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Photoionization models for extreme Ly <i>α λ</i> 1216 and Hell <i>λ</i> 1640 line ratios in quasar halos, and PopIII vs. AGN diagnostics
摘要： Aims. We explore potential mechanisms to produce extremely high Lyα/HeII ?ux ratios, or to enhance the observed number of Lyα photons per incident ionizing photon, in extended active galactic nucleus (AGN) photoionized nebulae at high-redshift. Methods. We computed models to simulate, in the low density regime, photoionization of interstellar gas by the radiation ?eld of a luminous AGN. We have explored the impact of ionization parameter, gas metallicity, ionizing spectrum, electron energy distribution, and cloud viewing angle on the relative ?uxes of Lyα, HeII and other lines, and on the observed number of Lyα photons per incident ionizing photon. We have compared our model results with recent observations of quasar Lyα halos at z ～ 3.5. Results. Low ionization parameter, a relatively soft or ?ltered ionizing spectrum, low gas metallicity, κ-distributed electron energies, or re?ection of Lyα photons by neutral hydrogen can all result in signi?cantly enhanced Lyα relative to other lines (≥10%), with log Lyα/HeII reaching values of up to 4.6. In the cases of low gas metallicity, re?ection by HI, or a hard or ?ltered ionizing spectrum, the observed number of Lyα photons per incident ionizing photon is itself signi?cantly enhanced above the nominal Case B value of 0.66 due to collisional excitation, reaching values as high as 5.3 in an “extreme case” model which combines several of these e?ects. We ?nd that at low gas metallicity (e.g. Z/Z(cid:12) = 0.1) the production of Lyα photons is predominantly via collisional excitation rather than by recombination. In addition, we ?nd that the collisional excitation of Lyα becomes much more e?cient if the ionizing continuum spectrum has been pre-?ltered through an optically thin screen of gas closer to the AGN (e.g. by a wide-angle, feedback-driven out?ow). We also show that the Lyα and HeII emission line ratios of a sample of previously studied quasars at z ～ 3.5 are consistent with AGN-photoionization of gas with moderate to low metallicity and/or low ionization parameter, without requiring exotic ionization or excitation mechanisms such as strong line-transfer e?ects. In addition, we present a set of UV-optical diagnostic diagrams to distinguish between photoionization by Pop III stars and photoionization by an AGN.
关键词： quasars: emission lines,galaxies: active,galaxies: ISM,galaxies: abundances,galaxies: high-redshift
更新于2025-09-23 15:23:52
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Red-emissive conjugated oligomer/silica hybrid nanoparticles with high affinity and application for latent fingerprint detection
摘要： Latent fingerprint detection plays a great role in forensic science, and considerable efforts have been made on developing efficient and simple strategy to realize clear visualization of latent fingerprints. Among them, fluorescent nanoparticles have attracted increasing interests due to their easy fabrication, good photostability, and low toxicity, but insufficient affinity toward fingerprints has limited their further application. Herein, we report a red-emissive conjugated oligomer/silica hybrid nanoparticle with enhanced affinity toward fingerprints, showing a promising performance on fluorescent detection on latent fingerprints. The conjugated oligomer is covalently doped into the silica nanoparticles, which effectively guarantee its fluorescent quantum yield and photostability. Moreover, the red emission of these nanoparticles also enables the latent fingerprint detection on substrates with fluorescent background, such as plastic and various papers. Most importantly, the introduction of epoxy groups on the silica surface largely enhances its affinity toward fingerprints, compared to that with hydroxy or amino groups, which possibly can be ascribed to its electrostatic attraction and hydrophobic interaction with amino acids and sebaceous substances of fingerprints, respectively.
关键词： Latent fingerprint detection,High affinity,Red emission,Fluorescence,Conjugated oligomer
更新于2025-09-23 15:23:52
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Luminescence enhancement of spherical Sr3La(PO4)3:Eu3+ red nanophosphor with core–shell configuration and added sensitizer for low-voltage field-emission lamp
摘要： Spherical red Sr3La(PO4)3:Bi3+,Eu3+ (SLPO:Bi3+,Eu3+) nanophosphors were synthesized by coprecipitation and thermal annealing for a low-voltage field-emission lamp (FEL). The luminescence intensity of the phosphor was improved using a coreeshell configuration with SiO2 as the core with a diameter of 360 nm and 5e15-nm-thick phosphor as the shell. A 4.4-fold enhancement in the external quantum efficiency (EQE) was obtained. A bright red cathodoluminescence was observed from a 0.25-cm2 FEL at 400 V. The excitation energy efficiently cascade-transferred through the Bi3+ sensitizer to the Eu3+ activator. A coreeshell SLPO:Bi3+,Eu3+ nanophosphor with a maximum EQE of 25.4% and high color purity of 99.7% was obtained when 5-mol% Bi3+ was doped. The energy transfer mechanism and model of the phosphor are proposed.
关键词： Nanophosphor,Sensitizer,Field emission lamp,Coreeshell
更新于2025-09-23 15:23:52
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The near-to-mid infrared spectrum of quasars
摘要： We analyse a sample of 85 luminous (log (νLν(3 μm)/erg s?1) > 45.5) quasars with rest frame ～2–11 μm spectroscopy from AKARI and Spitzer. Their high luminosity allows a direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disc and two blackbodies for the dust emission successfully reproduces the 0.1–10 μm spectral energy distributions (SEDs). Excess emission at 1–2 μm over the best-fitting model suggests that hotter dust is necessary in addition to the ～1200 K blackbody and the disc to reproduce the entire near-infrared spectrum. Variation in the extinction affecting the disc and in the relative strength of the disc and dust components accounts for the diversity of individual SEDs. Quasars with higher dust-to-disc luminosity ratios show slightly redder infrared continua and less prominent silicate emission. We find no luminosity dependence in the shape of the average infrared quasar spectrum. We generate a new quasar template that covers the rest-frame range 0.1–11 μm, and separate templates for the disc and dust components. Comparison with other infrared quasar composites suggests that previous ones are less reliable in the 2–4 μm range. Our template is the first one to provide a detailed view of the infrared emission on both sides of the 4 μm bump.
关键词： infrared: galaxies,galaxies: active,quasars: emission lines,quasars: general
更新于2025-09-23 15:23:52
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Photophysical performance of a rhodamine-MOF composite structure and its sensing potential for picric acid
摘要： For the following paper, a rhodamine-MOF composite structure, RO-EuBTC, was constructed for the optical recognition of PA (picric acid) by the covalent combination of an organic rhodamine dye and rare earth MOF. By means of XRD, IR, TGA, this composite structure was analyzed and confirmed. Its photophysical analysis suggested two sensing aspects towards PA. Be more specific, RO-EuBTC's rhodamine absorption intensity in visible region was proportional to PA, showing colorimetric sensing. RO-EuBTC's rhodamine emission intensity was proportional to PA as well, with its Eu emission intensity inversely proportional to PA, showing self-calibrated sensing signals. Both sensing aspects showed linear response and high selectivity towards PA. Their LOD value was as low as 2.2 μM. Detailed analysis confirmed its sensing mechanism as the combination of two parts, namely the rhodamine emission enhancement sparked by PA's proton and the Eu emission quenching caused by EuBTC's electron transfer to PA. RO-EuBTC was found superior to traditional optical sensing materials based on MOFs owing to its two sensing aspects and the possibility for naked eye detection.
关键词： Self-calibrated signals,Emission increase and decrease,Dynamic sensing,Composite structure
更新于2025-09-23 15:23:52
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Contactless parametric characterization of bandgap engineering in p-type FinFETs using spectral photon emission
摘要： In the last decade it has become increasingly popular to use germanium enriched silicon in modern field effect transistors (FET) due to the higher intrinsic mobility of both holes and electrons in SiGe as compared to Si. Whether used in the source/drain region (S/D) as compressive stressor, which is an efficient mobility booster on Si channel devices, or as channel material, the SiGe increases channel carrier mobility and thus enhancing device performance. Because the germanium content modifies the effective bandgap energy EG, this material characteristic is an important technology performance parameter. The bandgap energy can be determined in an LED-like operation of electronic devices, requiring forward biased p-n junctions. P-n junctions in FETs are source or drain to body diodes, usually grounded or reversely biased. This investigation applies a bias to the body that can trigger parasitic forward operation of the source/drain to body p-n junction in any FET. Spectral photon emission (SPE) is used here as a non-destructive method to characterize engineered bandgaps in operative transistor devices, while the device remains fully functional. Before applying the presented technique to a p-type FinFET device, it is put to the proof by verifying the nominal silicon bandgap on an (unstrained) 120 nm technology FET. Subsequently the characterization capability for bandgap engineering is then successfully demonstrated on a SiGe:C heterojunction bipolar transistor (HBT). In a final step, the bandgap energy EG of a 14/16 nm p-type FinFET was determined to be 0.84 eV, which corresponds to a Si0.7Ge0.3 mixture. The presented characterization technique is a contactless fault isolation method that allows for quantitative local investigation of engineered bandgaps in p-type FinFETs.
关键词： p-n junction,Heterojunction bipolar transistor,Bandgap characterization,p-channel FinFET,SiGe, strained Si,Body diode, parasitic operation,Bandgap engineering,Body bias voltage,HBT,Contactless fault isolation,Spectral photon emission,MOSFET
更新于2025-09-23 15:23:52
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Axial Fourier Rebinning for Time-of-Flight PET
摘要： Fully 3D time-of-flight (TOF) PET scanners offer the potential of substantially improved image quality in clinical PET imaging. The main challenges of 3D TOF PET imaging are the data storage with either list-mode or binned formats, and the reconstruction time using iterative algorithms. Previously, we derived the Fourier rebinning and consistency equations (FORCEs), and showed 3D TOF data can be fully characterized by two consistency equations. In this work, we present an exact Fourier rebinning for 3D TOF data based on the axial consistency equation to dramatically reduce the data storage and the reconstruction time. Starting from pre-corrected 3D TOF data, the axial Fourier rebinning algorithm estimates a 2D TOF sinogram for each transverse slice without information loss. Since the 3D TOF data are axially truncated, we provide a solution to estimate the missing portion in the oblique TOF projection data. The proposed axial Fourier rebinning for TOF data (axFRT) can take advantage of all the 3D TOF data statistics, and the rebinned 2D TOF data can then be reconstructed using any algorithms for 2D or 2.5D TOF reconstructions. The axFRT algorithm allows the axial data sets being rebinned independently, and there are tens of thousands of such data sets which can naturally take advantage of the massively parallel processors to dramatically speedup the rebinning. We show numerical simulations to demonstrate that axFRT produces accurate and unbiased rebinned sinograms even for TOF PET with large axial acceptance angle. The axFRT will be particularly useful for 3D TOF PET with large axial field of view for PET imaging applications including dynamic, whole- or total-body imaging.
关键词： image reconstruction,positron emission tomography (PET),time-of-flight,Axial Fourier rebinning
更新于2025-09-23 15:23:52
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Determination of adulterated gasoline using fluorescence emission-excitation matrices and multivariate calibration
摘要： Methanol gasoline, known as a new energy, has a certain degree of damage to automobile. The aim of this work was to identify and quantify the methanol in methanol gasoline using three-dimensional fluorescence spectroscopy technique combined with second order chemometric methods. Parallel factor analysis (PARAFAC) and self-weighted alternating trilinear decomposition (SWATLD) methods were used to analyse artificial samples. However, the obtained results by PARAFAC were not satisfactory. On the other hand, excellent prediction results were obtained when SWATLD model was applied, with recovery rate between 98.7 and 102.8%, and between 97.4 and 101.9% for two and three factor respectively. In order to verify the accuracy of the method, four real samples were predicted using SWATLD model with RMSEP between 0.1 μg/mL and 0.23 μg/mL.
关键词： SWATLD,Methanol gasoline,PARAFAC,Excitation-emission matrix fluorescence
更新于2025-09-23 15:23:52
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A method for experimental thermo-mechanical aging of materials submitted to concentrated solar irradiation
摘要： Concentrated Solar Technology can produce process heat, power and fuels from solar energy in the temperature range 150–1500 °C, bringing the question of the receiver ability to reliably perform over the expected lifetime. Conventional methods commonly used to assess the mechanical stability and lifetime involve in-door laboratory testing, which suffers from the fundamental inability to reproduce the real operating conditions. A previous work introduced an original experimental setup based on acoustic emission named IMPACT (In situ thermo-Mechanical Probe by ACoustic Tracking), designed for an in situ and passive characterization of receiver materials under harsh thermo-mechanical stresses. This paper proposes an original method, based on a modelling approach, to control the sample damage amplification with IMPACT, and assess its relevance through an experimental campaign on two selected materials (SiC and Inconel 625).
关键词： Central receiver,Thermo-mechanical behaviour,Concentrated Solar Power (CSP),Acoustic Emission
更新于2025-09-23 15:23:52
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Alkyl chains length dependent fluorescence emission and reversible mechanofluorochromism of AIEE-based quinoline derivatives
摘要： Five quinoline derivatives containing different alkyl chains (QLACn, n ? 2, 4, 6, 8, 12) were synthesized to investigate the effect of alkyl chains on their photophysical properties. The ?uorescent properties of the QLACn were affected by the alkyl chains, which indicated obvious blue-shifting trend and ?uorescence emission are alkyl chains length-dependent by grinding-induced spectral shifts (DlMFC). Longer alkyl-length revealed larger DlMFC. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) measurements indicated that the transformation between microcrystalline and amorphous states upon external stimuli should be responsible for the observed reversible MFC behavior.
关键词： Alkyl chains length-dependent behavior,Quinoline derivatives,Aggregation-induced emission enhancement (AIEE) behavior,Mechano?uorochromism behavior
更新于2025-09-23 15:23:52