temperature of 1308 °C and pressure ratio of 15) is 30.2% and 52.9%, respectively. The fossil fuel saving ratio can reach up to 21.8% and the reduction of specific CO₂ emission is also 21.8% compared to the reference system. The system performance is promising for an optimum pressure ratio at a given turbine inlet temperature.

[en] Degradation mechanisms that caused by repetitive insertion and extraction of the lithium ion on the electrodes can lead to a grand challenge for optimizing the design of silicon (Si) based anode with high capacity and rate capacity. However, with decreasing the electrode size into nanometer scale, the surface-to-volume ratio will become very high, meaning that surface effect will have a significant role in determining the mechanical behavior of the electrode. And these effects suppress crack nucleation and propagation, which may become a resistance to brittle fracture. In our work, we establish a theoretical model to study the diffusion induced stress (DIS) evolution and firstly discuss the crack growth by using stress intensity factor (SIF) coupled with surface effects. The results show that DIS, especially the tensile stress, would decrease noticeably due to the surface mechanism. Surface cracks will propagate when SIF is larger than the fracture toughness of materials. It can also be revealed that smaller particles exhibit higher structural integrity. Significantly, the critical nanoparticle electrode size is arrived, below which the anode will not be broken and this value is in good agreement with experimental observations. Overall, the present work maybe provides physical underpinnings for optimized structural design to mitigate the mechanical degradation in high-performance anodes for Li-ion batteries.

[en] This paper considers the dynamics of escape in the stochastic FitzHugh–Nagumo (FHN) neuronal model driven by symmetric α -stable Lévy noise. External or internal stimulation may make the excitable system produce a pulse or not, which can be interpreted as an escape problem. A new method to analyse the state transition from the rest state to the excitatory state is presented. This approach consists of two deterministic indices: the first escape probability (FEP) and the mean first exit time (MFET). We find that higher FEP in the rest state (equilibrium) promotes such a transition and MFET reflects the stability of the rest state directly with the selected escape region. The developed two dimensional numerical simulation method to calculate FEP and MFET can not only avoid a dimension reduction, but is also applicable for the cases with large noise. In addition, FEP provides us with a new perspective to understand the seperatrix of the stochastic FHN model. It can be seen that smaller jumps of the Lévy motion and relatively small noise intensity are conducive to the production of spikes. In order to characterize the effect of noise on the selected escape region in which the equilibrium lies, the area of higher FEP and MFET in the escape region are calculated. Meanwhile, Brownian motion as a special case is also taken into account for comparison. (paper: biological modelling and information)