We designed a stream-cipher algorithm based on one-time keys and robust chaotic maps, in order to get high security and improve the dynamical degradation. We utilized the piecewise linear chaotic map ...as the generator of a pseudo-random key stream sequence. The initial conditions were generated by the true random number generators, the MD5 of the mouse positions. We applied the algorithm to encrypt the color image, and got the satisfactory level security by two measures: NPCR and UACI. When the collision of MD5 had been found, we combined the algorithm with the traditional cycle encryption to ensure higher security. The ciphered image is robust against noise, and makes known attack unfeasible. It is suitable for application in color image encryption.
Molecular dynamics simulations have been performed to investigate the structure and dynamics of the ionic liquid, 1-n-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C(4)mimTf(2)N) in ...the temperature range of 283-460 K. Extensive analysis was carried out to characterize a number of structural and dynamic features. Transport properties were computed using a variety of equilibrium methods that employed the Green-Kubo and Einstein formulations. Nonequilibrium techniques were also used. In general, different methods mostly yielded consistent results, although some differences were observed. Computed self-diffusivities and ionic conductivities tended to be slightly lower than experimental values, while computed viscosities were significantly higher than experiment. Computed thermal conductivities agreed reasonably well with experimental data. Despite these discrepancies, the simulations capture the experimental temperature-dependent trends for all these transport properties. Single ion dynamics were studied by examining diffusional anisotropy, the self-part of the van Hove function, non-Gaussian parameters, and incoherent intermediate scattering functions. It is found that cations diffuse faster than anions and are more dynamically heterogeneous. A clear anisotropy is revealed in cation displacement, with the motion normal to the imidazolium ring plane being the most hindered and the motion along the alkyl chain in the plane of the ring being the most facile. Cations structurally relax faster than anions but they rotationally relax slower than anions. There is a pronounced temperature dependence to the rotational anisotropy of the cations, but only a weak temperature dependence for the anions. The ionic conductivity deviates from the Nernst-Einstein relation due to the correlated motion of cations and anions. The results suggest that the dynamical behavior of this and related ionic liquids is extremely complex and consists of many different modes with widely varying timescales, making the prediction of dynamical trends extremely difficult.
The modified hydrochar was prepared by a facile one-pot lime-assisted hydrothermal synthesis approach and the modified hydrochar and pristine hydrochar were investigated to immobilize the heavy ...metals (HMs) of Pb and Cd in contaminated soils. The results showed that the modified hydrochar exerted significantly enhanced effectiveness in immobilizing Pb and Cd comparing to pristine hydrochar, resulting from the increased surface functionality and non-crystalline properties, increased pH value and enhanced electronegativity of hydrochar. By introduction with 5% modified hydrochar, the contaminated soils showed the highest value of 34.5% (Pb) and 8.1% (Cd) reductions in leaching toxicity, and significant improvements of 95.1% (Pb) and 64.4% (Cd) were observed. In addition, the concentrations of acid soluble fraction were remarkably reduced by 54.0% (Pb) and 27.0% (Cd), and the reductions were much higher than that of 29.5% (Pb) and 8.3% (Cd) for 5% pristine hydrochar treatment. The enhanced surface complexation, precipitation and cation-π interaction played an important role in the immobilization of HMs in soils. The present study offered a novel and cost-effective approach to prepare soil amendment from waste biomass towards HMs immobilization in contaminated soils.
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•The modified hydrochar was prepared by a facile one-pot lime-assisted hydrothermal method.•Modified hydrochar had increased surface functionality, non-crystalline property and pH value.•Modified hydrochar showed significantly increased capacity for metal immobilization.•Modified hydrochar could be served as a novel cost-effective soil amendment.
Abstract
High-quality two-dimensional atomic layered p–n heterostructures are essential for high-performance integrated optoelectronics. The studies to date have been largely limited to exfoliated ...and restacked flakes, and the controlled growth of such heterostructures remains a significant challenge. Here we report the direct van der Waals epitaxial growth of large-scale WSe
2
/SnS
2
vertical bilayer p–n junctions on SiO
2
/Si substrates, with the lateral sizes reaching up to millimeter scale. Multi-electrode field-effect transistors have been integrated on a single heterostructure bilayer. Electrical transport measurements indicate that the field-effect transistors of the junction show an ultra-low off-state leakage current of 10
−14
A and a highest on–off ratio of up to 10
7
. Optoelectronic characterizations show prominent photoresponse, with a fast response time of 500 μs, faster than all the directly grown vertical 2D heterostructures. The direct growth of high-quality van der Waals junctions marks an important step toward high-performance integrated optoelectronic devices and systems.
Van der Waals (vdW) heterostructures are the fundamental blocks for two-dimensional (2D) electronic and optoelectronic devices. In this work, a high-quality 2D metal–semiconductor NiTe2/MoS2 ...heterostructure is prepared by a two-step chemical vapor deposition (CVD) growth. The back-gated field-effect transistors (FETs) and photodetectors based on the heterostructure show enhanced electronic and optoelectronic performance than that of a pristine MoS2 monolayer, owing to the better heterointerface in the former device. Especially, this photodetector based on the metal–semiconductor heterostructure shows 3 orders faster rise time and decay time than that of the pristine MoS2 under the same fabrication procedure. The enhancement of electronic behavior and optoelectronic response by the epitaxial growth of metallic vdW layered materials can provide a new method to improve the performance of optoelectronic devices.
Reported is the controllable selectivity syntheses of four distinct products from the same starting materials by visible‐light photoredox catalysis. By employing a dicyanopyrazine‐derived chromophore ...(DPZ) as photoredox catalyst, an aerobic radical mechanism has been developed, and allows the reactions of N‐tetrahydroisoquinolines (THIQs) with N‐itaconimides to through four different pathways, including addition‐cyclization, addition‐elimination, addition‐coupling, and addition‐protonation, with satisfactory chemoselectivity. The current strategy provide straightforward access to four different but valuable N‐heterocyclic adducts in moderate to excellent yields.
Radical control: A radical mechanism for N‐tetrahydroisoquinolines (THIQ) in the presence of oxygen was successfully accomplished by employing a dicyanopyrazine‐derived chromophore (DPZ) as a photoredox catalyst. The substrates can undergo either addition‐cyclization, addition‐elimination, addition‐coupling, or addition‐protonation by judiciously regulating the reaction conditions. Four types of N‐heterocycles are generated in moderate to excellent yields.
Heart failure (HF) and atrial fibrillation (AF) are often coexisting. They have common risk factors and pathophysiologic mechanisms. Sacubitril/valsartan has shown efficacy and tolerability in ...patients with HF. Thus, the study was performed to evaluate the impact of sacubitril/valsartan on AF occurrence in patients with HF.
The Embase and PubMed were searched from their inception date to June 2021 for all relevant randomized controlled trials (RCTs) evaluating the efficacy of sacubitril/valsartan in HF. The outcome of interest was the AF occurrence during the follow-up. Relative risks (RRs) with 95% confidence intervals (CIs) were pooled using a random-effects model.
Six trials involving a total of 15,512 patients were included (7,750 randomized to sacubitril/valsartan and 7,762 to control). All trials were randomized, double-blind, and active-control. There was no significant difference in the prevention of AF occurrence between the sacubitril/valsartan group and the control group (enalapril or valsartan) in patients with HF (RR 1.07, 95%CI 0.95 to 1.19; I2 4%).
Sacubitril/valsartan was similar to either enalapril or valsartan in preventing the occurrence of AF in patients with HF.
As an important mid-infrared to far-infrared optical window, ZnS is extremely important to improve spectral transmission performance, especially in the military field. However, on account of the ...Fresnel reflection at the interface between the air and the high-strength substrate, surface optical loss occurs in the ZnS optical window. In this study, the concave antireflective sub-wavelength structures (ASS) on ZnS have been experimentally investigated to obtain high transmittance in the far-infrared spectral range from 6 μm to 10 μm. We proposed a simple method to fabricate microhole array ASS by femtosecond Bessel beam, which further increased the depth of the microholes and suppressed the thermal effects effectively, including the crack and recast layer of the microhole. The influence of different Gaussian and Bessel beam parameters on the microhole morphology were explored, and three ASS structures with different periods were prepared by the optimized Bessel parameters. Ultimately, the average transmittance of the sample with the ASS microhole array period of 2.6 μm increased by 4.1% in the 6 μm to 10 μm waveband, and the transmittance was increased by 5.7% at wavelength of 7.2 μm.
The rheological property plays an important role in a free-form extrusion 3D printing process, no rheological model was available in open literature that could effectively take into account effects ...of both the non-Newtonian viscosity and the concentration of nano/micro particles in a paste. Here a fractal law for non-Newtonian fluids is suggested using a fractal derivative, the law can predict correctly the boundary effect of a viscous flow, and can model effectively the nonlinear velocity distribution across the section. A systematic derivation of a fractal rheological model is suggested using the basic laws in the fluid mechanics, which can provide a deep insight into the two-scale fractal interpretation of non-Newtonian fluids. An experiment was carefully designed to verify the model and to elucidate the relationship between the shear rate and viscosity of the SiC paste. 15wt.%, 25wt.%, 35wt.% and 45wt.% SiC pastes were prepared by using mixing, stirring and ball milling processes. The rheology of the paste can be controlled primarily through the SiC concentration, which affects the fractal order. The fractal model sheds a bright light on a simple but accurate approach to non-Newtonian fluids.
Here is a proposal of lossless dual-channel audio encryption scheme based on one-time keys, the novelty is to apply chaotic system with changeable multi-scroll to generate key stream to confuse and ...diffuse audio data, and the one-time keys, such as initial values of state variables, scroll number and initial iteration times of the chaotic system, are dependent on both external keys and hash value of the plain audio file, to make the chaotic trajectory more unpredictable. The algorithm owns large key space to make brute-force attack impossible. Statistical analysis demonstrates the effectiveness for fast audio encryption, and the scheme can also be applied in encrypting audio with more channels.
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