[en] Highlights: • A convection-driven T-shaped standing-wave thermoacoustic system is designed and tested. • A 2D model is developed to simulate the heat-to-sound energy conversion process in such system. • Three critical parameters are examined in trigging thermoacoustic oscillations. • Hopf supercritical bifurcation is observed. • Good agreement is obtained between the numerical and experimental measurement. - Abstract: The present work considers a convection-driven T-shaped standing-wave thermoacoustic system. To gain insights on the conversion process of heat to sound and to study the nonlinear coupling between unsteady heat release and acoustic disturbances, thermodynamic analysis, numerical and experimental investigations are conducted. Three parameters are examined: (1) the inlet flow velocity, (2) heater temperature and (3) heat source location. Their effects on triggering limit cycle oscillations are first investigated in 2D numerical model. As each of the parameters is varied, the head-driven acoustic signature is found to change. The main nonlinearity is identified in the heat fluxes. To characterize the transient (growing) behavior of the pressure fluctuation, the thermoacoustic mode growth rate is defined and calculated. It is found that the growth rate decreases first and then ‘saturates’. Similar behavior is observed by examining the slope of Rayleigh index. Furthermore, the overall efficiency of converting the input thermal energy into acoustical energy is defined and calculated. It is found that the energy conversion efficiency can be increased by increasing the inlet flow velocity. To validate our numerical findings, a cylindrical T-shaped duct made of quartz-glass with a metal gauze attaching on top of a Bunsen burner is designed and tested. Supercritical bifurcation is observed. And the experimental measurements show a good agreement with the numerical results in terms of mode frequency, mode shape, sound pressure level and Hopf bifurcation behavior

[en] ABSTRACT: Spinel Li₄Ti₅O₁₂ has been thought as one of ideal anode materials for Li ion batteries due to its safety performance and long cycle life, while the low conductivity and Li-ion diffusion capability has limited its application. To improve the electrochemical performance of Li₄Ti₅O₁₂, Gd-doped single-crystalline Li₄Ti₅O₁₂/TiO₂ (rutile phase) nanosheets composites in this study was prepared via a solvothermal synthesis assisted method. It is found that the as prepared doped dual phases composites showed superior electrochemical performance as anode material. At a current density of 0.2 A/g (1.14 C), the Gd-LTO/TiO₂ electrode can deliver a specific capacity of ∼180.2 mAh/g, and it can deliver a specific capacity as high as ∼111.1 mAh/g even at current density of 20 A/g (114.3 C). The introduction of Gd ion has been found to play a crucial role in improving the electrochemical performance, and its introduction modifies the morphology of as prepared sample at the same time.

[en] Highlights: • Transient growth analysis of a thermoacoustic system is conducted. • A thermoacoustic model of a premixed flame is developed. • Four key parameters are identified and studied. • The flame-acoustics interaction can lead to transient energy growth. • The flame is discretized into distributed monopole-like sound sources. - Abstract: Transient growth of disturbances in a non-normal combustion system could trigger thermoacoustic instability. In this work, the effect of heat source on triggering thermoacoustic instability in a system with Dirichlet or Neumann boundary conditions is investigated. For this a thermoacoustic model of a premixed laminar flame is developed. It is formulated in state-space by expanding flow disturbances via Galerkin series and coupling with a flame model, thus providing a platform on which to gain insight on the system stability behaviors. Transient energy growth analysis is then performed by discretizing the flame model into distributed monopole-like sound sources. It is shown that the thermoacoustic system is non-normal and associated with transient energy growth. Parametric studies are then conducted to study the effects of (1) the flame-acoustics interaction index I, (2) the eigenmode number N, (3) the mean temperature ratio T between pre- and after-combustion regions on the system stability behavior and non-normality. It is found that the maximum transient energy growth G_max is increased with increased I. Furthermore, the thermoacoustic system with more eigenmodes is found to be associated with a larger G_max

[en] Highlights: • Cyclic indentation on a Cu-Zr metallic glass is conducted via molecular dynamics simulation. • The hardening behavior is more obvious with higher cyclic indentation amplitudes. • The hardening behavior becomes more severe at higher temperature due to the improvement of plasticity. • With lower loading rate, the shear bands are easily localized and the hardening phenomenon is less severe. - Abstract: Mechanical behavior of a Cu-Zr metallic glass (MG) under cyclic indentation loading is investigated via molecular dynamics simulation. A large-depth indentation after cycling is conducted, and the indentation curves show that hardening behavior occurs with cyclic indentation amplitudes exceeding elastic range. The atomic Von Mises shear strain distributions during the large-depth indentation are investigated, and the pre-existing plastic deformation induced by cyclic indentation is found to be the main contributor to the hardening behavior. By monitoring the atom trajectories and Voronoi atom volume, structure densification and free volume reduction phenomenon are found in the area beneath indenter after cycles. The accumulations of irreversible shear strain during cycling induce the area beneath indenter experience atom structure transition and become densified, thus the sample becomes more resistant to further deformation. In addition, the effects of temperatures and loading rates on the hardening behavior are studied. With higher temperature, more homogenous deformation and plasticity are produced, and then inducing more severe hardening in the MG. While with lower loading rate, the hardening phenomenon is found to be less severe because of the localization of shear strain during cycling.

[en] As a new detection model, the reversible fluorescence “turn-off-on” sensor based on quantum dots (QDs) has already been successfully employed in the detections of many biochemical materials, especially in the researches on the interactions between anticancer drugs. The previous studies, however, mainly focused on simple-structured oligonucleotides and Calf thymus DNA. G-quadruplex, an important target for anti-cancer drug with special secondary structure, has been stimulating increasing research interests. In this paper, we report a new detection method based on the fluorescence “turn-off-on” model with water-soluble ZnCdSe QDs as the fluorescent probe, to analyze the interactions between anticancer drug (N-methyl-4-pyridyl) porphyrin (TMPyP) and nucleic acid, especially the G-quadruplex. The fluorescence of QDs can be quenched by TMPyP via photo-induced electron transfer and fluorescence resonance energy transfer, while on the other hand, the combination between TMPyP and G-quadruplex releases QDs from their quenchers and thus recovers the fluorescence. Most importantly, the fluorescence “turn-off-on” model has been employed, for the first time, to analyze the impacts of special factors on the interaction between TMPyP and G-quadruplex. The excellent selectivity of the system has been verified in the studies of the interactions between TMPyP and different DNAs (double-stranded DNA, single-stranded G-quadruplex, and different types of G-quadruplexes) in Na"+ or K"+-containing buffer. - Highlights: • Reversible fluorescence sensor was firstly used on TMPyP and G-quadruplex study. • SsDNA and various G-quadruplexes were successfully recognized by fluorescence. • The new quantum dot is hypotoxicity and can be extensively applied

[en] Highlights: • An improved integration model is presented to describe the thermo-mechanical coupled behavior of FCC polycrystals. • The thermal tensile test of 22MnB5 boron steel in austenite region is performed. • Effects of temperature, strain rate and cooling rate on materials’ forming process are studied. - Abstract: An improved integration model based on crystal plasticity is presented to model the thermo-mechanical processes of face-centered-cubic (FCC) polycrystals. In this model, the thermal part of deformation gradient is introduced into the multiplicative decomposition of the total deformation gradient and the plastic deformation gradient is chosen as the basic integration variable. The effects of temperature, temperature changing rate and dissipation of plastic deformation are considered in the finite deformation computation. The obtained plastic deformation gradient includes the plastic deformation as well as the thermal effects. In applications, the mechanical behaviors of 1100 Al in warm forming and 22MnB5 boron steel in hot tensile deformation were computed using this model. In experiments, the hot tensile tests of 22MnB5 boron steel were performed in the isothermal and non-isothermal conditions. The predicted results can reflect the thermal effects in forming process and agree well with the experimental data

[en] High-quality water-soluble Mn²⁺ doped CdTe quantum dots (QDs) with N-acetyl-L-cysteine (NAC) as capping reagent have been synthesized through hydrothermal route, allowing a rapid preparation time (<1 h), tunable emitting peaks (from 530 to 646 nm) and excellent quantum yields (approximately 50%). The influences of various experimental variables, including Mn-to-Cd ratio, Te-to-Cd ratio, pH value, and reaction time on the growth rate and luminescent properties of the obtained QDs have been systematically investigated. And the optimum reaction conditions (Cd:Mn:NAC:Te=1.0:1.0:2.4:0.2, pH=9.5, 35 min, 200 °C) are found out. The optical features and structure of the obtained CdMnTe QDs have been characterized through fluorescence spectroscopy, UV absorption spectroscopy and TEM. In particular, we realized qualitative, semi-quantitative and quantitative studies on the doping of Mn to CdTe QDs through XPS, EDS, and AAS. The actual molar ratio of Mn to Cd in CdMnTe QDs (551 nm) is 1.166:1.00, very close to the feed ratios (1:1). - Highlights: • Mn doped CdTe QDs have been synthesized through one-pot hydrothermal route. • The prepared QDs possess excellent quantum yields as high as 63.1% and tunable emitting peaks from 530 to 646 nm. • We found out that the enhancement of Mn:Cd will decrease the QY of the prepared QDs and lead to the blueshift of emission peaks. • The QDs have been characterized through TEM, EDS, XPS, and AAS

[en] Efficient and non-Pt catalysts are highly desirable for many kinds of electrochemical applications. Herein, we have investigated the free-standing nitrogen-doped carbon nanotubes/carbon nanofibers composite (NCNT/CNFs) as an efficient cathode catalyst for the oxygen reduction reaction (ORR). The composite with a hierarchical structure is prepared by the pyrolysis of pyridine over flexible electrospun carbon nanofibers film (CNFs) supported with the nano-Fe catalyst. Scanning electron microscopy and transmission electron microscopy characterizations indicated that the curved NCNTs are sparsely, but tightly distributed on CNF surface. The as-prepared composite displayed good catalytic activity for ORR in an alkaline medium, with a favorable four-electron pathway, better long-term stability (94.6% retention after 10000 s), selectivity and resistance to the methanol crossover compared to the powder-form NCNTs and commercial Pt/C catalyst. The improved electrochemical performance of the NCNT/CNFs can be mainly attributed to the pyridinic-N doping and unique three-dimensional network structure. The results indicate that this novel composite can be used as a promising Pt-free ORR electrocatalyst

[en] Highlights: • Bi_4Ti_3O_1_2/SrTiO_3 composite was fabricated by combining hydrothermal reaction and molten salt method. • Bi_4Ti_3O_1_2/SrTiO_3 exhibits higher photocatalytic activity than pure Bi_4Ti_3O_1_2. • The absorption light of Bi_4Ti_3O_1_2/SrTiO_3 has been broadened to visible light. - Abstract: In this study, Bi_4Ti_3O_1_2/SrTiO_3 micro-platelets were successfully synthesized by using hydrothermal and molten salt methods, and the morphology and photocatalytic degradation performance of Bi_4Ti_3O_1_2/SrTiO_3 was characterized. The results indicated a much higher degradation rate of methylene blue and methylene orange, reaching more than 90% and 65%, respectively, within 3 h under visible-light irradiation. Compared with pure Bi_4Ti_3O_1_2, the photocatalytic activity of Bi_4Ti_3O_1_2/SrTiO_3 was significantly better, due to the micron–submicron heterojunction with SrTiO_3 reducing the band gap of Bi_4Ti_3O_1_2. In addition, the perovskite structure layer facilitates the mobility of the photogenerated carriers and hampers their recombination, which were affected the photocatalytic properties

[en] During ¹³¹I therapy or the natural course of DTC, 2% to 5% of them will gradually no longer be sensitive to ¹³¹I therapy and lead to radioactive iodine-refractory DTC (RAIR-DTC). Recent studies found that alterations of critical molecular targets in main signal transduction pathways could decrease the iodine-trapping function of thyroid carcinoma, such as BRAF^V600E mutation, followed by negative ¹³¹I-whole body scan (WBS) and discounted efficacy. This article reviews novel diagnostic and therapeutic modalities for RAIR-DTC. (authors)