Catálogo de publicaciones - revistas

<jats:p>We quantify the mean potential energy of a passive colloidal particle harmonically confined in a bacterial solution using optical traps. We find that the average potential energy of the passive particle depends on the trap stiffness, in contrast to the equilibrium case where energy partition is independent of the external constraints. The constraint dependence of the mean potential energy originates from the fact that the persistent collisions between the passive particle and the active bacteria are influenced by the particle relaxation dynamics. Our experimental results are consistent with the Brownian dynamics simulations, and confirm the recent theoretical prediction.</jats:p>

<jats:p>It is of great significance to study the relationship between the excited state intramolecular proton transfer (ESIPT) properties and antioxidant activities of compounds in the field of life sciences. In this work, two novel compounds 5HF–OMe and 5HF–NH<jats:sub>2</jats:sub> are designed through introducing a methoxy- and amino-group into the structure of 5-hydroxyflavone (5HF) respectively. The relationship between the ESIPT reaction and antioxidant activities of the three compounds is studied via the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The calculated potential energy curves suggest that the rate of ESIPT reaction will gradually slow down from 5HF to 5HF–OMe and 5HF–NH<jats:sub>2</jats:sub>. In addition, the antioxidant activities of the three compounds gradually enhance from 5HF to 5HF–OMe and 5HF–NH<jats:sub>2</jats:sub>, which can be seen from the calculated energy gaps and ionization potential values. Interestingly, the above results imply that the rate of ESIPT reaction has a negative relationship with the antioxidant activities of the compounds, <jats:italic>i.e.</jats:italic>, the slower rate of ESIPT reaction will reflect the higher antioxidant activity of the compound, which will provide valuable reference for detecting the antioxidant activity of compound via the photophysical method.</jats:p>

<jats:p>A novel vertical graded source tunnel field-effect transistor (VGS-TFET) is proposed to improve device performance. By introducing a source with linearly graded component, the on-state current increases by more than two decades higher than that of the conventional GaAs TFETs without sacrificing the subthreshold swing (SS) due to the improved band-to-band tunneling efficiency. Compared with the conventional TFETs, much larger drive current range can be achieved by the proposed VGS-TFET with SS below the thermionic limitation of 60 mV/dec. Furthermore, the minimum SS about 20 mV/dec indicates its promising potential for further ultralow power applications.</jats:p>

<jats:p>The self-excited attractors and hidden attractors in a memcapacitive system which has three elements are studied in this paper. The critical parameter of stable and unstable states is calculated by identifying the eigenvalues of Jacobian matrix. Besides, complex dynamical behaviors are investigated in the system, such as coexisting attractors, hidden attractors, coexisting bifurcation modes, intermittent chaos, and multistability. From the theoretical analyses and numerical simulations, it is found that there are four different kinds of transient transition behaviors in the memcapacitive system. Finally, field programmable gate array (FPGA) is used to implement the proposed chaotic system.</jats:p>

<jats:p>This work reports on the integration of organic and inorganic semiconductors as heterojunction active layers for high-performance ambipolar transistors and complementary metal-oxide-semiconductor (CMOS)-like inverters. Pentacene is employed as a p-type organic semiconductor for its stable electrical performance, while the solution-processed scandium (Sc) substituted indium oxide (ScInO) is employed as an n-type inorganic semiconductor. It is observed that by regulating the doping concentration of Sc, the electrical performance of the n-type semiconductor could be well controlled to obtain a balance with the electrical performance of the p-type semiconductor, which is vital for achieving high-performance inverters. When the doping concentration of Sc is 10 at.%, the CMOS-like logic inverters exhibit a voltage gain larger than 80 and a wide noise margin (53% of the theoretical value). The inverters also respond well to the input signal with frequency up to 500 Hz.</jats:p>

<jats:p>It is essential to determine the accumulative ultraviolet (UV) irradiation over a period of time in some cases, such as monitoring UV irradiation to the skin, solar disinfection of water, photoresist exposure, etc. UV colorimetric dosimeters, which use dyes’ color change to monitor the amount of UV exposure, have been widely studied. However, the exposure data of these UV colorimetric dosimeters can hardly be converted to digital signals, limiting their applications. In this paper, a UV dosimeter has been proposed and demonstrated based on the persistent photoconductivity (PPC) in zinc oxide microwires (ZnO MWs). The PPC effect usually results in high photoconductivity gain but low response speed, which has been regarded as a disadvantage for photodetectors. However, in this work, the unique characteristics of the PPC effect have been utilized to monitoring the accumulative exposure. We demonstrate that the photocurrent in the ZnO MWs depends on the accumulative UV exposure due to the PPC effect, thus the photocurrent can be utilized to determine the UV accumulation. The dosimeter is immune to visible light and exhibits a photoconductive gain of 2654, and the relative error of the dosimeter is about 10%. This UV dosimeter with electrical output is reusable and convenient to integrate with other electronic devices and may also open a new application area for the PPC effect.</jats:p>

<jats:p>We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer (HEB) mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer (DATE5) telescope. By evaluating the double sideband (DSB) receiver noise temperature (<jats:italic>T</jats:italic> <jats:sub>rec</jats:sub>) across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points, a broad optimal bias region has been observed, illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point. The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components, whose transmissions have been measured by a time-domain spectroscopy. The corrected noise temperature distribution shows a frequency independence relation. The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated, the bath temperature has limited effect on the lowest receiver noise temperature until 7 K, however the optimal bias region deteriorates obviously with increasing bath temperature.</jats:p>

<jats:p>Parkinson’s disease (PD) is characterized by pathological spontaneous beta oscillations (13 Hz–35 Hz) often observed in basal ganglia (BG) composed of subthalamic nucleus (STN) and globus pallidus (GPe) populations. From the viewpoint of dynamics, the spontaneous oscillations are related to limit cycle oscillations in a nonlinear system; here we employ the bifurcation analysis method to elucidate the generating mechanism of the pathological spontaneous beta oscillations underlined by coupling strengths and intrinsic properties of the STN–GPe circuit model. The results reveal that the increase of inter-coupling strength between STN and GPe populations induces the beta oscillations to be generated spontaneously, and causes the oscillation frequency to decrease. However, the increase of intra-coupling (self-feedback) strength of GPe can prevent the model from generating the oscillations, and dramatically increase the oscillation frequency. We further provide a theoretical explanation for the role played by the inter-coupling strength of GPe population in the generation and regulation of the oscillations. Furthermore, our study reveals that the intra-coupling strength of the GPe population provides a switching mechanism on the generation of the abnormal beta oscillations: for small value of the intra-coupling strength, STN population plays a dominant role in inducing the beta oscillations; while for its large value, the GPe population mainly determines the generation of this oscillation.</jats:p>

<jats:p>Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> solar cells with substrate structure usually suffer from pretty low short circuit current (<jats:italic>J</jats:italic> <jats:sub>SC</jats:sub>) due to the defects and poor carrier transport. The Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub>, as a one-dimensional material, exhibits orientation-dependent carrier transport property. In this work, a thin MoSe<jats:sub>2</jats:sub> layer is directly synthesized on the Mo substrate followed by depositing the Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> thin film. The x-ray diffraction (XRD) patterns confirm that a thin MoSe<jats:sub>2</jats:sub> layer can improve the crystallization of the Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> film and induce (<jats:italic>hk</jats:italic>1) orientations, which can provide more carrier transport channels. Kelvin probe force microscopy (KPFM) results suggest that this modified Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> film has a benign surface with less defects and dangling bonds. The variation of the surface potential of Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> indicates a much more efficient carrier separation. Consequently, the power conversion efficiency (PCE) of the substrate structured Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> thin film solar cell is improved from 1.36 % to 1.86 %, which is the best efficiency of the substrate structured Sb<jats:sub>2</jats:sub>S<jats:sub>3</jats:sub> thin film solar cell, and <jats:italic>J</jats:italic> <jats:sub>SC</jats:sub> significantly increases to 13.6 mA/cm<jats:sup>2</jats:sup>. According to the external quantum efficiency (EQE) and <jats:italic>C</jats:italic>–<jats:italic>V</jats:italic> measurements, the modified crystallization and elevated built-in electric field are the main causes.</jats:p>

<jats:p>The potential mechanisms of the spreading phenomena uncover the organizations and functions of various systems. However, due to the lack of valid data, most of early works are limited to the simulated process on model networks. In this paper, we track and analyze the propagation paths of real spreading events on two social networks: Twitter and Brightkite. The empirical analysis reveals that the spreading probability and the spreading velocity present the explosive growth within a short period, where the spreading probability measures the transferring likelihood between two neighboring nodes, and the spreading velocity is the growth rate of the information in the whole network. Besides, we observe the asynchronism between the spreading probability and the spreading velocity. To explain the interesting and abnormal issue, we introduce the time-varying spreading probability into the susceptible-infected (SI) and linear threshold (LT) models. Both the analytic and experimental results reproduce the spreading phenomenon in real networks, which deepens our understandings of spreading problems.</jats:p>