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O12 scintillator
摘要： The characteristics of a Gd3Al2Ga3O12 crystal scintillator doped with cerium and co-doped with magnesium and titanium have been studied, mainly in view of using it for the Phase II upgrade of the LHCb electromagnetic calorimeter. Samples of the scintillator were irradiated with γ (60Co) to 2 kGy and with 24 GeV protons to 900 kGy. The proton fluence value was ～3·1015 cm?2. It was found that γ-irradiation did not produce any change in the optical transmission of the crystals in the spectral range of the scintillation light, whereas a degradation after the proton irradiation was measurable. For the 1 cm thick sample, a loss of transmission of 3.6% was measured at the wavelength of maximum scintillation (520 nm), and the measured induced absorption coefficient at this wavelength was ～3.6 m?1. The formation of radioisotopes in the crystal at proton irradiation has been analyzed. The formation of isotopes was also simulated with the help of the FLUKA package. The simulation was found to be in a good agreement with experimental results. The results have been used to estimate the expected intensity of parasitic radio-luminescence at high-luminosity operation in a GAGG/W sampling electromagnetic calorimeter.
关键词： Electromagnetic calorimetry,radiation damage,gadolinium-aluminum-gallium garnet,optical transmission,scintillation crystal
更新于2025-09-09 09:28:46
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Resonant states in double and triple quantum wells
摘要： The full set of resonant states in double and triple quantum well/barrier structures is investigated. This includes bound, anti-bound and normal resonant states which are all eigensolutions of Schr?dinger’s equation with generalized outgoing wave boundary conditions. The transformation of resonant states and their transitions between different subgroups as well as the role of each subgroup in observables, such as the quantum transmission, is analyzed. The quantum well potentials are modeled by Dirac delta functions; therefore, as part of this study, the well known problem of bound states in delta-like potentials is also revisited.
关键词： resonant states,quantum transmission,delta-like potentials
更新于2025-09-09 09:28:46
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Kinetics of liquid-mediated crystallization of amorphous Ge from multi-frame dynamic transmission electron microscopy
摘要： The kinetics of laser-induced, liquid-mediated crystallization of amorphous Ge thin films were studied using multi-frame dynamic transmission electron microscopy (DTEM), a nanosecond-scale photo-emission transmission electron microscopy technique. In these experiments, high temperature gradients are established in thin amorphous Ge films with a 12-ns laser pulse with a Gaussian spatial profile. The hottest region at the center of the laser spot crystallizes in (cid:2)100 ns and becomes nano-crystalline. Over the next several hundred nanoseconds crystallization continues radially outward from the nano-crystalline region forming elongated grains, some many microns long. The growth rate during the formation of these radial grains is measured with time-resolved imaging experiments. Crystal growth rates exceed 10 m/s, which are consistent with crystallization mediated by a very thin, undercooled transient liquid layer, rather than a purely solid-state transformation mechanism. The kinetics of this growth mode have been studied in detail under steady-state conditions, but here we provide a detailed study of liquid-mediated growth in high temperature gradients. Unexpectedly, the propagation rate of the crystallization front was observed to remain constant during this growth mode even when passing through large local temperature gradients, in stark contrast to other similar studies that suggested the growth rate changed dramatically. The high throughput of multi-frame DTEM provides gives a more complete picture of the role of temperature and temperature gradient on laser crystallization than previous DTEM experiments.
关键词： liquid-mediated crystallization,dynamic transmission electron microscopy,amorphous Ge,kinetics,laser-induced crystallization
更新于2025-09-09 09:28:46
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Transmission electron microscopy revealing the mechanism of action of photodynamic therapy on Trichomonas vaginalis
摘要： Trichomonas vaginalis is an amitochondrial parasite that causes human trichomoniasis. Despite metronidazole effectiveness, resistant cases are becoming more frequent. This scenario reveals the need to develop new therapeutic options. Photodynamic Therapy (PDT) is an experimental treatment that involves the activation of photosensitive substances and the generation of cytotoxic oxygen species and free radicals to promote the selective destruction of target tissues. In previous work, we identified an excellent in vitro PDT activity using methylene blue and light emitting diode against metronidazole sensitive and resistant strains of T. vaginalis. Here, we evaluated the efficacy of PDT in vivo and its high trichomonicidal activity was assessed through transmission electron microscopy. Female Balb/c mice were infected intravaginally with T. vaginalis trophozoites. On the third day of infection, methylene blue was introduced into the vaginal canal, which then received 68.1 J / cm2 of radiation for 35.6 sec. Twenty-four hours after treatment the vaginal canal of the animals was scraped and the samples processed by the immunocytochemistry technique. Besides that, in vitro photodynamic treatment was performed and T. vaginalis trophozoites were processed by transmission electron microscopy. PDT significantly reduced infection in animals treated, compared to control groups, being as efficient as metronidazole. Morphological changes observed have suggested that PDT activity on T. vaginalis was due to necrosis. These results, added to the high trichomonicidal activity of PDT confirm its feasibility for trichomoniasis treatment.
关键词： Methylene Blue,Transmission Electron Microscopy,Trichomonas vaginalis,Photodynamic Therapy,Treatment
更新于2025-09-09 09:28:46
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Distributed Strain Sensing Using Electrical Time Domain Reflectometry With Nanocomposites
摘要： The objective of this study is to validate distributed strain sensing using electrical time domain reflectometry (ETDR) with multi-walled carbon nanotube (MWCNT)-based thin film sensing elements. The proposed ETDR sensor composed of two types of transmission lines: parallel-wire-type transmission line and parallel-plate-type transmission line with MWCNT-based sensing elements. The hypothesis was that the greater strain-induced impedance changes of the nanocomposite would enhance ETDR sensing performance. In this paper, four different types of ETDR sensing elements were subjected to one-cycle uniaxial tensile strains to validate strain sensing. Three sensing elements were then integrated in an ETDR setup, and strain patterns were applied for validating their distributed strain sensing behavior.
关键词： transmission line,Carbon nanotubes,thin film,strain sensing,electrical time domain reflectometry
更新于2025-09-09 09:28:46
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Polarization-Tracking-Free PDM Supporting Hybrid Digital-Analog Transport for Fixed-Mobile Systems
摘要： For ?xed services such as hybrid ?ber-coaxial (HFC) and passive optical network (PON) with deployed ?ber networks, it is desirable to exploit the potentials to support wireless services in ?fth-generation (5G) mobile data communications on top of the existing ?xed networks. We propose a polarization-division multiplexing (PDM) scheme to achieve co-delivery of independent signals for ?xed-mobile convergence. This is achieved by removing unwanted optical carrier in each polarization, thus the proposed system can resolve the polarization-tracking issue in conventional PDM. It has been demonstrated in this letter that the polarization-tracking-free PDM system can support co-transmission of respective 70-Gbps digital and analog signals over 20-km single mode ?ber. Experimental results have shown low crosstalk between two polarizations. The proposed PDM system is compatible with wavelength-division-multiplexing (WDM) network and is capable of enhancing the spectral ef?ciency of WDM channels. The inherent single-sideband feature of the proposed PDM also enhances long-range services.
关键词： Polarization division multiplexing,?xed-mobile convergence,hybrid digital-analog transmission,polarization-tracking free
更新于2025-09-09 09:28:46
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Young’s Modulus of Fullerene C <sub/>60</sub> –C <sub/>70</sub> Alloy Crystalline Nanowhiskers
摘要： Crystalline nanowhiskers (NWs) composed of fullerene C60 and C70 molecules, i.e., alloy NWs, were synthesized by a liquid–liquid interfacial precipitation method. The nominal composition of C70 ranged from 0 to 40 mass%. The bending tests of the alloy NWs were performed inside a high-resolution transmission electron microscope, and the deformation behavior was observed in situ. The bending force acting on the NWs were measured simultaneously by an optical deflection method, and the Young’s modulus was estimated from the resulting force–flexure curves. The average Young’s modulus was found to increase to approximately 30 GPa as the C70 composition was increased to the solubility limit. In contrast, the Young’s modulus decreased with increasing NW diameter caused by the addition of C70.
关键词： Fullerene,Bending,Young’s Modulus,Transmission Electron Microscopy,Nanowhisker
更新于2025-09-09 09:28:46
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Nonlinearity-free Coherent Transmission in Hollow-Core Antiresonant Fiber
摘要： We demonstrate the first multi-terabit/s WDM data transmission through hollow-core antiresonant fiber (HC-ARF). 16 channels of 32-GBd dual-polarization (DP) Nyquist-shaped 256QAM signal channels were transmitted through a 270-m long fiber without observing any power penalty. In a single-channel high power transmission experiment, no nonlinearity penalty was observed for up to 1 W of received power, despite the very low chromatic dispersion of the fiber (<2 ps/nm/km). Our simulations show that such a low level of nonlinearity should enable transmission at 6.4 Tb/s over 1200 km of HC-ARF, even when the fiber attenuation is significantly greater than that of SMF-28. As signals propagate through hollow-core fibers at close to the speed of light in vacuum such a link would be of interest in latency-sensitive data transmission applications.
关键词： Hollow-core Antiresonant Fiber,Fiber nonlinearity,Optical fiber communication,Coherent transmission,Modulation
更新于2025-09-09 09:28:46
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-II
摘要： The basic and the charge density wave (CDW) structures of the monoclinic NbS3-II polymorph were studied by synchrotron x-ray diffraction, ab initio calculations, simulation of electron diffraction patterns, and by atomic-resolution transmission electron and low-temperature scanning tunneling microscopies. It is con?rmed that the basic structure belongs to the space group P 21/m and is described with a unit cell, formed of four pairs of symmetry-related trigonal prismatic (TP) columns [a0 = 0.96509(8) nm, b0 = 0.33459(2) nm, c0 = 1.9850(1) nm, and β0 = 110.695(4)?]. The incommensurate components of the two CDWs, (cid:3)q1 = (0, 0.298, 0) and (cid:3)q2 = (0, 0.352, 0), are related as q1b + 2q2b ≈ 1. Both CDWs form their own modulation patterns with unit cells (am = 2a0, bm = b0/qjb, cm = c0, βm = β0) and are ordered along adjacent isosceles TP columns either pairwise or with both columns modulated by either the (cid:3)q1 or (cid:3)q2 CDW only. The CDWs are ordered according to one of the two possible modulation pattern space groups, Cm or C2/m. If considered as long-period commensurate, the entire modulated structure with both CDWs included is described within experimental error with an enlarged unit cell (a = 2a0, b = 37b0, c = c0, and β = β0) and with all atoms displaced from their average positions in accord with the speci?ed modulation pattern.
关键词： synchrotron x-ray diffraction,ab initio calculations,charge density wave,scanning tunneling microscopy,transmission electron microscopy,NbS3-II
更新于2025-09-09 09:28:46
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Silicide phase formation by Mg deposition on amorphous Si. Ab initio calculations, growth process and thermal stability
摘要： Formation of magnesium silicides on amorphous silicon by deposition of Mg at room temperature is studied by electron energy loss spectroscopy, differential reflectance spectroscopy and high resolution transmission electron microscopy. Optimal crystal structures of Mg silicides under high pressure are found by ab initio DFT calculations. These structures are related to the particular minima of enthalpy. Dielectric functions are calculated for these structures. The transitions from the cubic phase c-Mg2Si to orthorhombic o-Mg2Si at 5.6 GPa and then from o-Mg2Si to hexagonal h-Mg2Si at 22.3 GPa are predicted using the USPEX code. The experimental spectra and the data obtained from the calculated dielectric functions are mutually consistent. Optical reflectance is suitable for monitoring the growth and transformations of the phases during experiments. During Mg deposition onto amorphous Si, the o-Mg2Si phase forms first, then the c-Mg2Si phase grows upon it. The observed sequence of phase formation is related with the compression stress arising in the depth of the Mg-Si mixture.
关键词： optical reflection spectroscopy,electron energy loss spectroscopy,solid state reactions,thin films,high resolution transmission electron spectroscopy,ab initio calculations
更新于2025-09-09 09:28:46