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Optical regulation strategy with the aid of hybrid materials can significantly optimize the performance of terahertz devices. Gold nanobipyramids (AuNBPs) with synthetical tunability to the near-infrared band show strong local field enhancement, which improves optical coupling at the interface and benefits the modulation performance. We design AuNBPs-integrated terahertz modulators with multiple structured surfaces and demonstrate that introducing AuNBPs can effectively enhance their modulation depths. In particular, an ultrahigh modulation enhancement of 1 order of magnitude can be achieved in the AuNBPs hybrid metamaterials accompanied by the multifunctional modulation characteristics. By application of the coupled Lorentz oscillator model, the theoretical calculation suggests that the optical regulation with AuNBPs originates from increased damping rate and higher coupling coefficient under pump excitation. Additionally, a terahertz spatial light modulator is constructed to demonstrate multiple imaging display and consume extremely low power, which is promising for the potential application in spatial and frequency selective imaging.

A DIPEA–NHPI ester–inorganic carbonate catalytic EDA complex is reported as an efficient and sustainable radical generation platform for developing photocatalytic reactions.

Enamel regeneration currently -is limited by our inability to duplicate artificially its complicated and well-aligned hydroxyapatite structure. The initial formation of enamel occurs in enamel organs where the ameloblasts secret enamel extracellular matrix formed a unique gel-like microenvironment. The enamel extracellular matrix is mainly composed by amelogenin and non-amelogenin. In this study, an innovative strategy was proposed to regenerate enamel-like tissue by constructing a microenvironment using biomimetic enamel matrix proteins (biomimetic EMPs) composed of modified leucine-rich amelogenin peptide (mLRAP) and non-amelogenin analog (NAA). Impressively, the regenerated enamel in this biomimetic EMPs on etched enamel surface produced prismatic structures, and showed similar mechanical properties to natural enamel. The results of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that regenerated crystal was hydroxyapatite. Molecular dynamics simulation analysis showed the binding energy between mLRAP and NAA were electrostatic forces and Van der Walls. These results introduced a promising strategy to induce crystal growth of enamel-like hydroxyapatite for biomimetic reproduction of materials with complicated hierarchical microstructures.

Due to the structural constraints, mandatory volumetric examination is not implemented on small branch BOSS joints of nuclear power plant, which leads to internal defects cannot be detected thoroughly, causing potential risk to the safe and stable operation. Key factors affecting the welding quality of small branch BOSS joints are systematically analyzed in this paper. Besides, practical suggestions are provided on the operating level to improve the welding quality, including groove design, welding process, welder qualification and nondestructive examination. On this basis, further improvement suggestions are proposed to revise the codes and regulatory guides.

The management of

The development of electrocatalysts with high activity is essential to convbar glycerol into value-added chemicals through electrocatalytic oxidation. Nano-sized metals with prickly structures are expected to possess high electrocatalytic activity due to the strong electric field at the sharp tips. We propose a facile approach to prepare Au nanoparticles with prickly structure by galvanic displacement in this work. The reaction between Au3+ and Ni generates in situ highly dispersed Au nanoparticles with prickly structures on the Ni foam. Owing to appropriate prickly structure, the Au nanoparticles prepared at 25∘C for 30 s exhibited the best electrocatalytic performance. Finite element simulation method simulations show that the high-density of positive charge at the tips forms strong electric field, which enriches OH− ions and promotes glycerol oxidation, thus exhibiting excellent electrocatalytic activity. This study will guide further design/development of electrocatalytic nanostructured Au particles and provide an effective route to electrocatalytically oxidize glycerol.

A terahertz hybrid metamaterial incorporated with active media VO2 holds great promise for the realization of a new generation of reconfigurable and multifunctional devices. However, for the electrical control, many efforts on reducing high working threshold are usually based on the utilization of patterned VO2 patches or additional insulation layers, which will increase the complexity of the fabrication procedure. Here, we have proposed an effective strategy only by combining the surface microstructure and the unpatterned VO2 film to realize the tunability of working current and uncover its highly dependent correlation with the structural resonance responses. It is shown the fully modulated current in our hybrid metastructures can be reduced with the prominently separated hysteresis loops. Further developed binary encoders can perform not only the information transformation of the fixed code symbols but also the arbitrary encoding with the programmable current pulse. Additionally, the dynamic color display can be accomplished to illustrate the intriguing function of the information encryption and multi-image reappearance with the current as the decryption key. Our work provides an approach to reduce the operating current and paves a pathway for the development of photonic memory information processors.

Metamaterials are artificial materials with unique electromagnetic properties and could exhibit a strong electromagnetic resonance. Resonant metamaterials are widely used in the field of biosensors because they are sensitive to the changes of surface dielectric environment. In this study, we demonstrated a highly sensitive detection method of 4-Mercaptohydrocinnamic acid using terahertz metamaterials fabricated on silicon substrate with metal arrays of the three bars structure. We measured the transmission spectra of the metamaterial to detect the 4-Mercaptohydrocinnamic acid at three different densities by the terahertz time-domain spectroscopy system. With the density of 4-Mercaptohydrocinnamic acid increasing, resonance dips exhibit the red-shift phenomena and transmission at the resonance frequency simultaneously reduce. The movement of resonance dips and the change of transmission show that the three bars resonators are sensitive to the density of analyte. The finite-difference time-domain simulation shows a good agreement with the experimental data, and the simulation of surface current and electric field distributions at resonance dips can further understand the resonance modes in transmission spectra. Our study provides new prospect into the application of terahertz metamaterials in biosensing.

We modulate the electromagnetic response of terahertz metamaterials by exciting photogenerated carriers with ultra-short pulsed laser, and realize the active control of terahertz transmission and resonances in a wide band. The experimental results show that when the terahertz electric vector is perpendicular and parallel to the bar direction with the open gap in the circular split ring resonators, respectively, the transmission of the non-resonant region and resonance absorption are significantly tuned by the irradiated pump pulse. With the increase of the pump power, the resonance absorption peak decreases and the frequency of resonance dip has a remarkable blue-shift. Meanwhile, the transmission of the non-resonant region decreases correspondingly. It is also found that the blue-shift of the resonance is mainly determined by the change of conductivity and dielectric constant in the photoexcited layer of the substrate. Through the numerical simulation, we have further proved the introduction of pump light has a significant modulation effect on the electromagnetic properties of terahertz metamaterials. Additionally, it can be observed that the LC resonance annihilates earlier than the resonance of the dipole resonance with the increase of pump power, implying the former is particularly sensitive to the variation of the active control. In the theoretical analysis, based on the Lorenz oscillator model, we have derived and calculated the resonance response intensity of the coupled oscillators under an external field. The calculated results indicate the coupling coefficient and damping rate have an impact on the spectra evolution, showing that the resonant response peak has a remarkable blue-shift with the increase of coupling coefficient and the resonance response intensity decreases with the increase of damping rate.

Highly sensitive response of anisotropic terahertz metamaterials to electromagnetic waves has attracted considerable attention due to its potential applications in terahertz modulators and biosensing devices. We designed three microstructure samples with split ring arrays. The terahertz transmission spectra are experimentally measured at different rotation angle. It is found that as the rotation angle increases, the resonance mode has gradually evolved from a single dipole oscillation mode to the double oscillation modes accompanied with LC and dipole oscillations, we further simulated the polarization conversion characteristics of the single splitting rings. It shows that the highest conversion efficiency appears at 45 degrees. But it doesn’t have polarization conversion effect at 0° and 90°. Subsequently, we have utilized ultrashort pulse laser to optically control the electromagnetic response by exciting the photogenerated carriers in the metamaterial samples. The experimental data show that the transmittance change obviously with the pump light. Additionally, when the angle is 90 degrees, it can be observed that the LC resonance annihilates earlier than the resonance of the dipole resonance with the increase of pump power, implying the former is particularly sensitive to the variation of the dielectric environment. To further explore the influence of dielectric environment on the resonance characteristics of the terahertz metamaterials, we have further performed the simulations with the applied surface analyte of different refractive index. The simulated data show that with the increase of the refractive index of the surface analyte, the resonance frequency of the dipole oscillation has a more significant blue shift than the resonance frequency of the LC oscillation. Our obtained results could provide the idea for designing terahertz modulators and sensitive biosensing devices.

Metamaterials has shown outstanding flexibility and functionality in optics and electromagnetics, which attracted plenty of interest. Nested ring resonators have a wide range of applications in terahertz (THz) spectroscopy, sensing and communication. Hence, we design a kind of metamaterials structure which can modulate THz transmission and resonance. It consists of a circular split ring resonator (CSRR) inside a closed square ring resonator. The single CSRR has an inductive-capacitive (LC) resonance and the single closed square ring resonator has a dipole resonance. After nesting two resonators, the resonance mode is changed from single mode to double modes. The results show that the amplitude transmission of non-resonant region is related to the gap opening and the asymmetry of structure. The amplitude transmission of resonance region depends on the conductivity of substrate. With the gap opening of CSRR increases, the amplitude transmission of non-resonant region increase. Meanwhile, the frequency of resonance has an obvious blue-shift. With the bottom edge distance of the two resonators decreases(the asymmetry increases), the amplitude transmission of the non-resonant region increases gradually and the low frequency of resonance has a red-shift and the high frequency of resonance has a blue-shift. To further analyze the influence of conductivity of substrate on amplitude transmission, we change the conductivity of substrate during the simulation. The results demonstrate that with the conductivity of the substrate increases, the resonance absorption peak decreases until disappears, the amplitude transmission of the non-resonant region decreases. Our results may have the potential applications in THz modulator.

With strong optical response from subwavelength metamaterial structures in terahertz, plasmon-induced transparency (PIT) has attracted considerable attention in terahertz modulators and biosensing devices. Here, we tune PIT effect by the destructive interference of two bright modes. We design a terahertz metamaterials structure with triple U-shaped resonators (TUR) arrays. In the vertical direction, double U-shaped resonators (DUR) are arranged downward, single-U resonator (SUR) is upward. We change the length of the SUR, the inner arms of the DUR and the horizontal distance of the DUR in order to observe the terahertz transmission spectrum. It is found from the results that with the length of the SUR increases， the resonant frequency has an obvious red-shift, the absorption of the low-frequency resonance increases and the nonresonance absorption peak gradually decreases. As the arms of the DUR increase and the distance between them decreases in horizontal, the frequency of resonance dip has a red-shift, and the transmittance of the non-resonant region increases slightly. To explore the influence of dielectric environment on the resonance characteristics of the terahertz metamaterials, we have further performed the simulations with the applied surface analyte of different refractive index. The results show that with the increase of the refractive index of the surface of the analyte, the resonance frequency has a more significant red-shift. Our obtained results could provide the idea for designing terahertz modulators and sensitive biosensing devices.

In the quest for emerging in-sensor computing, materials that respond to optical stimuli in conjunction with non-volatile phase transition are highly desired for realizing bioinspired neuromorphic vision components. Here, we report a non-volatile multi-level control of VO

We experimentally and numerically demonstrate resonant behaviors of terahertz metamaterials can be tuned significantly by their asymmetry. For the ring structure cut symmetrically, transmission spectra are nearly the same as those of their individual single-ring resonators. However, three resonant dips appear in the spectra due to the broken symmetry in single-ring resonator cut asymmetrically from the top. For the asymmetrically-cut double-ring structures, the mutual coupling between four arcs results in multi-resonance dips, especially a low-frequency Fano-like resonance accompanied with a sharp peak. Our asymmetric structures could offer potential applications in terahertz frequency selectors and bio-sensors.

Chronic constipation is a common gastrointestinal dysfunction, but its aetiology and pathogenesis are still unclear. Interestingly, the compositions of the gut microbiota in constipation patients and healthy controls are different. Various studies reported the different gut microbiota alterations in constipation patients, but most studies indicated that constipation patients showed the decreased beneficial bacteria and the reduced species richness of gut bacteria. Besides, the alterations in the gut microbiota may lead to constipation and constipation-related symptoms and the regulation of gut microbiota has a positive effect on gut functional diseases such as constipation. Microbial treatment methods, such as probiotics, prebiotics, synbiotics, and fecal microbiota transplantation, can be used to regulate gut microbiota. Increasing evidences have suggested that Chinese medicine (CM) has a good therapeutic effect on chronic constipation. Chinese medicine is well known for its multitarget and multimode effects on diseases as well as less side effects. In previous studies, after the treatment of constipation with CM, the gut microbiota was restored, indicating that the gut microbiota might be the target or important way for CM to exert its efficacy. In this review, we summarized the effects of microbial treatment and CM on the gut microbiota of constipation patients and discussed the relationship between CM and gut microbiota.

A hospital building features a number of different functional areas. The equipment and systems that serve the building and its medical needs are complex and require various forms of energy, including electricity, gas, steam, hot water and chilled water. Domestic and foreign research data show that the energy consumption per unit area of hospital buildings is twice that of general public buildings. This article selects a typical comprehensive hospital in the hot summer and cold winter area as a case, analyzes the actual energy demand of the hospital building through the measured data, and puts forward reasonable suggestions on the energy consumption mode and system improvement plan of the hospital in combination with the operating conditions.

Glycerol is an important quality indicator for foodstuffs. There is an increasing request for one more accurate, reliable, and convenient detection of the glycerol concentrations. Terahertz radiation is highly sensitive to the low-frequency intermolecular interactions between the glycerol and waters. Considering the enhancement property of localized field from the metamaterials, terahertz spectroscopy has been utilized for the determination of glycerol content with metamaterial-based biosensor, where the interaction between the analyte and the terahertz wave can be greatly increased. But the quantitative sensing performance was poor due to the sensitivity limitation of single-mode resonance of metamaterial and the lack of appropriate modeling methods. We propose the optimized structural design with internal coupling and multiple resonances. The induced remarkable changes in the lineshape of different transmitted dip regions imply that our metastructure biosensor is of high sensitivity to the change of surrounding environment on the surface dielectric constant, which has been also verified by coupled Lorentz oscillator theory. Furthermore, the optimal partial least squares regression model with variables of spectral lineshape for the first dip region covering the frequency range of 0.45-0.85 THz was established. It shows more accurate and reliable predictions of glycerol concentrations with residual predictive deviation value of 6.095. Metamaterial-based terahertz spectroscopy combined with statistical modeling with lineshape features can provide one new strategy for quantitative sensing. It has great potential for the improvement of determination of analyte concentrations in the practical applications of food, pharmaceutical or cosmetic area.

The elasticity of a biological tissue can be non-invasively positioned and quantified by ultrasonic elastography, which has a promising application prospect in medical imaging with indistinct boundaries for lesions, especially thermal ablation. This study aims to offer an ultrasonic elastography method that is based on a variable filter length. Compared with the conventional fixed filter length method and according to a strain gradient, the adaptive change of the filter length is allowed, and the motion boundary information between an inclusion and a background tissue is enhanced. With elastic phantoms and fresh porcine liver, the proposed novel method is estimated. The results show that better strain image presentation effects, clearer boundaries, and higher contrast-to-noise ratios (CNRs) have been achieved in regions of interest compared with the conventional method. The CNRs for in vitro experiment are 45.6, 95.0 and 141.2 of the method with M = 80, M = 290, and the proposed method, respectively. It is concluded that ultrasonic elastography based on variable filter length has great potential to be used in clinical applications. Future work will focus on more clinical studies on this method.

We have demonstrated the active manipulation of metamaterial-induced transparency (MIT) in a terahertz hybrid metamaterial with graphene overlayer under photoexcitation. It is found that the introduction of graphene can greatly modify the resonant dips and transparency window through the formed depolarization field around unequal-length double bars to weaken dipole resonances and their destructive interference. Transient control of MIT behaviors is determined by the photogenerated carrier dynamics, which influences the distributions of currents and electric fields in the resonant region to hinder the near-field coupling of two bright modes. Optical modulation depth is sensitive to bar spacing due to an anomalous increased double-bar coupling involving intracell and intercell interaction. Heterointerface formed by the added graphene with substrate could further enhance terahertz response via effective separation of the photoexcited carriers. Theoretical calculation based on the coupled Lorentz oscillator model reveals that the photoinduced terahertz response mainly originates from the coupling and damping in hybrid structures. Our findings could facilitate the development of graphene-based dynamical terahertz modulators and optoelectronic devices.

We have grown VO

A hybrid metamaterial with the integration of molybdenum disulfide (MoS2) overlayer is proposed to manipulate the terahertz (THz) wave. The simulated results indicate that the introduction of MoS2 layer could significantly modify the resonant responses with large resonance red-shift and bandwidth broadening due to the depolarization field effect, especially for the structure on the small permitivity substrate. Additionally, the wide-band modulator in off-resonant region and a switch effect at resonance can be achieved by varying the conductivity of MoS2 layer. Further theoretical calculations based on the Lorentz coupling model are consistent with the simulated results, explicating the response behaviors originate from the coupling between MoS2 overlayer and the metastructure. Our results could provide a possibility for active control THz modulator and switchable device based on the MoS2 overlayer and advance the understanding of the coupling mechanism in hybrid structures.

A photoredox decarboxylative coupling of N-hydroxyphthalimide esters with aldimines is reported for synthesizing α-amino esters. A broad scope of alkyl radicals generated under visible light irradiation adds to glyoxylate aldimines in reliably good to excellent yields. Adding inorganic bases such as potassium carbonate significantly enhanced the yields by suppressing the umpolung side reaction. The computation study suggests that the base facilitates hydrogen atom transfer from the radical cation of Hantzsch ester to the N-centered radical intermediates. Introducing amino acid side chains into natural products and drug molecules by this method is demonstrated.

The construction of county and district medical community is an important measure for high-quality medical resources to "double sink and improve". In this study, we have initially constructed a medical equipment quality control system for members of the regional medical community. The current situation of lack of professional medical equipment management personnel and quality control equipment in primary medical institutions has been alleviated, the quality control level of medical equipment in primary medical institutions has been improved, and a new management model for quality control of primary medical equipment has been explored.