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Field-emission nanodiodes with air-gap channels based on single ß-Ga2O3 nanowires have been investigated in this work. With a gap of â¼50 nm and an asymmetric device structure, the proposed nanodiode achieves good diode characteristics through field emission in air at room temperature. Measurement results show that the nanodiode exhibits an ultrahigh emission current density, a high enhancement factor of >2300, and a low turn-on voltage of 0.46 V. More impressively, the emission current almost keeps constant over a wide range (8 orders of magnitude) of air pressures below 1 atm. Meanwhile, the fluctuation in field-emission current is below 8.7% during long-time monitoring, which is better than the best reported field-emission device based on ß-Ga2O3 nanostructures. All of these results indicate that ß-Ga2O3 air-gapped nanodiodes are promising candidates for vacuum electronics that can also operate in air.
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Mobile visible light communication (VLC) is key for integrating lighting and communication applications in the 6G era, yet there exists a notable gap in experimental research on mobile VLC. In this study, we introduce a mobile VLC system and investigate the impact of mobility speed on communication performance. Leveraging a laser-based light transmitter with a wide coverage, we enable a light fidelity (LiFi) system with a mobile receiving end. The system is capable of supporting distances from 1 m to 4 m without a lens and could maintain a transmission rate of 500 Mbps. The transmission is stable at distances of 1 m and 2 m, but an increase in distance and speed introduces interference to the system, leading to a rise in the Bit Error Rate (BER). The mobile VLC experimental system provides a viable solution to the issue of mobile access in the integration of lighting and communication applications, establishing a solid practical foundation for future research.
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The expression changes of baculovirus inhibitor of apoptosis repeat-containing protein5 in brain glioma after administration of Scutellarin was detected. To explore the effort of scutellarin on anti-glioma by downregulating BIRC5.The effect of scutellarin on tumour growth and animal survival was detected by administering scutellarin to nude mice subcutaneous tumour formation and SD rats in situ tumour formation models. A significantly different gene BIRC5 was found by using the combination of TCGA databases and network pharmacology. And then qPCR was performed to detect the expression of BIRC5 in glioma tissues, cells and normal brain tissues and glial cells. CCK-8 was used to detect the IC50 of scutellarin on glioma cells. The wound healing assay, flow cytometry and MTT test were used to detect the effect of scutellarin on the apoptosis and proliferation of glioma cells. The expression of BIRC5 in glioma tissues was significantly higher than that in normal brain tissues. Scutellarin can significantly reduce tumour growth and improve animal's survival. After scutellarin was administered, the expression of BIRC5 in U251 cells was significantly reduced. And after same time, apoptosis increased and cell proliferation was inhibited. This original research showed that scutellarin can promote the apoptosis of glioma cells and inhibit the proliferation by downregulating the expression of BIRC5.
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Neoplasias Encefálicas , Glioma , Camundongos , Ratos , Animais , Camundongos Nus , Ratos Sprague-Dawley , Apoptose , Proliferação de Células , Glioma/tratamento farmacológico , Glioma/genética , Glioma/metabolismo , Linhagem Celular Tumoral , Neoplasias Encefálicas/patologia , Regulação Neoplásica da Expressão GênicaRESUMO
As the key component to transmit power and torque, the fault diagnosis of rotating machinery is crucial to guarantee the reliable operation of mechanical equipment. Regrettably, sample class imbalance is a common phenomenon in industrial applications, which causes large cross-domain distribution discrepancies for domain adaptation (DA) and results in performance degradation for most of the existing mechanical fault diagnosis approaches. To address this issue, a novel DA approach that simultaneously reduces the cross-domain distribution difference and the geometric difference is proposed, which is defined as MRMI. This work contains three parts to improve the sample class imbalance issue: (1) A novel distance metric method (MVD) is proposed and applied to improve the performance of marginal distribution adaptation. (2) Manifold regularization is combined with instance reweighting to simultaneously explore the intrinsic manifold structure and remove irrelevant source-domain samples adaptively. (3) The â2-norm regularization is applied as the data preprocessing tool to improve the model generalization performance. The gear and rolling bearing datasets with class imbalanced samples are applied to validate the reliability of MRMI. According to the fault diagnosis results, MRMI can significantly outperform competitive approaches under the condition of sample class imbalance.
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Extending the applications of Photoremovable Protecting Groups (PPGs) to "cage" phenols has generally met with unusually complex PPG byproducts. In this study, we demonstrate that the p-hydroxyphenacyl (pHP) cage for both simple and complex phenolics, including tyrosine, dispenses free phenols. With the simpler unsubstituted phenols, the reaction is governed by their Brønsted Leaving Group ability. On the other hand, the byproducts of the cage vary with these phenols. For the more acidic phenols the cage byproduct follows the Favorskii rearrangement to form p-hydroxyphenylacetic acid whereas for the weaker phenols other reactions such as reduction and hydrolysis begin to emerge. When the photolysis is conducted in octa acid (OA) containers, non-Favorskii, unrearranged fragments of the cage and other byproducts arise.
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Parity-time-symmetric (PT-symmetric) optical waveguide couplers offer a great potential for future applications in integrated optics, such as ultracompact reconfigurable all-optical signal processing. Here, we predict a nonlinearly triggered transition from a full to a broken PT-symmetric regime in finite-size systems described by smooth permittivity profiles and, in particular, in a conventional discrete waveguide directional coupler configuration with a rectangular profile. For these systems, we show that this phase transition occurs in PT-symmetric couplers, regardless of the details of their geometry, therefore suggesting a practical route for experimental realization of such systems.
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The decomposed plastic products in the natural environment evolve into tiny plastic particles with characteristics such as small size, lightweight, and difficulty in removal, resulting in a significant pollution issue in aquatic environments. Significant progress has been made in microplastic separation technology benefiting from microfluidic chips in recent years. Based on the mechanisms of microfluidic control technology, this study investigates the enrichment and separation mechanisms of polystyrene particles in an unbuffered solution. The Faraday reaction caused by the bipolar electrodes changes the electric field gradient and improves the separation efficiency. We also propose an evaluation scheme to measure the separation efficiency. Finite element simulations are conducted to parametrically analyze the influence of applied voltages, channel geometry, and size of electrodes on plastic particle separation. The numerical cases indicate that the electrode-installed microfluidic channels separate microplastic particles effectively and precisely. The electrodes play an important role in local electric field distribution and trigger violent chemical reactions. By optimizing the microchannel structure, applied voltages, and separation channel angle, an optimal solution for separating microplastic particles can be found. This study could supply some references to control microplastic pollution in the future.
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We report a Cu(I)-Ph-BPE-catalyzed asymmetric vinylogous Mannich reaction of ß,γ-alkynyl-α-ketimino esters with ß,γ-unsaturated N-acylpyrazoles. In this process, the Cu(I)-Ph-BPE catalyst activates the ß,γ-alkynyl-α-ketimino ester through N,O-coordination, enabling the subsequent nucleophilic addition of a dienolate generated from the ß,γ-unsaturated N-acylpyrazole via α-position deprotonation with a catalytic amount of tertiary amine. The reactions gave useful products with very high enantioselectivities. A broad range of substrates with various substituents are tolerated in this reaction. The versatility of this method was demonstrated by a gram-scale reaction, and subsequent elaboration of the Mannich adducts was also provided.
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The electronic interaction between a metal and a support modulates the electronic structures of supported metals and plays an important role in manipulating their catalytic performance. However, this interaction is mainly realized in heterogeneous catalysts composed of reducible oxides. Herein, we demonstrate the electronic interaction between γ-Al2O3 and η-Al2O3 with varying acid-base properties and supported Pd nanoparticles (NPs) of 2 nm in size. The strength and number of acid-base sites on the supports and catalysts were systemically characterized by FT-IR spectroscopy and TPD. The supported Pd NPs exhibit electron-rich surface properties by receiving electrons from the electron-donating basic sites on γ-Al2O3, which are beneficial for catalyzing the hydrogenation of nitrobenzene. In contrast, Pd NPs loaded on η-Al2O3 are electron-deficient because of the rich electron-withdrawing acid sites of η-Al2O3. As a result, Pd/η-Al2O3 exhibits higher catalytic activity in phenylacetylene hydrogenation than Pd/γ-Al2O3. Our results suggest a promising route for designing high-performance catalysts by adjusting the acid-base properties of Al2O3 supports to maneuver the electronic structures of metals.
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Magnetic fluid is a new type of smart material, which holds implications for highly enhancing the oil displacement efficiency. In the present study, we perform a comprehensive investigation to probe the influence of a magnetic fluid on the displacement efficiency in porous media under the action of magnetic force. First, the displacement efficiency is measured by a self-developed setup, where factors such as the magnet thicknesses, the volume of the fluid injected, the fluid injection speed, and the porosity of the sample are surveyed as controllable variables. Moreover, the experimental results are well verified by the scaling laws according to the principle of dimensional balance. Next, a numerical simulation is performed to explore the detailed displacement process. First, the magnetic force generated by the ring magnet is calculated. Then, the function curves of the displacement efficiency with respect to the controlling variables are validated by the numerical simulation. In addition, the numerical simulation also demonstrates the volume phase distribution, the pressure field, and the velocity field of the mixed fluid during the displacement process. The simulation results are in excellent agreement with the experimental data. These findings are beneficial for us to better understand the oil displacement with the aid of external fields, which also provide inspiration for the areas of microfluidics, diffusion of pollutants, microsensors, etc.
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Electrospray ionization of methanolic solutions of p-hydroxyphenacyl derivatives HO-C(6)H(4)-C(O)-CH(2)-X (X = leaving group) provides abundant signals for the deprotonated species which are assigned to the corresponding phenolate anions (-)O-C(6)H(4)-C(O)-CH(2)-X. Upon collisional activation in the gas phase, these anions inter alia undergo loss of a neutral "C(8)H(6)O(2)" species concomitant with formation of the corresponding anions X(-). The energies required for the loss of the neutral roughly correlate with the gas phase acidities of the conjugate acids (HX). Extensive theoretical studies performed for X = CF(3)COO in order to reveal the energetically most favorable pathway for the formation of neutral "C(8)H(6)O(2)" suggest three different routes of similar energy demands, involving a spirocyclopropanone, epoxide formation, and a diradical, respectively.
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Acetofenonas/química , Ânions/química , Ciclopropanos/química , Compostos de Epóxi/química , Gases Nobres/química , Compostos de Espiro/química , Modelos Teóricos , Estrutura Molecular , Soluções/química , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
Frequency stabilization can overcome the dependence of resonance frequency on amplitude in nonlinear microelectromechanical systems, which is potentially useful in nonlinear mass sensor. In this paper, the physical conditions for frequency stabilization are presented theoretically, and the influence of system parameters on frequency stabilization is analyzed. Firstly, a nonlinear mechanically coupled resonant structure is designed with a nonlinear force composed of a pair of bias voltages and an alternating current (AC) harmonic load. We study coupled-mode vibration and derive the expression of resonance frequency in the nonlinear regime by utilizing perturbation and bifurcation analysis. It is found that improving the quality factor of the system is crucial to realize the frequency stabilization. Typically, stochastic dynamic equation is introduced to prove that the coupled resonant structure can overcome the influence of voltage fluctuation on resonance frequency and improve the robustness of the sensor. In addition, a novel parameter identification method is proposed by using frequency stabilization and bifurcation jumping, which effectively avoids resonance frequency shifts caused by driving voltage. Finally, numerical studies are introduced to verify the mass detection method. The results in this paper can be used to guide the design of a nonlinear sensor.
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The existing available research outcomes on vibration attenuation control for time-delay feedback indicate that, for the delay dynamic vibration absorber with fixed time-delay control parameters, under harmonic excitation, a good vibration attenuation control effect occurs on the vibration of the main system. However, the effect is not obvious for complex excitation. Aiming at the above problems, in a short time interval, a harmonic excitation with the same displacement size as the complex excitation was established. Then, by calculating its equivalent amplitude and equivalent frequency, a harmonic equivalent method for complex excitation was proposed in this paper. The time-delay parameters were adjusted according to the equivalent frequency of harmonic equivalent excitation in real time; therefore, a good vibration attenuation control effect was obtained through the delay dynamic vibration absorber in the discrete time interval. In this paper, research on a time-varying delay dynamic vibration absorber was conducted by taking the two-degree-of-freedom vibration system with a delay dynamic vibration absorber as an example. The simulation results show that the proposed control method can reduce the vibration of the main system by about 30% compared with the passive vibration absorber. This can obviously improve the performance of the time-delay dynamic vibration absorber. It provides a new technical idea for the design of vehicle active frame system.
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PURPOSE: Accumulating evidence indicates that oxidative stress may play an important role in the pathogenesis of type 2 diabetes and its complications. Lycopene, a very potent antioxidant of carotenoids, has received considerable scientific interest in recent years for its potential role in the prevention of oxidative stress-related chronic diseases. This study was undertaken to investigate whether the serum levels of lycopene are altered between type 2 diabetic patients with and without diabetic retinopathy. METHODS: A total of 71 patients with type 2 diabetes were analyzed and compared with 23 nondiabetic healthy controls. Serum lycopene concentrations were assayed using high-performance liquid chromatography. RESULTS: Lycopene level was found to be significantly lower in diabetic patients than in controls (p = 0.021). In the diabetic group, subjects with proliferative diabetic retinopathy had significantly lower lycopene levels than subjects without diabetic retinopathy or with nonproliferative diabetic retinopathy. In the analysis of correlations, hemoglobin A1c were negatively correlated with lycopene (r = -0.345, p = 0.007) after multivariate adjustment. A stepwise linear multiple regression model revealed that age and hemoglobin A1c were significant determinants of lycopene. CONCLUSIONS: Our findings show that measuring serum lycopene is a novel convenient method for evaluating oxidative damage. Diabetic patients, especially those with advanced diabetic retinopathy, had significantly lower serum lycopene levels; this suggests that lycopene may be helpful for the diagnosis, severity, and therapeutic evaluation of diabetic retinopathy.
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Carotenoides/sangue , Retinopatia Diabética/sangue , Estresse Oxidativo/fisiologia , Biomarcadores/sangue , Cromatografia Líquida de Alta Pressão , Diabetes Mellitus Tipo 2/sangue , Progressão da Doença , Feminino , Humanos , Licopeno , Masculino , Pessoa de Meia-Idade , PrognósticoRESUMO
Liquid coating films on solid surfaces exist widely in a plethora of industrial processes. In this study, we focus on the falling of a liquid film on the side surface of a vertical cylinder, where the surface is viewed as slippery, such as a liquid-infused surface. The evolution profiles and flow instability of the advancing contact line are comprehensively analyzed. The governing equation of the thin film flow is derived according to the lubrication model, and the traveling-wave solutions are numerically obtained. The results show that the wave speed increases with the increase of a larger slippery length. A linear stability analysis (LSA) is carried out to verify the traveling solutions and time responses. Although previous studies tell us that the wall slippage always promotes the surface flow instability of the thin film flow, the linear stability analysis, numerical simulations, and nonlinear traveling-wave solutions in the current study present a different conclusion. The analysis show that for a thin film flow with a dynamic contact line the wall slippage in different directions plays much more complex roles. The streamwise slippery effect always impedes the instability of the flow and suppresses the wave height of traveling wave, while the transverse slippery effect has a dual effect on the surface instability. The transverse slippery effect significantly improves the instability while the wave number of the perturbation is small, and simultaneously it reduces the cutoff wave number. The transverse slippery effect will change its role if the wave number of the perturbation exceeds a critical value, which can stabilize the contact line.
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Microelectromechanical switch has become an essential component in a wide variety of applications, ranging from biomechanics and aerospace engineering to consumer electronics. Electrostatically actuated microbeams and microplates are chief parts of many MEMS instruments. In this study, the nonlinear characteristics of coupled longitudinal-transversal vibration are analyzed, while an electrostatically actuated microbeam is designed considering that the frequency ratio is two to one between the first longitudinal vibration and transversal vibration. The nonlinear governing equations are truncated into a set of coupled ordinary differential equations by the Galerkin method. Then the equations are solved using the multiple-scales method and the nonlinear dynamics of the internal resonance is investigated. The influence of bias voltage, longitudinal excitation and frequency detuning parameters are mainly analyzed. Results show that using the pseudo-arclength continuation method, the nonlinear amplitude-response curves can be plotted continuously. The saturation and jump phenomena are greatly affected by the bias voltage and the detuning frequency. Beyond the critical excitation amplitude, the response energy will transfer from the longitudinal motion to the transversal motion, even the excitation is employed on the longitudinal direction. The large-amplitude jump of the low-order vibration mode can be used to detect the variation of the conditions or parameters, which shows great potential in improving precision of MEMS switches.
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This paper details study of the anti-symmetric response to the symmetrical electrostatic excitation of a Micro-electro-mechanical-systems (MEMS) resonant mass sensor. Under higher order mode excitation, two nonlinear coupled flexural modes to describe MEMS mass sensors are obtained by using Hamilton's principle and Galerkin method. Static analysis is introduced to investigate the effect of added mass on the natural frequency of the resonant sensor. Then, the perturbation method is applied to determine the response and stability of the system for small amplitude vibration. Through bifurcation analysis, the physical conditions of the anti-symmetric mode vibration are obtained. The corresponding stability analysis is carried out. Results show that the added mass can change the bifurcation behaviors of the anti-symmetric mode and affect the voltage and frequency of the bifurcation jump point. Typically, we propose a mass parameter identification method based on the dynamic jump motion of the anti-symmetric mode. Numerical studies are introduced to verify the validity of mass detection method. Finally, the influence of physical parameters on the sensitivity of mass sensor is analyzed. It is found that the DC voltage and mass adsorption position are critical to the sensitivity of the sensor. The results of this paper can be potentially useful in nonlinear mass sensors.
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[reaction: see text] Photolysis of alpha-keto amides bearing 4-YC(6)H(4)O leaving groups at the position alpha to the keto group efficiently produces high yields of phenols when Y is an electron-withdrawing group or H. The photoelimination likely involves cleavage of zwitterionic intermediates produced via excited-state hydrogen transfer. When Y is an electron-donating group, competing excited-state ArO-C(alpha) bond scission to radicals occurs, followed by recombination to give 1,3-photorearrangment products.
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Carboxylate groups incorporated at the position alpha to the keto carbonyl of alpha-keto amides 1 were photochemically cleaved in aqueous media to give carboxylic acids in 70-90% yields with quantum yields of 0.3. The cleavage coproducts were diastereomeric hemiacetals 2. Prompt release of acetate and gamma-aminobutyrate (GABA) in buffer was observed by difference FT-IR spectroscopy upon 355 nm laser flash photolysis. The time-constant for release of GABA was <30 ms. [reaction--see text]
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Amidas/química , Ácidos Carboxílicos/química , Fotólise , Acetatos/química , Cetonas/química , Estrutura Molecular , Espectroscopia de Infravermelho com Transformada de Fourier , Ácido gama-Aminobutírico/químicaRESUMO
This study investigated the clinical value of diffusion tensor imaging (DTI) in predicting the motor outcome in patients with basal ganglia hemorrhage. This prospective study included 23 patients assessed with DTI to measure the fractional anisotropy (FA) value in affected cortical spinal tract (CST) at three time points: day 0, day 30 and day 90 after onset. The motor function score (MFS) was applied to evaluate motor function and patients were divided into good and poor outcome groups according to the MFS on day 90. The mean FA value on day 0 was significantly lower in the poor outcome group than in the good outcome group (p<0.01). FA value gradually decreased in the poor outcome group until day 90 after onset, while it continuously increased in the good outcome group. The MFS obtained at day 90 after onset was significantly correlated with the initial FA value in the affected cerebral peduncle (r=-0.926, p<0.01). Receiver operating characteristic curve analysis showed that the FA value on day 0 could predict motor function outcome with a sensitivity of 88.89% and specificity of 92.86% at the initial FA value of 0.45. The FA value of affected CST in acute cerebral hemorrhage may valuably predict the motor function outcome and its dynamic change may represent the Wallerian degeneration in motor tracts after hemorrhagic stroke.