Instability, changes, and internal structure of children's attitudes toward mathematics in primary school: A four-wave investigation.

The longitudinal person-oriented study aimed to explore profiles, stability, gender differences, and compositional relations of math attitudes by tracking Chinese third graders (Ntotal = 1013, Mage(T1) = 8.92 ± 0.46, Ngirls = 404) in four waves with 1-year intervals. Five profiles and unstable transitional probabilities were identified among the four waves. The relations between enjoyment to confidence and value shifted from reciprocity to enjoyment dominance, but value negatively predicted later enjoyment and confidence. Additionally, boys' advantages were significant in late elementary school (fifth, sixth grades) and girls benefited from initial positive attitudes. These findings suggest that Chinese students' math attitudes in middle childhood are unstable, shaped by internal and external environmental dynamics, and need to be further explored in cross-cultural research.

Math attitudes and math anxiety predict students' perception of teacher support in primary school, but not vice versa.

BACKGROUND: Both teacher support and math attitudes have been identified as associated with math anxiety in primary school children. However, little is known about how they are interrelated longitudinally. AIMS: The study was designed to examine the associations among perceived teacher support, math attitudes, and math anxiety in Chinese primary school students. SAMPLE: The sample included 1802 students (56.16% boys) initially in the third and fourth grades in two public schools in China. METHODS: A three-year cross-lagged panel design was conducted to examine the associations among perceived teacher support, math attitudes, and math anxiety. Moreover, a multigroup analysis was used to examine whether the associations varied by gender. RESULTS: There were reciprocal associations over time between math attitudes and math anxiety. Meanwhile, both math attitudes and math anxiety significantly predicted perceived teacher support one year later, but not vice versa. Further, the association between T1 math anxiety and T3 perceived teacher support was mediated by T2 math attitudes; the association between T1 math attitudes and T3 perceived teacher support, on the other hand, was mediated by T2 math anxiety. Moreover, there were no significant gender differences in these associations. CONCLUSIONS: Math anxiety and math attitudes objectively affected each other, and both of them significantly predicted later perceived teacher support, but not vice versa. This study demonstrates that children are not merely passive recipients of environmental influences and offers theoretical guidance for intervention practices that aim to reduce the risk of math anxiety.

The Consistence of Dynamic Contrast-Enhanced MRI and Filter-Exchange Imaging in Measuring Water Exchange Across the Blood-Brain Barrier in High-Grade Glioma.

BACKGROUND: Water exchange across blood-brain barrier (BBB) (WEXBBB ) is an emerging biomarker of BBB dysfunction with potential applications in many brain diseases. Several MRI methods have been proposed to measure WEXBBB , but evidence remains scarce whether different methods can produce comparable WEXBBB . PURPOSE: To explore whether dynamic contrast-enhanced (DCE)-MRI and vascular water exchange imaging (VEXI) could produce comparable WEXBBB in high-grade glioma (HGG) patients. STUDY TYPE: Prospective cross-sectional. SUBJECTS: 13 HGG patients (58.4 ± 9.4 years, 9 females, 4 WHO III and 9 WHO IV). FIELD STRENGTH/SEQUENCE: A 3 T, spoiled gradient-recalled-echo DCE-MRI and VEXI containing two pulsed-gradient spin-echo blocks separated by a mixing block. ASSESSMENTS: The enhanced tumor and contralateral normal-appearing white matter (cNAWM) volume-of-interests (VOIs) were drew by two neuroradiologists. And whole-brain NAWM and normal-appearing gray matter (NAGM) without tumor-affected regions were segmented by automated segmentation algorithm in FSL. STATISTICAL TESTS: Student's t-test was used to evaluate parameters difference between cNAWM and tumor, NAGM and NAWM, respectively. The correlation between vascular water efflux rate constant (kbo ) from DCE-MRI and apparent exchange rate across BBB (AXRBBB ) from VEXI was evaluated by Pearson correlation. P < 0.05 was considered statistically significant. RESULTS: Compared with cNAWM, both kbo and AXRBBB were significantly reduced in tumor (kbo = 3.50 ± 1.18 sec-1 vs. 1.03 ± 0.75 sec-1 ; AXRBBB = 3.54 ± 1.11 sec-1 vs. 1.94 ± 1.04 sec-1 ). Both kbo and AXRBBB showed significantly higher values in NAWM than NAGM (kbo = 3.50 ± 0.59 sec-1 vs. 2.10 ± 0.56 sec-1 ; AXRBBB = 3.35 ± 0.77 sec-1 vs. 2.07 ± 0.52 sec-1 ). The VOI-averaged kbo and AXRBBB were also linearly correlated in tumor, NAWM, and NAGM (r = 0.59). DATA CONCLUSION: DCE-MRI and VEXI showed comparable and correlated WEXBBB in HGG patients, suggesting that the consistence and reliability of these two MRI methods in measuring WEXBBB . EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 1.

3D Simulations of Freezing Characteristics of Double-Droplet Impact on Cold Surfaces with Different Wettability.

In this work, the freezing characteristics of double-droplet impact on three typical wettability surfaces were investigated by coupling the solidification and melting VOF models. Different temperature conditions were adopted to study the influence of icing speed on droplet behavior. Simulation results show that the motion of the double-droplet impact is consistent with that of a single droplet in the early spreading stage but behaves differently in the retraction stage. The wetting area evolution during the impact-freezing process shows different tendency for hydrophilic and hydrophobic surfaces: Compared with single droplets, double droplets have a smaller wetting area factor on hydrophilic surfaces but a larger one on superhydrophobic surfaces. In addition, three typical impact results are observed for the double-droplet impact on a superhydrophobic cold surface: full rebound, adhesive avulsion, and full adhesion, which reflects the interaction of droplet merging and solidification during the impact freezing of the double droplet. These findings may deepen our understanding of the mechanism of impact freezing on a cold surface, it provides reference for the associated applications and technologies in icing/anti-icing.

Research on a tunable monochromatic X-rays source in (5∼40) keV.

The monochromatic X-rays produced by Bragg diffraction has the advantage of continuously adjustable energy, which is the preferred scheme to realize the monochromatic X-rays. In order to establish a (5-40) keV monochromatic X-rays facility, the Bragg diffraction of crystal monochromator is studied. The position of the emitted X-rays beam is required to remain unchanged when the Bragg angle is adjusted to accurately calibrate the detection efficiency. The monochromatic X-rays calibration facility is mainly composed of an X-rays tube, diffraction crystal and synchronous rotating device, which could cover the energy range of (5-40) keV. A new mechanical structure was invented to realize the linkage between crystal and X-rays tube. When the Bragg angle of crystal is adjusted at θ, the X-ray source will rotate at 2θ angle, and the position of the monochromatic X-rays beam will remain unchanged. Based on the Monte Carlo simulation program, the geometric structure model of silicon drift detector is established. The structure of the detector is optimized according to the experimental conditions and the material size of the shell, window and crystal of the detector. The accurate and reliable detector model is obtained. The response of the detector to different energy under the parallel X-rays source is calculated, and the detection efficiency curve is obtained. The detection efficiency is calibrated by using standard radiation source to ensure the accuracy of photon flux measurement. The energy range, flux, monochromaticity and spot distribution of the monochromatic X-rays radiation device are measured.

Physical Simulation Model of WO3 Electrochromic Films Based on Continuous Electron-Transfer Kinetics and Experimental Verification.

Tungsten oxide (WO3) electrochromic devices have attracted a lot of interest in the energy conservation field and have shown a preliminary application potential in the market. However, it is difficult to quantitatively direct experiments with the existing electrochromic theoretical models, which can restrict the further development of electrochromism. Here, an electrochromic physical simulation model of WO3 films was built to solve the above problem. Experimentally, the actual electrochromic kinetics of WO3 in the LiClO4/propylene carbonate electrolyte was determined as a continuous electron-transfer process by cyclic voltammetry measurement and X-ray photoelectron spectroscopy analysis. Theoretically, the continuous electron-transfer process, Li+-ion diffusion process, and the transmittance change process were described by a modified Butler-Volmer equation, Fick's law, and charge versus coloration efficiency/bleaching efficiency coupling equation, respectively. The comparisons between theoretical and experimental data were conducted to verify this model. The shape of the simulated current curves was basically consistent with that of experiments. Besides, the difference of transmittance between the simulation and experiments was less than 8%. The difference between theory and experiment was attributed to the influence of the electric double layer and the actual reaction interface. The success of the simulation was attributed to the accurate description of the electrochromic process by continuous electron-transfer kinetics. This model can be applied in the research of electrochromic mechanisms, experimental result prediction, and novel device development due to its clear physical nature.

Effect of the Ammonium Tungsten Precursor Solution with the Modification of Glycerol on Wide Band Gap WO3 Thin Film and Its Electrochromic Properties.

Tungsten trioxide (WO3) is a wide band gap semiconductor material, which is commonly not only used, but also investigated as a significant electrochromic layer in electrochromic devices. WO3 films have been prepared by inorganic and sol-gel free ammonium tungstate ((NH4)2WO4), with the modification of glycerol using the spin coating technique. The surface tension, the contact angle and the dynamic viscosity of the precursor solutions demonstrated that the sample solution with a 25% volume fraction of glycerol was optimal, which was equipped to facilitate the growth of WO3 films. The thermal gravimetric and differential scanning calorimetry (TG-DSC) analysis represented that the optimal sample solution transformed into the WO3 range from 220 °C to 300 °C, and the transformation of the phase structure of WO3 was taken above 300 °C. Fourier transform infrared spectroscopy (FT-IR) spectra analysis indicated that the composition within the film was WO3 above the 300 °C annealing temperature, and the component content of WO3 was increased with the increase in the annealing temperature. The X-ray diffraction (XRD) pattern revealed that WO3 films were available for the formation of the cubic and monoclinic crystal structure at 400 °C, and were preferential for growing monoclinic WO3 when annealed at 500 °C. Atomic force microscope (AFM) images showed that WO3 films prepared using ammonium tungstate with modification of the glycerol possessed less rough surface roughness in comparison with the sol-gel-prepared films. An ultraviolet spectrophotometer (UV) demonstrated that the sample solution which had been annealed at 400 °C obtained a high electrochromic modulation ability roughly 40% at 700 nm wavelength, as well as the optical band gap (Eg) of the WO3 films ranged from 3.48 eV to 3.37 eV with the annealing temperature increasing.