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Solvent-assisted excited state proton transfer and photoacidity of 2-hydroxypyridine. A nonadiabatic dynamics study
摘要： Reactions involving proton transfer, especially those taking place in excited states (ESPT), received considerable attention. These reactions underlie many biological and biochemical processes that are vital to life. DNA mutations excited state funnelling and transport phenomena are just examples. Among many molecules undergoing this type of photoreactions, phenols show a unique property, the so-called photoacidity. In the present communication, solvent (methanol and ammonia) assisted excited state proton transfer and photo acidity of 2-hydroxypyridine (2HP) are investigated at the DFT M06-2X / def2pvv level of theory. Excited states of 2HP and its complexes with methanol and ammonia were examined at two levels. First, sampling a Wigner distribution of 300 points, the photoabsorption spectra were simulated within the nuclear ensemble approximation. Second, simulation of the dynamics of the excited states with the surface hopping method. Several separate spectral windows with three hundred trajectories each, were considered. Lifetime of excited states and photochemical channels observed were discussed.
关键词： nonadiabatic dynamics,photoacidity,Excited state proton transfer (ESPT),photoabsorption spectrum,2-hydroxypyridine
更新于2025-09-09 09:28:46
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Exploring the electromagnetic spectrum with superheroes
摘要： The various radiation types that make up the electromagnetic (EM) spectrum are ubiquitous and highly significant in modern society. Detection of visible light by the eye facilitates sight, radio waves and microwaves are used in communication technologies, x-rays are used in medical imaging, and gamma rays are frequently employed in medical procedures. Although radiation plays a predominant role in daily life, many students have developed and retain misconceptions concerning EM radiation. These misconceptions could be addressed through the use of popular culture content such as superheroes in the classroom. In a number of superhero narratives, EM radiation plays a key role in the emergence or development of superpowers. In this paper, we outline three approaches for using superheroes to support the learning of the EM spectrum, and to potentially address key student misconceptions. In one approach we have designed a student worksheet based on Captain America and vita-rays, a fictional radiation type that plays a key role in his superpowers. The worksheet has been designed to instigate critical reflection on the part of the student, while allowing the student to apply their understanding of other forms of radiation.
关键词： misconceptions,superheroes,electromagnetic spectrum,radiation,education
更新于2025-09-09 09:28:46
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[IEEE 2018 14th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT) - Qingdao, China (2018.10.31-2018.11.3)] 2018 14th IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT) - Emerging Terahertz Technologies for Security, Quality Control, Vision and Medical Applications
摘要： The spectrum of electromagnetic radiation covers a broad range of frequencies, spanning from micro-, millimeter- and radiowaves from one side to visible, ultraviolet and X-ray bands on the other. Nowadays, both these spectral ends are effectively explored in a multitude of devices and applications. In contrast, the intermediate zone, grouping electromagnetic waves of frequencies from 100 GHz to 10 THz, remains largely unexplored, lending itself a name of 'THz gap'. A very useful property of THz radiation is that it easily penetrates through most of non-metallic materials, at the same time providing spectroscopic information for matter classification. It allows to investigate internal structure or content of objects. Also, unlike UV or X-ray, THz waves are non-ionizing and hence harmless to humans and animals, eliminating the need for safety measures.
关键词： Terahertz,non-ionizing,THz gap,electromagnetic spectrum,spectroscopy
更新于2025-09-09 09:28:46
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A New Azimuth Ambiguity Suppression Algorithm for Surface Current Measurement in Coastal Waters and Rivers With Along-track InSAR
摘要： We present a new algorithm for suppressing azimuth ambiguities when measuring surface currents with an along-track interferometric (ATI) synthetic aperture radar in heterogeneous scenes, such as coastal waters or rivers. The key of the proposed algorithm involves a careful analysis of a parameter called the eigenvalue spectrum entropy (EVSE), which is defined as the entropy of the eigenvalue spectrum of the ATI covariance matrix computed in the Doppler domain. The physical meaning of EVSE is that it serves as a descriptor for the degree to which an unambiguous signal component and an ambiguous one are mixed. With the help of EVSE, azimuth ambiguities can be suppressed. Simulation results demonstrate that as compared with the conventional ATI method without azimuth ambiguity suppression, the proposed algorithm allows for a pronounced improvement in the current measuring accuracy. Other advantages of the proposed algorithm lie in the fact that it is not only adaptive, due to its ability to automatically capture the useful Doppler band whose width and position may both vary for different radar and scene parameters, but it also needs a minimal number of user inputs, making it a quite attractive algorithm for routine implementation.
关键词： eigenvalue spectrum entropy (EVSE),current retrieval,surface currents in rivers,ocean surface currents,azimuth ambiguities,Along-track interferometric (ATI) synthetic aperture radar (SAR)
更新于2025-09-09 09:28:46
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Orbital Angular Momentum for Wireless Communications
摘要： As the traditional resources (frequency, time, space, and so on) are efficiently utilized, it becomes more and more challenging to satisfy the ever-lasting capacity-growing and users-boosting demand in wireless networks. Recently, the EM wave was found to possess not only linear momentum, but also angular momentum. The OAM is a kind of wavefront with helical phase. The OAM-based vortex wave has different topological charges, which are orthogonal to each other, bridging a new way for multiple access in wireless communications. In this article, we introduce the fundamental theory of OAM and the OAM based wireless communications. The research challenges regarding OAM signal generation, OAM beam converging, and OAM signal reception are discussed. Further, we propose a new multiuser access with different OAM-modes in wireless networks, where multiple OAM-modes are used as a new orthogonal dimension for interference avoidance. Simulation results reveal the inherent property of OAM waves and show that OAM based radio transmission can significantly increase spectrum efficiency in wireless networks.
关键词： multiple access,spectrum efficiency,OAM,vortex wave,wireless communications
更新于2025-09-09 09:28:46
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Collective effect of single-photon scattering on the three-level atomic array
摘要： From the viewpoint of single-photon scattering, we investigate the collective effect of an alignment of periodically distributed V-type three-level atoms. The electromagnetic field in the free space induces the transitions between the ground state and both of the excited states, and the single-photon scattering process is formulated by the Lippmann-Schwinger equation approach. We study the reflection spectrum and find that the Lamb shift, which is induced by the collective effect of the periodically aligned atoms, is sensitive to the atomic density. Moreover, the interference between two transition channels leads to an asymmetry double-peak reflection spectrum. All of our results can be explained from the singular points of the amplitudes of the atomic excitations. Our work may be helpful to understand the recent experimental results in high-energy-photon scattering on layered nuclei materials.
关键词： Lamb shift,reflection spectrum,single-photon scattering,collective effect,three-level atoms
更新于2025-09-09 09:28:46
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Fluorescence Spectral Study on the Interaction Between Brilliant Blue and Trypsin
摘要： The interaction between brilliant blue and trypsin was studied by using fluorescent technique. The fluorescence quenching data were analyzed according to Stern-Volmer equation and Line weaver-Burk equation. The binding constants, thermodynamic parameters and binding sites were obtained. According to the thermodynamic parameters, the main binding force between brilliant blue and trypsin was ascertained as electrostatic interaction. The binding distance between brilliant blue and trypsin was also given based on the F?rster energy transfer theory.
关键词： Fluorescence spectrum,Thermodynamic parameters,Trypsin,Brilliant blue
更新于2025-09-09 09:28:46
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Impact of Overlapping Fe/TiO <sub/>2</sub> Prepared by Sol-Gel and Dip-Coating Process on CO <sub/>2</sub> Reduction
摘要： Fe-doped TiO2 (Fe/TiO2) film photocatalyst was prepared by sol-gel and dip-coating process to extend its photoresponsivity to the visible spectrum. To promote the CO2 reduction performance with the photocatalyst, some types of base materials used for coating Fe/TiO2, which were netlike glass fiber and Cu disc, were investigated. The characterization of prepared Fe/TiO2 film coated on netlike glass fiber and Cu disc was analyzed by SEM and EPMA. In addition, the CO2 reduction performance of Fe/TiO2 film coated on netlike glass disc, Cu disc, and their overlap was tested under a Xe lamp with or without ultraviolet (UV) light, respectively. The results show that the concentration of produced CO increases by Fe doping irrespective of base material used under the illumination condition with UV light as well as that without UV light. Since the electron transfer between two overlapped photocatalysts is promoted, the peak concentration of CO for the Fe/TiO2 double overlapping is approximately 1.5 times as large as the Fe/TiO2 single overlapping under the illumination condition with UV light, while the promotion ratio is approximately 1.1 times under that without UV light.
关键词： UV light,Fe-doped TiO2,visible spectrum,photocatalyst,dip-coating,sol-gel,CO2 reduction
更新于2025-09-09 09:28:46
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Diagnostics of the Phase Composition of Lead-Zirconate-Titanate Films according to Raman Spectra: Phase Identification
摘要： The problem concerning the diagnostics of the phase composition of lead-zirconate-titanate (PZT) films under conditions of overlapping Raman spectra is solved via applied mathematical statistics. The proposed phase-identification method based on reference spectra is implemented using different Raman-spectrum regions measured on the surface of multiphase PZT films. It is demonstrated that the identification of phases, as well as determination of their concentration, must be performed using the spectral range in which the calculated first principal components of the set of Raman spectra differ to the greatest extent from each other.
关键词： phase identification,Raman spectroscopy,principal-component method,spectrum overlapping
更新于2025-09-04 15:30:14
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Light regulation of vitamin C in tomato fruit is mediated through photosynthesis
摘要： Higher levels of irradiance result in higher accumulation of ascorbate in leaves and fruits. Photosynthesis and respiration are an integral part of the physiological mechanism of light regulation of ascorbate in leaves, but little is known about the light regulation of ascorbate in fruit. The aim of this study was to investigate whether fruit illumination alone is sufficient for ascorbate increase in tomato fruit and whether this light signal is mediated by respiration and photosynthesis. First the changes of ascorbate with the progress of fruit development were investigated and subsequently detached fruit of different tomato genotypes were exposed to different irradiances and spectra. Measurements were performed on ascorbate, respiration, photosynthesis and chlorophyll content of the fruit. When attached to the plant, there was no effect of development on ascorbate from the mature green to the red stage. Detached fruit stored in darkness did not accumulate ascorbate. However, when exposed to 300-600 μmol m-2 s-1 light detached mature green fruit (photosynthetically active) substantially accumulated ascorbate, while mature red fruit (non-photosynthetically active) did not respond to light. Photosynthesis correlated with this increase of ascorbate while no correlation between respiration and ascorbate was found. Spectral effects on ascorbate in detached tomato fruit were limited. These results indicate that the signal for light regulation of ascorbate is perceived locally in the fruit and that fruit illumination alone is sufficient for a considerable increase in ascorbate levels for as long as the fruit contains chlorophyll. It is shown that photosynthetic activity of the fruit is an integral part of the response of ascorbate to light in tomato fruit. The light induced increase in ascorbate levels occurred in a range of genotypes, indicating a universal effect of light to ascorbate in tomato fruit.
关键词： photosynthesis,respiration,vitamin C,irradiance,ascorbic acid,spectrum
更新于2025-09-04 15:30:14