[en] Highlights: • Total 28 Λ-S states of the NTe molecule have been calculated for the first time. • The polarity of the ground state for NTe is determined to be N^δ−Te^δ+. • The SOC effects make the lowest 10 Λ-S states split into 30 Ω states. • The Ω-state transitions borrow TDMs from the spin-allowed Λ-S transitions via SOC. - Abstract: The entire 28 Λ-S electronic states correlated to four dissociation limits of the NTe molecule have been reliably characterized for the first time. The potential energy curves (PECs) and wavefunctions of these Λ-S states are calculated using the multi-reference configuration interaction plus Davidson correction (MRCI+Q) approach, with all-electron correlation-consistent basis sets at quadruple-zeta level. The spectroscopic constants of the bound Λ-S states are determined from the PECs, and the excellent agreement with previous work is derived. By analyzing the dipole moment, the polarity of the ground state for NTe is determined to be N^δ−Te^δ+, which is contrary to the case of NO. The spin-orbit coupling (SOC) effect is included when the state interaction method is applied. The SOC effect is found to be substantial for the NTe molecule, which makes the lowest 10 Λ-S states split into 30 Ω states. The X²Π states split into two Ω states including X²Π_1/2(X₁1/2) and X²Π_3/2(X₂3/2), and the corresponding SOC splitting is computed to be 1975 cm⁻¹(0.245 eV). Analysis of Λ-S compositions for the Ω-state wavefunction indicates the strong interaction among the Λ-S states. Additionally, the transition properties of the Ω-state transitions 1/2(2)-X₁1/2, 1/2(4)-X₁1/2, 3/2(10)-X₂3/2, and 5/2(1)-X₂3/2 were predicted. These transitions are all mainly from the spin-forbidden Λ-S transitions, but their transition dipole moments arise from those of the spin-allowed Λ-S transitions via the SOC effect. Accordingly, these transitions have quite long radiative lifetimes that are at the microsecond (ms) level.

[en] Tb³⁺ doped SiO₂-ZnO-BaO glasses are prepared by melting quenching method and their unique photoluminescent properties for the UV excitation are studied by using emission/excitation spectra and decay curves. Glasses in the composition (mol%) of 60SiO₂-xZnO-(40-x)BaO-0.2Tb³⁺(x=30, 20, 10) show the strongest emission peaking at 436 nm which is different from majority of other reported work. Lower content of the free OH groups mainly contribute to this phenomenon due to the decreased probability of the multi-phonon aided non-radiative relaxation process from ⁵D₃ to ⁵D₄ energy levels of Tb³⁺ ions. The Tb³⁺ concentration also affects the ⁵D₃/⁵D₄ emissions as a result of the cross-relaxation effect on two nearby Tb³⁺ ions (⁵D₃-⁵D₄⇒⁷F₆-⁷F₀). Moreover, by adjusting Tb³⁺ concentration and/or ZnO/BaO concentration ratio of the host glass we obtained the adjustable emission with the required CIE chromaticity from blue to green, suggesting that the present Tb³⁺-doped SiO₂-ZnO-BaO glasses are potential as blue/green dual-color luminescent materials for different applications.

[en] Experiments were performed on a high-speed online random neutron analyzing system (HORNA system) with a ²⁵²Cf neutron source (up to 1 GHz sampling rate and 3 input data channel), to obtain time-and frequency dependent signatures which are sensitive to changes in the composition, fissile mass and configuration of the fissile assembly. The data were acquired by three high-speed synchronized acquisition cards at different detector angles, source-detector distances and block sizes. According to the relationship between ²⁵²Cf source and the ratio of power spectral density, R_psd, all the signatures were calculated and analyzed using correlation and periodogram methods. Based on the results, the simulated autocorrelation functions were utilized for identifying different fissile mass with Elman neural network. The experimental results show that the R_psd almost remains at constant amplitude in frequency range of 0-100 MHz, and is only related to the angle and source-detector distance. The trained Elman neural network is able to distinguish the characteristics of autocorrelation function and identify different fissile mass. The average identification rate reached 90% with high robustness. (authors)

[en] Objective: To investigate the diagnostic value of DWI on nasopharyngeal neoplasm recurrence and fibrotic lesions after radiotherapy. Methods: A retrospective analysis pathologically confirmed nasopharyngeal neoplasm was performed in 39 patients with recurrent patients(recurrence group) confirmed by biopsy or MRI follow-up and 51 patients with confirmed localized fibrosis(fibrosis group) after radiotherapy. All patients underwent DWI, non-enhanced and enhanced MR scan. DWI findings and ADC values of the lesions in two groups of patients were observed and measured, then compared by using independent samples t test. Diagnostic performance of routine MRI and DWI in the diagnosis of nasopharyngeal neoplasm recurrence after radiotherapy was calculated by using ROC analysis and the differences of both of them were analyzed by using Z test. Results: DWI of 39 recurrent patients showed hyper-intensity signal and ADC map showed hypo-intensity signal appearance. Overall signal of DWI in 51 recurrent patients is lower than that in recurrent group, in which ADC maps of 36 cases showed iso-intensity or moderately hypo-intensity signal appearance and the remaining 15 cases showed moderate hyper-intensity signal appearance. The ADC values of recurrent group and fibrotic group were (0.753 ± 0.127) × 10^-3 mm²/s, and (1.233 ± 0.310) × 10^-3 mm²/s, respectively. The difference was statistically (t = -9.118, P < 0.05). On the ROC curve, the sensitivity of ADC for the diagnosis of tumor recurrence was 87.18% (34/39), specificity 94.12%(48/51) and area under the ROC curve 0.968 with the ADC cutoff value of 0.887 × 10^-3 mm²/s. The sensitivity of routine MRI was 71.79%(28/39), the specificity 74.51%(38/51) and the area under the ROC curve was 0.732 for the diagnosis of tumor recurrence. The difference of area under the curve between them was statistically significant (Z = 4.583, P < 0.01). Conclusion: DWI can help tumor detection and diagnosis of recurrent nasopharyngeal neoplasm and has a higher diagnostic performance compared with routine MRI. (authors)

[en] Correct and effective identification of nuclear material is a key part for nuclear weapon's verification. Based on the nuclear information system constructed with ²⁵²Cf spontaneous neutron source, the simulated autocorrelation functions are utilized for identification of different fissile mass with Elman neural network. The experimental results show the trained Elman neural network is able to distinguish the characteristics of autocorrelation function, identify different fissile mass, and the average identification rate reaches 85% and keep average synthesis error smaller than 0.04 with high robustness. (authors)

[en] Highlights: • The Eu-based MOFs characterized with ability of arsenate ion luminescence sensing and entrapping. • Arsenate ion sensing with detection limit down to 17.8 nM, much lower than the upper limit that WHO set for public health. • High recognition specificity in luminescence sensing and rate in adsorption of arsenate ions. A new type of Eu-based metal organic framework (Eu-MOF) characterized with ability of arsenate ion luminescence sensing and entrapping was constructed via solvothermal method based on the optimization of the organic ligand. The Eu-MOF aqueous dispersion sample displayed arsenate-triggered augment in luminescence emission intensity with appreciable contrast and detection sensitivity with limit of detection down to 17.8 nM toward arsenate ion, which is less than one-fourth of the upper limit concentration of arsenic in drinking water that the World Health Organization (WHO) set for public health, 72 nM. Additionally, the excellent recognition specificity Eu-MOF toward arsenate species over various potential interfering anions and cations was also confirmed. The rapid adsorption ability of Eu-MOF nanostructures toward arsenate in aqueous milieu that plausibly originated from its nature of chemical adsorption and the adsorption feature conforming to the Langmuir model was also verified. The advantages that Eu-MOF nanostructure displays in terms of high sensitivity and recognition specificity in luminescence sensing of arsenate ion and the desired arsenate entrapping ability in aqueous milieu is expected to impart it potential for sensing and entrapping trace amount of arsenate in water in practical applications.

[en] Highlights: • The reported phosphor of Zn₂SiO₄ showed obvious green long persistent phosphorescence. . • The properties and attributions of defects in the phosphors were studied using the compound determination technologies. • The luminescence mechanism was constructed by band theory and defect theory. A green long persistent phosphor (LPP) Zn_2-δSiO_4-δ with ${\text{V}}_{\text{Zn}}^{"}$ defects as emission centers was synthesized using a conventional solid-state reaction. The samples were analyzed by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), thermoluminescence (TL) techniques and electron paramagnetic resonance (EPR). Rietveld refinement of the XRD patterns confirmed the willemite structure of Zn₂SiO₄ with minor impurity of SiO₂. There is one main emission peak of the green phosphor at 521​nm attributed to ${\text{V}}_{\text{Zn}}^{"}\text{defects}$ as emission centers. TL curves and the spectra of EPR showed that the defect concentration of phosphors was enhanced by sintering in the reducing atmosphere and Zn deficiency to improve the properties of the phosphor. The long-lasting luminescence of Zn_2-δSiO_4-δ was observed for more than 4​h by naked eyes in darkness. The mechanism of photoluminescence of zinc deficiency persistent phosphor was explored.

[en] Highlights: • The reported phosphor of Sr₃Al₂O₆:Pr³⁺ showed obvious orange-reddish long persistent phosphorescence. . • The properties and attributions of defects in the phosphors were studied using the compound determination technologies. • The luminescence mechanism was constructed by band theory and defect theory. The orange-reddish Sr₃Al₂O₆:Pr³⁺ samples were prepared using solid state reaction in air and the photoluminescence properties of the phosphors were investigated. The as-prepared phosphors were studied systematically by X-ray diffraction, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectra, afterglow decay curves, thermoluminescence (TL) glow spectra, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR). The luminescence of Pr³⁺-activated Sr₃Al₂O₆ exhibited a strong emission peak at 611​nm under 246​nm excitation arising from the intrinsic f-f transition of Pr³⁺ as an emitting centre. The ions of Pr³⁺ acted as not only the activators but also the providers of traps. The doping concentration of Pr³⁺ has a significant effect on the photoluminescence and long afterglow luminescence. The TL process and possible luminescence working mechanism of the Sr₃Al₂O₆:Pr³⁺ were discussed in detail. The suitable and effective trap depths as well as the high concentration of defects for Sr₃Al₂O₆ phosphors were obtained though the introduction of Pr³⁺ ions, greatly extending the lifespan of the electron-hole pair in the lattices for the improvement of the luminescent properties of Sr₃Al₂O₆ long afterglow phosphors.

[en] Perfluorinated compounds (PFCs), especially the poly- and perfluorinated alkyl substances (PFASs), have drawn a lot attention due to their wide detection in the environment, wildlife, humans (Buck, 2011) and community outrage. PFASs are a family of chemical compounds composed of a carbon chain that can be linear or branched, and fully or partially fluorinated. They show high thermal, chemical and biochemical stability due to the strength of the carbon-fluorine bond (Renner, 2003). The characteristics that low aqueous surface tension and amphiphilic behaviour lead to their extensive use in surfactants, fire-fighting foams, food packing paper, textile, carpet and leather crafts since 1950s (Ghisi, 2018). Due to their sustainability and potential to be bioaccumulated in biota, recent research has focused intensively on their toxicity. It is also recognised that environmental background concentrations of PFASs, that influence the degree of contamination in food and water are the major source of human intake (Bizkarguenaga, 2016). As good is one of the major pathways of human exposure, the proposed study and this paper focusses on the influence of soil properties on PFASs bioaccumulation to different edible plant species. Bioconcentration factor (BAF) of three main PFCs (PFOS, PFOA and PFHxS) in the edible parts of three different plant species (spinach, lettuce and tomato) will be investigated using long-term field contaminated soils from six PFCs contaminated site. The relationship between soil properties, PFAS intensity and quantity factor would be examined using statistical analyses. (author)

[en] Two dipolar compounds with dipicolinate as electron acceptor group named trans-dimethyl-4-[4’-(N,N-dimethylamino)-styry1]-pyridin-2,6-dicarboxylate (M-1), trans-dimethyl-4-[4'-(N,N-diphenylamino)-styry1]-pyridin-2,6-dicarboxylate (P-1) as well as a P-1 based multi-branched octupolar compound {4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl) vinyl]}-N,N-bis{4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl)vinylphenyl]} aniline (P-3) with intense two-photon fluorescence emission properties are systematically investigated by using steady-state absorption and fluorescence spectroscopy, Z-scan, and two-photon excited fluorescence (TPF) method. The two-photon absorption cross section of octupolar compound P-3 in THF solution is determined to be 376 GM, which is approximately 12 times greater than that of dipolar counterpart P-1 (32 GM). Transient absorption spectroscopy is employed to investigate the excited state dynamics of the dipolar and octupolar compounds. The formation and relaxation lifetimes of the intra-molecular charge transfer (ICT) state are determined to be in the ranges of several picoseconds and several-hundreds of picoseconds, respectively, for all the three compounds in THF solutions. An extended π-conjugated system and increased intra-molecular cooperative effect are responsible for the observed large two-photon absorption character. - Highlights: • Octupolar compound gain 12-fold enhancement of two photon absorption. • Dynamic properties of intra-molecular charge transfer state are determined. • Cooperative effect is responsible for great increase of two photon character.