We propose a new image encryption algorithm based on the spatiotemporal chaos of the mixed linear–nonlinear coupled map lattices. This spatiotemporal chaotic system has more outstanding cryptography ...features in dynamics than the logistic map or the system of coupled map lattices does. In the proposed image encryption, we employ the strategy of bit-level pixel permutation which enables the lower bit planes and higher bit planes of pixels permute mutually without any extra storage space. Simulations have been carried out and the results demonstrate the superior security and high efficiency of the proposed algorithm.
•We propose an image encryption scheme based on a new spatiotemporal chaotic system.•The encryption scheme is not the one time pad encryption.•The proposed image encryption has a large key space and ...high security.
We propose a new image encryption algorithm which is based on the spatiotemporal non-adjacent coupled map lattices. The system of non-adjacent coupled map lattices has more outstanding cryptography features in dynamics than the logistic map or coupled map lattices does. In the proposed image encryption, we employ a bit-level pixel permutation strategy which enables bit planes of pixels permute mutually without any extra storage space. Simulations have been carried out and the results demonstrate the superior security and high efficiency of the proposed algorithm.
We investigate the strong deflection gravitational lensing by an Einstein–Lovelock ultracompact object. Its unique features are the relativistic images inside its photon sphere which are absent for ...an Einstein–Lovelock black hole. We obtain its lensing observables and evaluate their observability for the direct images of two supermassive black holes in the Galaxy and M87 respectively, Sgr A* and M87*, and for the relativistic microlensing on a star closely around Sgr A*. We find that although it is impossible to tell difference of the ultracompact object from the black hole in Einstein–Lovelock gravity by the direct images, it might be possible to distinguish the Einstein–Lovelock ultracompact object by measuring the total flux of the relativistic microlensing in the not-so-far future.
•Fate of heavy metals during the hydrothermal treatment of sewage sludge.•Assessment indices of the contamination level and ecological risk of heavy metals.•The effect of reaction temperature and ...reaction time.•The effect of the addition of catalyst/other biomass.•The effect of the type of liquefaction solvent.
Various hydrothermal treatment methods, including hydrothermal carbonization, liquefaction and sub/super-critical water gasification, have been applied to the disposal of sewage sludge for producing bio-materials or bio-fuels. It has become a research hotspot whether the heavy metals contained in sewage sludge can be well treated/stabilized after the hydrothermal treatments. This review firstly summarized the methods of assessing heavy metals’ contamination level/risk and then discussed the migration and transformation behaviors of heavy metals from the following aspects: the effect of reaction temperature, the effect of additives (catalysts and other biomass), the effect of the type of solvent and the effect of reaction time. This review can provide an important reference for the further study of the migration and transformation behaviors of heavy metals during the hydrothermal treatment of sewage sludge.
Background
Pancreaticoduodenectomy (PD) is one of the most technically difficult abdominal operations. Recent advances have allowed surgeons to attempt PD using minimally invasive surgery techniques. ...This retrospective study aimed to analyze the learning curve of a single surgeon who had carried out his first 100 robot-assisted laparoscopic pancreaticoduodenectomy (RPD) in a high-volume pancreatic center.
Methods
The data on consecutive patients who underwent RPD for malignant or benign pathologies were prospectively collected and retrospectively analyzed. The data included the demographic data, operative time, estimated blood loss, postoperative length of hospital stay, morbidity rate, mortality rate, and final pathological results. The cumulative sum (CUSUM) analysis was used to identify the inflexion points which corresponded to the learning curve.
Results
Between 2012 and 2016, 100 patients underwent RPD by a single surgeon. From the CUSUM operation time (CUSUM OT) learning curve, two distinct phases of the learning process were identified (early 40 patients and late 60 patients). The operation time (mean, 418 min vs. 317 min), hospital stay (mean, 22 days vs. 15 days), and estimated blood loss (mean, 227 ml vs. 134 ml) were significantly lower after the first 40 patients (
P
< 0.05). The pancreatic fistula, postoperative hemorrhage, delayed gastric emptying, and reoperation rates also decreased in the late 60 patients group (
P
< 0.05). Non-significant reductions were observed in the incidences of major (Clavien–Dindo Grade II or higher) morbidity, postoperative death, bile leakage, gastric fistula, wound infection, and open conversion.
Conclusions
RPD was technically feasible and safe in selected patients. The learning curve was completed after 40 RPD. Further studies are required to confirm the long-term oncological outcomes of RPD.
Microplastics (MPs), the appearance of which has gained considerable interest, can act as vectors to transport other pollutants such as metals into organisms. In this study, the sorption isotherms of ...three model heavy metals (i.e., Cu2+, Cd2+, and Pb2+) on four virgin plastic particles including chlorinated polyethylene (CPE), PVC, and two polyethylene plastic particles (i.e., LPE and HPE). HPE and LPE were investigated. The results showed that MPs can load high amounts of Pb2+, Cu2+ and Cd2+. The sorption affinity of the three metals to the model MPs followed the sequence of CPE > PVC > HPE > LPE. The adsorption process was affected by the chemical structure and electronegativity of the sorbents, and seemed irrelevant to the crystallinity of MPs. For the three metals, Pb2+ exhibited significantly stronger sorption than did Cu2+ and Cd2+ due to the strong electrostatic interaction. Moreover, pH can significantly affect the sorption of metals on MPs, but ionic strength exerted a relatively slight effect on this process. In brief, the electrostatic interaction played an important role in the sorption of Pb2+ to model MPs. For Cd2+ and Cu2+, sorption was determined by electrostatic interaction together with surface complexation onto the plastic surface. This study indicates that depending on the surface physicochemical properties of MPs the adsorption behavior can vary significantly. Therefore, the adsorption process of metals on MPs should be readily affected by other environmental mediums in the environment. The study provides additional insight into the behavior of MPs as a vector of metals.
•Sorption of Cu2+, Cd2+, and Pb2+ on four virgin plastic particles was investigated.•The sorption strength followed the order of Pb2+>Cu2+>Cd2+.•PH and ionic strength can affect the sorption of metals on MPs.•Electrostatic interaction played an important role in the sorption of Pb2+ to MPs.•Electrostatic interaction and complexation determined the sorption of Cd2+ and Cu2+.
Yangtze River basin (YZB) experienced record‐breaking heat in the summer of 2022. Here, we focused on daytime‐nighttime compound heat waves, and used the magnitude index that considers both duration ...and intensity to investigate the risk of the 2022 extreme heat. The magnitude of heatwaves in 2022 was much larger than the historical average level, which was estimated as a 1‐in‐64‐year event over 1979–2014 climate. Without mitigation efforts (SSP585), the record‐breaking heat would emerge as normal during 2050s, and would affect ∼70% of land and projected population in the basin before global mean temperature change reaches 3°C. Such an emergence could be progressively delayed and impacts could be reduced under lower warming levels. The affected area would be 60% lesser at 2°C warming, and the emergence could be avoided by limiting warming to 1.5°C. Our results call for urgent mitigation efforts for reducing the risk of compound heat extremes.
Plain Language Summary
Persistent extreme high temperature occurred in Yangtze River basin (YZB) during summer 2022, leading to widespread droughts, heat‐related disease and socioeconomic losses. The physical drivers and future risk of the heat extremes have attracted extensive attention. Focusing on daytime‐nighttime compound heat waves, which have more adverse effect on human health and ecosystem, we investigated the magnitude of compound heat waves occurred in 2022, and future risk under different warming levels and emission scenarios. Observations show that the magnitude was the strongest since records began in 1979, and the return period was 64 (95% CI: 30–223) years over the 1979–2014 climate. Projections show that such unprecedented heat in observed records would emerge as normal since 2053 (2081) under nonmitigation (moderate mitigation) scenario. Moderate climate mitigation efforts could delay the time by 28 years. Compared with the 2°C global warming level, about 10% of lands and population would be avoided to normally expose to such heat at 1.5°C warming level. However, the exposures would increase by 60% from 2°C to 3°C warming level. This study suggests that mitigation actions for accomplishing 2°C warming goal and further pursuing the ambitious goal of 1.5°C can substantially reduce the exposure risk of such unprecedented heat.
Key Points
The 2022 record‐breaking compound heat waves in Yangtze River basin would become normal during 2050s under a nonmitigation scenario
Moderate climate mitigation efforts would delay the time of emergence by 28 years
Compared to 3°C, limiting warming to 2°C and 1.5°C could avoid 60% and 70% of lands that are normally affected by such rare heat, respectively
•A new color image encryption scheme is proposed based on the spatiotemporal chaos of the two dimensional nonlinear coupled map lattices (2DNLCML) and genetic operations.•Due to the spatial nonlinear ...coupling, this 2DNLCML system can generate superior pseudo-random sequences for image encryption.•The scheme employs genetic operations followed by mutation and crossover operation using binary encoding, which consumes a low amount of computational cost.•Simulation results indicate that the proposed scheme has a good encryption effect and can resist various typical attacks.
Based on the spatiotemporal chaos of the two Dimensional Nonlinear Coupled Map Lattices (2DNLCML) and genetic operations, a new optical color image encryption scheme is proposed. Because of the spatial nonlinear coupling which replaces traditional adjacent coupling, the 2DNLCML system contains good features such as ergodic pseudo-random sequence, less periodic windows in bifurcations and larger range of parameters in chaotic dynamics, which is more suitable for image encryption. The scheme also performs genetic operations including mutation and crossover for binary coding, thus reducing the computational complexity. Simulations have been carried out and the results demonstrate that the proposed algorithm has properties of large key space, high sensitivity to key, strong resisting attack. So, it is more secure and effective algorithm for encryption of digital images.
In this study, a sensitive infrared photodetector (IRPD) composed of a germanium nanocones (GeNCs) array and PdSe2 multilayer is presented, which is obtained by a straightforward selenization ...approach. The as‐assembled PdSe2/GeNCs hybrid heterojunction exhibits obvious photovoltaic behavior to 1550 nm illumination, which renders the IRPD a self‐driven device without external power supply. Further device analysis reveals that the PdSe2/GeNCs hybrid based IRPD exhibits high sensitivity to 1350, 1550, and 1650 nm illumination with excellent stability and reproducibility. The responsivity and external quantum efficiency is as high as 530.2 mA W−1 and 42.4%, respectively. Such a relatively good device performance is related to the strong light trapping effect of GeNCs array, according to the theoretical simulation based on finite‐difference time‐domain. It is also found that the IRPD shows an abnormal sensitivity to IR illumination with a wavelength of 2200 nm. Finally, the present individual IRPD can also record the simple “F” image produced by 1550 nm, suggesting the promising application of the PdSe2/GeNCs hybrid device in future infrared optoelectronic systems.
A highly sensitive infrared light photo‐detector is fabricated by transferring multilayer PdSe2 on a germanium nanocones array with a strong light‐trapping effect. The as‐assembled PdSe2/GeNCs hybrid heterojunction devices can also record simple near‐infrared images.
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