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Purcell-Dicke enhancement of the Casimir-Polder potential
摘要： The emission by an initially completely inverted ensemble of two-level atoms in the long-wavelength regime is simultaneously enhanced by both collective effects (Dicke effect) and dielectric environments (Purcell effect), thus giving rise to a combined Purcell–Dicke effect. We study this effect by treating the ensemble of N atoms as a single effective N + 1-level "Dicke atom" which couples to the environment-assisted quantum electrodynamic field. We find that an environment can indeed alter the superradiant emission dynamics, as exemplified using a perfectly conducting plate. As the emission acquires an additional anisotropy in the presence of the plate, we find an associated resonant Casimir-Polder potential for the atom that is collectively enhanced and that exhibits a superradiant burst in its dynamics. An additional tuneability of the effect is introduced by applying an external driving laser field.
关键词： superradiant emission,quantum electrodynamics,Purcell-Dicke effect,Casimir-Polder potential
更新于2025-09-09 09:28:46
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Triphenylethylene- and Tetraphenylethylene-Functionalized 1,3-Bis(pyrrol-2-yl)squaraine Dyes: Synthesis, Aggregation-Caused Quenching to Aggregation-Induced Emission, and Thiol Detection
摘要： Three novel pairs of 1,3-bis(pyrrol-2-yl)squaraine dyes, N-alkylated SQ1a?1b, and N-phenylated SQ2a?2b in which triphenylethylene moieties functionalized at 5-position of pyrrole, as well as SQ3a?3b with tetraphenylethylene (TPE) moieties attached at N-position of pyrrole, were synthesized. All six dyes were found not to exhibit aggregation-induced emission (AIE) properties. Spectrophotometric studies showed that N-TPE-functionalized SQ3a?3b exhibited much larger molar extinction coefficients (ε: 1.36?2.14 × 105 M?1 cm?1) than 5,5′-triphenylethylene-functionalized SQ1a?2b (ε: 2.17?8.22 × 104 M?1 cm?1). Surprisingly, SQ2b showed a remarkable red-shifted maximum absorption (λmax: 723 vs 631?652 nm) compared to that of other squaraine dyes. All six squaraine dyes selectively responded to the addition of thiol-containing biomolecules, such as cysteine and gluthatione, with the disappearance of λmax in the near-infrared region in their respective absorption spectra. Interestingly, the thiolated species of SQ3a?3b were AIE active, with the characteristic AIE emission of TPE at λmax = 484?490 nm upon addition of water. Further thiol sensing on solid supports was examined, indicating the potential applications of TPE-functionalized squaraine dyes as bioprobes for the detection of important thiol-containing biomolecules, with a clear change from aggregation-caused quenching to AIE.
关键词： bioprobes,aggregation-induced emission,near-infrared,thiol detection,squaraine dyes
更新于2025-09-09 09:28:46
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Nonparametric H Density Estimation Based on Regularized Nonlinear Inversion of the Lyman Alpha Emission in Planetary Atmospheres
摘要： Inversion of space-borne remote sensing measurements of the resonantly scattered solar Lyman alpha (121.6-nm) emission in planetary atmospheres is the most promising means of quantifying the H density in a vast volume of space near terrestrial planets. Owing to the highly nonlinear nature of the inverse problem and the lack of sufficient data constraints over the large volume of space where H atoms are present, previous inversion methods relied on physics-based parametric formulations of the H density distributions to guarantee solution uniqueness. Those physical formulations, such as the Chamberlain model, were developed with simple assumptions of the atmospheric conditions. The use of such formulations as constraints significantly limits the range of possible solutions, which might lead to large errors in the case when those assumptions are invalid. In this study, we demonstrate for the first time the feasibility of estimating the H density through regularized nonlinear inversion of the Ly-?? emission in an optically thick atmosphere, without using parametric formulations. Specifically, Occam’s inversion algorithm is used to demonstrate that the H density can be estimated in a large volume of space near the planet, with accuracy in different atmospheric regions depending on the observation scheme. Two distinctly different schemes are examined, including a low-Earth orbit and a geostationary orbit. Modeling results show that the low-Earth orbit is better for H density estimation in the thermosphere, while the high-altitude orbit is better for estimation in the exosphere. Our results could provide useful information for designing the observation schemes of future missions.
关键词： H density estimation,regularized nonlinear inversion,Occam’s inversion algorithm,planetary atmospheres,Lyman alpha emission
更新于2025-09-09 09:28:46
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Budget impact from the incorporation of positron emission tomography – computed tomography for staging lung cancers
摘要： OBJECTIVE: To estimate the budget impact from the incorporation of positron emission tomography (PET) in mediastinal and distant staging of non-small cell lung cancer. METHODS: The estimates were calculated by the epidemiological method for years 2014 to 2018. Nation-wide data were used about the incidence; data on distribution of the disease′s prevalence and on the technologies’ accuracy were from the literature; data regarding involved costs were taken from a micro-costing study and from Brazilian Unified Health System (SUS) database. Two strategies for using PET were analyzed: the offer to all newly-diagnosed patients, and the restricted offer to the ones who had negative results in previous computed tomography (CT) exams. Univariate and extreme scenarios sensitivity analyses were conducted to evaluate the influence from sources of uncertainties in the parameters used. RESULTS: The incorporation of PET-CT in SUS would imply the need for additional resources of 158.1 BRL (98.2 USD) million for the restricted offer and 202.7 BRL (125.9 USD) million for the inclusive offer in five years, with a difference of 44.6 BRL (27.7 USD) million between the two offer strategies within that period. In absolute terms, the total budget impact from its incorporation in SUS, in five years, would be 555 BRL (345 USD) and 600 BRL (372.8 USD) million, respectively. The costs from the PET-CT procedure were the most influential parameter in the results. In the most optimistic scenario, the additional budget impact would be reduced to 86.9 BRL (54 USD) and 103.8 BRL (64.5 USD) million, considering PET-CT for negative CT and PET-CT for all, respectively. CONCLUSIONS: The incorporation of PET in the clinical staging of non-small cell lung cancer seems to be financially feasible considering the high budget of the Brazilian Ministry of Health. The potential reduction in the number of unnecessary surgeries may cause the available resources to be more efficiently allocated.
关键词： Health Care Costs,Carcinoma, Non-Small-Cell Lung, therapy,Budgets,Positron-Emission Tomography, economics,Unified Health System
更新于2025-09-09 09:28:46
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Spectropolarimetry of Seyfert 1 galaxies with equatorial scattering: black hole masses and broad-line region characteristics
摘要： Here we present the spectropolarimetric observations of a sample of 30 Type 1 active galactic nuclei (AGNs) and an analysis of the observed polarization in these AGNs. The observations have been performed with the 6 m telescope of SAO RAS using the modified SCORPIO-2 spectropolarimeter. We measured the Stokes parameters for the continuum and the broad H α line and obtained the values of polarization degree and the angle of polarization. We found that equatorial scattering is dominant polarization mechanism in the sample that allows us to use the observed polarization in the broad lines for determination of the central black hole (BH) masses and characteristics (the inclination and emissivity) of the broad-line region (BLR). We demonstrated that the recently proposed method of Afanasiev & Popovi′c (2015) for BH mass measurement gives accurate BH masses that are in a good correlation with the stellar velocity dispersion, and consequently, the masses determined by the polarization method can be used with calibration purposes. Additionally we found that the BLR in the sample of 30 AGNs has an averaged inclination of 35?±9? (mostly between 20? and 40?) and emissivity α ～ ?0.57 that is more flat than one expected for the classical accretion disc α ～ ?0.75.
关键词： quasars,quasars: supermassive black holes,line: profiles,emission lines,polarization,galaxies: nuclei,galaxies: active
更新于2025-09-09 09:28:46
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Spectral signatures of fluorescence and light absorption to identify crude oils found in the marine environment
摘要： To protect the natural marine ecosystem, it is necessary to continuously enhance knowledge of environmental contamination, including oil pollution. Therefore, to properly track the qualitative and quantitative changes in the natural components of seawater, a description of the essential spectral features describing petroleum products is necessary. This study characterises two optically-different types of crude oils (Petrobaltic and Romashkino) – substances belonging to multi-fluorophoric systems. To obtain the spectral features of crude oils, the excitation-emission spectroscopy technique was applied. The fluorescence and light absorption properties for various concentrations of oils at a stabilised temperature are described. Both excitation-emission spectra (EEMs) and absorption spectra of crude oils are discussed. Based on the EEM spectra, both excitation end emission peaks for the wavelength-independent fluorescence maximum (Exmax/Emmax) – characteristic points for each type of oil – were identified and compared with the literature data concerning typical marine chemical structures.
关键词： seawater,Excitation-emission spectra,fluorescence spectroscopy,oil pollution,absorption spectra
更新于2025-09-09 09:28:46
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Imaging Spectrum and Pitfalls of <sup>11</sup> C-Methionine Positron Emission Tomography in a Series of Patients with Intracranial Lesions
摘要： 11C-methionine (Met) positron emission tomography (PET) is one of the most commonly used PET tracers for evaluating brain tumors. However, few reports have described tips and pitfalls of 11C-Met PET for general practitioners. Physiological 11C-Met uptake, anatomical variations, vascular disorders, non-tumorous lesions such as inflammation or dysplasia, benign brain tumors and patient condition during 11C-Met PET examination can potentially affect the image interpretation and cause false positives and negatives. These pitfalls in the interpretation of 11C-Met PET images are important for not only nuclear medicine physicians but also general radiologists. Familiarity with the spectrum and pitfalls of 11C-Met images could help prevent unfavorable clinical results caused by misdiagnoses.
关键词： Inflammation,Methionine,Positron-emission tomography,Brain tumors,Vascular diseases
更新于2025-09-09 09:28:46
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Mechanical Insights into Aggregation-Induced Delayed Fluorescence Materials with Anti-Kasha Behavior
摘要： Organic materials with aggregation-induced delayed fluorescence (AIDF) have exhibited impressive merits for improving electroluminescence efficiency and decreasing efficiency roll-off of nondoped organic light-emitting diodes (OLEDs). However, the lack of comprehensive insights into the underlying mechanism may impede further development and application of AIDF materials. Herein, AIDF materials consisting of benzoyl serving as an electron acceptor, and phenoxazine and fluorene derivatives as electron donors are reported. They display greatly enhanced fluorescence with increased delayed component upon aggregate formation. Experimental and theoretical investigations reveal that this AIDF phenomenon can be rationally ascribed to the suppression of internal conversion and the promotion of intersystem crossing in solid. Moreover, the theoretical calculations disclose that the efficient solid-state delayed fluorescence originates from the higher energy electronic excited state (e.g., S2) rather than the lowest energy-excited state (S1), demonstrating an anti-Kasha behavior. The excellent AIDF property allows high exciton utilization and thus superb performance of OLEDs using these new materials as light-emitting layers.
关键词： aggregation-induced delayed fluorescence,anti-Kasha emission,intersystem crossing,internal conversion,organic light-emitting diodes
更新于2025-09-09 09:28:46
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Molecular Imaging of Neuroinflammation in HIV
摘要： The development of combined antiretroviral therapy (cART) has increased the lifespan of persons living with HIV (PLWH), with most PLWH having a normal life expectancy. While significant progress has occurred, PLWH continue to have multiple health complications, including HIVassociated neurocognitive disorders (HAND). While the exact cause of HAND is not known, persistent neuroinflammation is hypothesized to be an important potential contributor. Molecular imaging using positron emission tomography (PET) can non-invasively evaluate neuroinflammation. PET radiotracers specific for increased expression of the translocator protein18kDa (TSPO) on activated microglia can detect the presence of neuroinflammation in PLWH. However, results from these studies have been inconsistent and inconclusive. Future studies are needed to address key limitations that continue to persist with these techniques before accurate conclusions can be drawn regarding the role of persistent neuroinflammation in PLWH.
关键词： Neuroinflammation,Human immunodeficiency virus (HIV),Positron emission tomography (PET),Translocator protein 18 kDa (TSPO),HIV-associated neurocognitive impairment (HAND)
更新于2025-09-09 09:28:46
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Rapid Detection of Aromatic Pollutants in Water Using Swellable Micelles of Fluorescent Polymers
摘要： We constructed a kind of novel swellable fluorescent micelles for rapid and sensitive detection of toxic aromatic pollutants (APs) in water based on capture-report strategy. An amphiphilic triblock copolymer capped with an aggregation induced emission (AIE) chromophore self assembled into micelles with core-shell structures in aqueous solution. Hydrophobic segments of block polymers organized into cores with the AIE chromophore near the core/shell interface, which were stabilized by a corona of water-soluble polymer segments. Water-soluble polymer segments captured APs in water. The captured pollutants were subsequently transported to hydrophobic cores of micelles. The cores swelled after absorbing APs, leading to fluorescence quenching of the AIE chromophores. The fluorescent micelles allowed rapid detection of APs in the order of seconds at a concentration of 1 ug/L. Compared with commercial GC-MS, the fluorescent micelles require a much smaller amount sample and are much quicker with comparable sensitivity. With the merits of high sensitivity, rapid response, simple operation procedures, and low cost, the fluorescent micelles provide an ideal candidate for the facile detection of toxic aromatic pollutants in water.
关键词： Polymer,Fluorescence,Micelle,Aromatic pollutant,Aggregation-induced emission
更新于2025-09-09 09:28:46