<i>C</i>₄(<i>L</i>_<i>x</i>, <i>e</i>; <i>l</i>) and estimated values.

<p><i>C</i>₄(<i>L</i>_<i>x</i>, <i>e</i>; <i>l</i>) and estimated values.</p

Test multivariate nonlinear Granger causality form <i>Y</i>_<i>t</i> to <i>X</i>_<i>t</i>.

<p>Test multivariate nonlinear Granger causality form <i>Y</i>_<i>t</i> to <i>X</i>_<i>t</i>.</p

Descriptive statistics of the series <i>Y</i>_1<i>t</i>, <i>Y</i>_2<i>t</i>, <i>X</i>_1<i>t</i> and <i>X</i>_2<i>t</i>.

<p>Descriptive statistics of the series <i>Y</i>_1<i>t</i>, <i>Y</i>_2<i>t</i>, <i>X</i>_1<i>t</i> and <i>X</i>_2<i>t</i>.</p

Testing nonlinear causality from prices to trading volumes of China’s A shares.

<p>Testing nonlinear causality from prices to trading volumes of China’s A shares.</p

Improving the Sensitivity and Linear Range of Photoionization Ion Mobility Spectrometry via Confining the Ion Recombination and Space Charge Effects Assisted by Theoretical Modeling

Photoionization (PI) is an efficient ionization source for ion mobility spectrometry (IMS) and mass spectrometry. Its hyphenation with IMS (PI-IMS) has been employed in various on-site analysis scenarios targeting a wide range of compounds. However, the signal intensity and linear dynamic range of PI-IMS at ambient pressure usually do not follow the Beer–Lambert law predictions, and the factors causing that negative deviation remain unclear. In this work, a variable pressure PI-IMS system was developed to examine the ion loss effects from factors like ion recombination and space charge by varying its working pressure from 1 to 0.1 bar. Assisted by theoretical modeling, it was found that ion recombination could contribute up to 90% of signal intensity loss for ambient pressure PI-IMS setups. Lowering the pressure and increasing the electric field in PI-IMS helped suppress the ion recombination process and thus an optimal pressure Poptimal appeared for best signal intensity, despite the decreased net ion number density and the increased space charge effect. A simplified theoretical equation taking ion recombination as the primary ion loss factor was derived to link Poptimal with analyte concentration and electric field in PI-IMS, enabling a swift optimization of the PI-IMS performance. For example, compared to ambient pressure, PI-IMS at a Poptimal of 0.4 bar provided a signal intensity increment of more than 400% for 0.716 ppmv toluene and also expanded the linear dynamic range by more than two times. Revealing factors influencing the PI-IMS response would also benefit the applications of other chemical ionization sources in IMS or mass spectrometry (MS)

Dopant-Assisted Positive Photoionization Ion Mobility Spectrometry Coupled with Time-Resolved Thermal Desorption for On-Site Detection of Triacetone Triperoxide and Hexamethylene Trioxide Diamine in Complex Matrices

Peroxide explosives, such as triacetone triperoxide (TATP) and hexamethylene trioxide diamine (HMTD), were often used in the terrorist attacks due to their easy synthesis from readily starting materials. Therefore, an on-site detection method for TATP and HMTD is urgently needed. Herein, we developed a stand-alone dopant-assisted positive photoionization ion mobility spectrometry (DAPP-IMS) coupled with time-resolved thermal desorption introduction for rapid and sensitive detection of TATP and HMTD in complex matrices, such as white solids, soft drinks, and cosmetics. Acetone was chosen as the optimal dopant for better separation between reactant ion peaks and product ion peaks as well as higher sensitivity, and the limits of detection (LODs) of TATP and HMTD standard samples were 23.3 and 0.2 ng, respectively. Explosives on the sampling swab were thermally desorbed and carried into the ionization region dynamically within 10 s, and the maximum released concentration of TATP or HMTD could be time-resolved from the matrix interference owing to the different volatility. Furthermore, with the combination of the fast response thermal desorber (within 0.8 s) and the quick data acquisition software to DAPP-IMS, two-dimensional data related to drift time (TATP: 6.98 ms, <i>K</i>₀ = 2.05 cm² V^–1 s^–1; HMTD: 9.36 ms, <i>K</i>₀ = 1.53 cm² V^–1 s^–1) and desorption time was obtained for TATP and HMTD, which is beneficial for their identification in complex matrices

Additional file 3 of A comparative study of the prevalence of myopia and behavioral changes in primary school students

Additional file 3: Supplementary Table 2. Comparison ofbehaviors related to myopia between boys or girls in two group

Tailoring the Fluorescence of AIE-Active Metal–Organic Frameworks for Aqueous Sensing of Metal Ions

A hydroxyl-functionalized ligand was designed for the construction of metal–organic framework (MOF) materials with the aggregation-induced emission (AIE) feature, in which the fluorescence can be deliberately tailored: quenching the fluorescence to an “off” state by the decoration with heterocyclic auxiliary ligand 4,4′-bypyridine (Bpy) in the framework as a quenching agent and triggering the enhanced fluorescence to an “on” state by removal of Bpy through the metal competitive coordination substitution strategy. Our study shows that the occurrence of exciton migration between the AIE linker and conjugated auxiliary ligand Bpy causes fluorescence quenching. Time-dependent density functional theory was employed to understand the photoinduced electron transfer process and explain the origins of fluorescence quenching. Using this strategy, the prepared MOF material can perform as a fluorescence “off–on” probe for highly sensitive detection of Al³⁺ in aqueous media. The hydroxyl group plays a crucial role in sensing as it can selectively chelate Al³⁺, which is directly related to the dissociation of nonfluorescent MOF and consequent activation of the AIE process

Additional file 1 of A comparative study of the prevalence of myopia and behavioral changes in primary school students

Additional file 1

Additional file 4 of A comparative study of the prevalence of myopia and behavioral changes in primary school students

Additional file 4: SupplementaryTable 3.Comparison of behaviorsrelated to myopia between the twoCohorts according to ag