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Sensing of airborne molecular contaminants based on microfiber coupler with mesoporous silica coating
摘要： Airborne molecular contaminants (AMCs) are critical issues for the performance of optics in high power lasers (HPLs). In this work we demonstrate an AMCs sensor based on an optical microfiber coupler (OMC) with mesoporous silica coating experimentally. AMCs adhered on the mesoporous silica coating modifies the surrounding refractive index (RI). Using Beam Propagation Method (BPM), the proposed structure was analyzed to demonstrate the feasibility of AMCs sensing. By coating a mesoporous silica layer on the surface of sensing area, the proposed structure was able to operate as an AMCs sensor. By monitoring the spectral shift in the wavelength domain, the sensor was shown to be capable of detecting concentration of AMCs. The experimental results show that the sensitivity of the sensor is concentration-dependent. The maximum sensitivity of 0.541nm/(mg/m3) is achieved. The detected signal is found to be proportional to AMCs present.
关键词： Airborne molecular contaminants (AMCs),Beam propagation method,Optical microfiber coupler (OMC),Evanescent field
更新于2025-09-23 15:22:29
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Microscopy and Spectroscopy Study of Nanostructural Phase Transformation from β-MoO3 to Mo under UHV – MBE Conditions
摘要： We report a simple reduction of molybdenum oxide (β-MoO3) grown on reconstructed Si(100) by thermal annealing in ultra-high vacuum (UHV) using molecular beam epitaxy (MBE). By increasing the substrate temperature during deposition or the annealing temperature after growth, the morphologies of as-deposited structures were found to vary from nanoribbons (NRs) of β-MoO3 to nanoparticles (NPs) of Mo. The change in morphologies have been associated with a structural transition from β-MoO3 to MoO2 at 400 °C and MoO2 to Mo at 750 °C. The in-situ X-ray photoelectron spectroscopy (XPS) measurements revealed a shift of the Mo 3d peaks towards lower binding energies, representing the reduction in Mo oxidation states until a pure Mo 3d peak at 750°C was observed. The ex-situ KPFM measurements showed a decrease in the local work function (Φ) (from ≈ 5.27 ± 0.05 eV to ≈ 4.83 ± 0.05 eV) with increasing substrate temperature. A gradual reduction of the band gap from ≈ 3.32 eV for β-MoO3 NRs to zero band gap for Mo NPs is also observed during the annealing up to 750 °C.
关键词： in-situ XPS,KPFM,molecular beam epitaxy (MBE),Mo nanoparticles,β-MoO3 nanoribbons,phase transition
更新于2025-09-23 15:22:29
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Research of the substituent effect on non-linear optical properties of bis(difluoroboron)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (BOPHY) derivatives: Molecular simulation analyses
摘要： Modelling studies of bis(difluoroboron)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (BOPHY) derivatives were completed at M06-2X/6-31+G(d) level in vacuo. Structural properties (geometric structure, bond lengths and angles), spectral electronic properties and non-linear optical properties (NLO) of related boron complexes were investigated. Geometric parameters of mentioned boron complexes and electronic structures of them were reported. IR spectrum of boron complexes are calculated in vacuo and potential energy distribution (PED) analyses of frequencies were done. UV-VIS spectrum were calculated in gas phase (ε=1), toluene (ε=2.3741), chloroform (ε=4.7113), methanol (ε=32.613), water (ε=78.3553) and n-methylformamide-mixture (ε=181.56) at M06-2X/6-31+G(d), wB97X-D/6-31+G(d) and CAM-B3LYP/6-31+G(d) levels. Wavelength of observed bands in UV-VIS spectrum were used in the interpretation of optical activity. Molecular orbital energy diagram (MOED), contour diagrams of certain molecular orbitals, density of state (DOS) spectrum and molecular electrostatic potential (MEP) maps are calculated to determination of electronic properties and NLO activity. Finally, some quantum chemical descriptors were calculated and analyzed in determination of NLO properties. It is found that compound 5 and 6 are found as the good materials for NLO applications.
关键词： Hydrazine,Molecular Simulations,BOPHY,Bipyrrole,Optical Properties
更新于2025-09-23 15:22:29
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Photo-induced lattice contraction in layered materials
摘要： Structural and electronic changes induced by optical excitation is a promising technique for functionalization of 2D crystals. Characterizing the effect of excited electronic states on the in-plane covalent bonding network as well as the relatively weaker out-of-plane dispersion interactions is necessary to tune photo-response in these highly anisotropic crystal structures. In-plane atom dynamics was measured using pump-probe experiments and characterized using ab initio simulations, but the effect of electronic excitation on weak out-of-plane van der Waals bonds is less well-studied. We use non-adiabatic quantum molecular dynamics to investigate atomic motion in photoexcited MoS2 bilayers. We observe a strong athermal reduction in the lattice parameter along the out-of-plane direction within 100 fs after electronic excitation, resulting from redistribution of electrons to excited states that have lesser anti-bonding character between layers. This non-trivial behavior of weakly bonded interactions during photoexcitation could have potential applications for modulating properties in materials systems containing non-covalent interactions like layered materials and polymers.
关键词： quantum molecular dynamics,layered materials,MoS2,photo-dynamics,van der Waals
更新于2025-09-23 15:22:29
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[IEEE 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Athens, Greece (2018.7.4-2018.7.6)] 2018 41st International Conference on Telecommunications and Signal Processing (TSP) - Modeling Electromagnetic Wireless Nanonetworks in Terahertz Band within NS-3 Platform
摘要： The wireless nanosensor network paradigm has seen a dramatic increase over the last decade. The envisioned concept uses the integrated machines (devices) at the nano-scale level. Those devices interact on a cooperative basis by means of principles known in wireless communication networks. Today, the design of the protocol stack for wireless nanosensor networks represents the crucial issue to be addressed. Currently available tools only support molecular-based approaches without the ability to account for the relevant impact that electromagnetic communications may have in this field. To cover this white spot, in this paper, the theoretical comparison of available simulation tools is given. Further, we focus on the Nano-Sim tool and create the scenario for wireless sensor networks (WNSN) based on electromagnetic communication in terahertz band.
关键词： Nanonetworks,Network Simulator 3,Simulation tools,Performance evaluation,Molecular communication
更新于2025-09-23 15:22:29
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Femtosecond Optical Annealing Induced Polymer Melting and Formation of Solid Droplets
摘要： Interaction between femtosecond laser pulses with polymeric thin films induced transient optical annealing of the polymer molecules. Melting of the polymer films took place during the transient annealing process, so that a solid-liquid-solid phase transition process was observed. Ultrafast cooling of the melting polymer produced solidified droplets. Microscopic and spectroscopic characterization revealed that the polymer molecules were rearranged with preferable H-aggregation to reach the lowest formation energy during the melting process. Intermolecular coupling was enhanced due to the modified molecular arrangement. This observation of melting of polymeric semiconductors due to the interaction with femtosecond light pulses is potentially important for better understanding laser-matter interactions and for exploring organic optoelectronic devices through special material processing.
关键词： transient optical annealing,melting polymer droplets,solid-liquid-solid phase transition,femtosecond laser-matter interaction,molecular rearrangement
更新于2025-09-23 15:22:29
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<sup>18</sup> F-Fluoride Signal Amplification Identifies Microcalcifications Associated With Atherosclerotic Plaque Instability in Positron Emission Tomography/Computed Tomography Images
摘要： BACKGROUND: Microcalcifications in atherosclerotic plaques are destabilizing, predict adverse cardiovascular events, and are associated with increased morbidity and mortality. 18F-fluoride positron emission tomography (PET)/computed tomography (CT) imaging has demonstrated promise as a useful clinical diagnostic tool in identifying high-risk plaques; however, there is confusion as to the underlying mechanism of signal amplification seen in PET-positive, CT-negative image regions. This study tested the hypothesis that 18F-fluoride PET/CT can identify early microcalcifications. METHODS: 18F-fluoride signal amplification derived from microcalcifications was validated against near-infrared fluorescence molecular imaging and histology using an in vitro 3-dimensional hydrogel collagen platform, ex vivo human specimens, and a mouse model of atherosclerosis. RESULTS: Microcalcification size correlated inversely with collagen concentration. The 18F-fluoride ligand bound to microcalcifications formed by calcifying vascular smooth muscle cell derived extracellular vesicles in the in vitro 3-dimensional collagen system and exhibited an increasing signal with an increase in collagen concentration (0.25 mg/mL collagen ?33.8×102±12.4×102 counts per minute; 0.5 mg/mL collagen ?67.7×102±37.4×102 counts per minute; P=0.0014), suggesting amplification of the PET signal by smaller microcalcifications. We further incubated human atherosclerotic endarterectomy specimens with clinically relevant concentrations of 18F-fluoride. The 18F-fluoride ligand labeled microcalcifications in PET-positive, CT-negative regions of explanted human specimens as evidenced by 18F-fluoride PET/CT imaging, near-infrared fluorescence, and histological analysis. Additionally, the 18F-fluoride ligand identified micro and macrocalcifications in atherosclerotic aortas obtained from low-density lipoprotein receptor-deficient mice. CONCLUSIONS: Our results suggest that 18F-fluoride PET signal in PET-positive, CT-negative regions of human atherosclerotic plaques is the result of developing microcalcifications, and high surface area in regions of small microcalcifications may amplify PET signal.
关键词： molecular imaging,fluoride,atherosclerosis,positron emission tomography,microcalcification
更新于2025-09-23 15:22:29
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Prognostic Investigations of Expression Level of Two Genes FasL and Ki-67 as Independent Prognostic Markers of Human Retinoblastoma
摘要： In this study, expression of FasL and Ki-67 messenger RNA (FasL and Ki-67 mRNA) in human retinoblastoma (HRB) was examined by the immunohistochemistry method and quantitative real-time PCR. Positive expression of Ki-67 in tumor cells was detected in 16 of 30 patients (53.33%), and only 9 (30%) of the tissues from patients with retinoblastoma showed positive staining for FasL. Our results revealed that FasL expression was significantly higher in tumor tissue with invasion compared with the noninvasion form (p = 0.033). Ki-67 expression was markedly increased in tumor tissues with invasion compared with the noninvasion group (p = 0.04), but no significant correlation was found between FasL expression and differentiation (p > 0.05). In addition, Ki-67 expression was strongly linked to differentiation (p < 0.002). Expression of these FasL was correlated with shorter overall survival of patients, but its expression was not significantly associated with overall survival (p = 0.15). The impact of Ki-67 expression on survival in patients was also evaluated. Ki-67 expression level was not found to be significantly associated with shorter survival (Kaplan–Meier; p = 0.09). Univariate analysis revealed that massive choroidal invasion was correlated with poor prognosis. Taken together, the data suggest that massive choroidal invasion is also an important indicator of poor prognosis for HRB.
关键词： Expression,Analysis,Retinoblastoma (RB),Ki-67 and FasL,Molecular
更新于2025-09-23 15:22:29
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Light-powered, artificial molecular pumps: a minimalistic approach
摘要： The realization of artificial molecular motors capable of converting energy into mechanical work is a fascinating challenge of nanotechnology and requires reactive systems that can operate away from chemical equilibrium. This article describes the design and construction of a simple, supramolecular ensemble in which light irradiation causes the directional transit of a macrocycle along a nonsymmetric molecular axle, thus forming the basis for the development of artificial molecular pumps.
关键词： molecular machine,azobenzene,rotaxane,supramolecular chemistry,photochemistry
更新于2025-09-23 15:22:29
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Recent Advancement of Semiconductor Materials and Devices
摘要： 本論文では, 主に GaAs および GaAs 系混晶半導体の MBE 成長とそのデバイス応用について取り上げたが, その他にも窒化物半導体, 酸化物半導体, II-VI 族半導体といった多くの半導体の成長や, 量子細線, 量子ドットのような量子井戸以上に複雑な構造の製作にも MBE 法は活用されている. 基礎研究から実用化まで, 半導体デバイスの開発において MBE 法が成し遂げてきた功績は極めて大きい. 今後も素子構造の製作, 新規半導体材料の成長, 結晶欠陥の制御など様々な要求のある結晶成長時に MBE 法は活用され続けるであろう.
关键词： Compound semiconductors,Optical and electronic devices,Molecular beam epitaxy
更新于2025-09-23 15:22:29