Retrieval practice may not benefit mathematical word-problem solving.

The retrieval practice effect refers to the fact that one or even multiple retrievals of memory content during the same period are more effective than repeated studying to promote future memory retention. It is effective for numerous declarative knowledge learning materials. However, studies have demonstrated that retrieval practice does not benefit problem-solving skill learning. This study used worked examples from math word problem tasks as learning materials, considering the retrieval difficulty as the main factor. Experiment 1 explored the effect of retrieval practice on acquiring problem-solving skills under different initial testing difficulties. Experiment 2 manipulated the difficulty of materials as a variable to ascertain the effect of retrieval practice on problem-solving skills under different material difficulty levels. Experiment 3 introduced feedback variables to facilitate the generation of the retrieval practice effect and examined the effects of various difficulty feedback levels on problem-solving skills learning. Results showed that, compared with restudying examples (SSSS), the example-problem pairs (STST) did not promote delayed test performance. As for the retrieval practice effect, as no differences or advantages were found in the repeated study group on the immediate test, the retrieval practice group generally outperformed the repeated study group on the delayed test. However, across the three experiments, we found no evidence of retrieval practice affecting results during an enhanced delayed test. Therefore, there may be no retrieval practice effect on acquiring problem-solving skills from worked examples.

Impact of the COVID-19 epidemic anxiety on college students' employment confidence and employment situation perception in China.

The psychological problems and employment problems of college students have always been the focus of attention of all sectors of society. The COVID-19 epidemic has a great impact on the mental health and employment of Chinese college students. Under this background, this study discusses how epidemic anxiety affects the employment confidence and perception of employment situation of Chinese college students. Through the online questionnaire survey of 1,132 college students nationwide, and the ordinal logistic regression analysis of the survey data using Stata 16.0 software, the results show that: (1) Epidemic anxiety negatively affects Chinese college students' employment confidence and employment situation perception, and has a significant impact on employment confidence. The three control variables of employment guidance, older age and higher education have a significant positive impact on college students' employment confidence and employment situation perception. College students in the eastern region have stronger employment confidence and more optimistic employment situation perception. But the expected monthly salary is negatively correlated with employment confidence. (2) Male college students and Science and Engineering students' epidemic anxiety have a stronger negative impact on employment confidence and employment situation perception. (3) Employment guidance has a moderating effect on the relationship between epidemic anxiety, employment confidence and employment situation perception. Employment guidance can enhance college students' employment confidence and reduce their sense of employment crisis by alleviating epidemic anxiety. Combined with the research conclusions, it is proposed that the state and schools should pay attention to the psychological counseling of college students, strengthen the employment guidance of colleges and universities, vigorously support the development of small, medium-sized and micro enterprises, and improve the employment and entrepreneurship service system of college students, so as to promote the employment of college students.

A simple "turn-on" fluorescence sensor for salicylaldehyde skeleton based on switch of PET-AIE effect.

The selective detection of salicylaldehyde skeleton is of great significance in phytochemistry and biological research but rarely reported. In this research, a simple and highly selective "turn-on" fluorescence sensor (CDB-Am) for salicylaldehyde skeleton was developed based on switch of photoinduced electron transfer (PET) and aggregation-induced emission (AIE). CDB-Am bearing amino-cyanodistyrene structure responded to salicylaldehyde in the range of 3.1 to 40 µM with a detection limit of 0.94 µM. The sensing process of formation of Schiff-base adduct CDB-SA was confirmed by 1H NMR, MS, and FT-IR spectra, revealing that a recovered AIE property accounted for the turn-on fluorescence response of CDB-Am and the intramolecular hydrogen bonding played a crucial role in the disruption of PET process. This sensing ability was successfully applied for both fluorescence qualitative test of salicylaldehyde skeleton on TLC analysis and quantitative detection of salicylaldehyde skeleton with good accuracy in the root bark of Periploca sepium, suggesting the extensive applications in phytochemistry and traditional Chinese herbal medicine. Furthermore, CDB-Am exhibited the first excellent fluorescence imaging ability in detecting salicylaldehyde skeleton in a living system. This work supplied a new strategy of preparing a novel "turn-on" fluorescence probe for detecting salicylaldehyde skeleton in complex environments and living bodies.

A first porphyrin liquid crystal with strong fluorescence in both solution and aggregated states based on the AIE-FRET effect.

Porphyrins are good near-infrared fluorescent materials, but the strong self-assembly stacking resulted in the aggregation-caused quenching (ACQ) effect, limiting their emissive performance in aggregated states. In this work, a novel diphenylacrylonitrile-porphyrin derivative with multiple polyglycol chains on the periphery was designed and synthesized as an excellent near-infrared-emissive liquid crystalline material in both solution and aggregated states, which was first observed for porphyrin liquid crystals. It exhibited a high self-assembly ability with the ordered hexagonal columnar mesophase between 70 and 120 °C approximately. The strong AIE-FRET effect was produced based on the overlap of the emission wavelength of diphenylacrylonitrile and the absorption wavelength of the porphyrin, resulting in the excellent near-infrared emission in both solution and aggregated states. The pseudo Stokes shift was as large as 210 nm and the fluorescence quantum yield reached 0.12 in the solid state. Moreover, this porphyrin liquid crystal displayed low biotoxicity and excellent fluorescence bio-imaging ability in living cells, opening a new application prospect for porphyrin liquid crystalline materials.

Protection zone in a diffusive predator-prey model with Beddington-DeAngelis functional response.

In any reaction-diffusion system of predator-prey models, the population densities of species are determined by the interactions between them, together with the influences from the spatial environments surrounding them. Generally, the prey species would die out when their birth rate is too low, the habitat size is too small, the predator grows too fast, or the predation pressure is too high. To save the endangered prey species, some human interference is useful, such as creating a protection zone where the prey could cross the boundary freely but the predator is prohibited from entering. This paper studies the existence of positive steady states to a predator-prey model with reaction-diffusion terms, Beddington-DeAngelis type functional response and non-flux boundary conditions. It is shown that there is a threshold value [Formula: see text] which characterizes the refuge ability of prey such that the positivity of prey population can be ensured if either the prey's birth rate satisfies [Formula: see text] (no matter how large the predator's growth rate is) or the predator's growth rate satisfies [Formula: see text], while a protection zone [Formula: see text] is necessary for such positive solutions if [Formula: see text] with [Formula: see text] properly large. The more interesting finding is that there is another threshold value [Formula: see text], such that the positive solutions do exist for all [Formula: see text]. Letting [Formula: see text], we get the third threshold value [Formula: see text] such that if [Formula: see text], prey species could survive no matter how large the predator's growth rate is. In addition, we get the fourth threshold value [Formula: see text] for negative [Formula: see text] such that the system admits positive steady states if and only if [Formula: see text]. All these results match well with the mechanistic derivation for the B-D type functional response recently given by Geritz and Gyllenberg (J Theoret Biol 314:106-108, 2012). Finally, we obtain the uniqueness of positive steady states for [Formula: see text] properly large, as well as the asymptotic behavior of the unique positive steady state as [Formula: see text].

A novel and label-free immunosensor for bisphenol A using rutin as the redox probe.

In this work, a new and label-free electrochemical immunosensor for sensitive detection of bisphenol A was reported. MWCNTs and gold nanoparticles (AuNPs) were modified on glassy carbon electrode surface to enhance current response. The Anti-BPA was immobilized on the modified electrode through AuNPs. Rutin was used for the first time as the redox probe to construct electrochemical immunosensor of bisphenol A. The peak current change due to the specific immuno-interaction between anti-BPA and BPA on the modified electrode surface was utilized to detect bisphenol A. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) were employed to trace the assembly process of the electrochemical immunosensor. Experimental factors affecting the sensitivity of the immunosensor were examined in terms of incubation time and pH of phosphate buffer solution (PBS). Under optimized conditions, the linear range of calibration curve based on the relationship between current response and BPA concentration was from 1.0×10(-8)-1.0×10(-6)M with detection limit of 8.7×10(-9)M (S/N=3). The proposed immunosensor showed good reproducibility, selectivity, stability and was successfully applied to the determination of BPA in real sample.

High carbohydrate intake from starchy foods is positively associated with metabolic disorders: a Cohort Study from a Chinese population.

Starchy foods are the main sources of carbohydrates; however, there is limited information on their metabolic impact. Therefore, we assessed the association between carbohydrates from starchy foods (Carb-S) intakes and the metabolic disorders of metabolic syndrome (MetS) and hyperlipidemia. In this study, 4,154 participants from Northern China were followed up for 4.2 years. Carb-S included rice, refined wheat, tubers, and their products. Multivariable regression models were used to calculate risk ratios (RRs) for MetS and hyperlipidemia from Carb-S, total carbohydrates, and carbohydrates from other food sources (Carb-O). Receiver operating characteristic analysis was used to determine a Carb-S cut-off value. High total carbohydrate intake was associated with increased risks of MetS (RR: 2.24, 95% CI: 1.00-5.03) and hyperlipidemia (RR: 3.05, 95% CI: 1.25-7.45), compared with the first quartile. High Carb-S intake (fourth quartile) was significantly associated with MetS (RR: 1.48, 95% CI: 1.01-2.69) and hyperlipidemia (RR: 1.73, 95% CI: 1.05-3.35). No associations with Carb-O were observed. Visceral adiposity, triglyceride levels, and high-density lipoprotein cholesterol significantly contributed to the metabolic disorders. The Carb-S cut-off value was 220 g. Both high total carbohydrate and Carb-S intakes were associated with hyperlipidemia and MetS; Carb-S appears to contribute more to these disorders.

Weight loss, inflammatory markers, and improvements of iron status in overweight and obese children.

OBJECTIVE: To assess the effect of a weight-loss program on improving iron status in overweight and obese school-aged children. STUDY DESIGN: The data were analyzed in overweight and obese children (7-11 years of age; 114 girls and 212 boys) with body mass index-for-age z-scores (BAZ) >1 from a weight-loss program. Schools were randomly divided into 2 groups: intervention and control. Children in the intervention group underwent a 1-year, nutrition-based comprehensive intervention weight-loss program. Anthropometric, dietary intake, and physical activity data were collected at baseline and follow-up (1 year). Iron status and inflammatory markers were assessed within a month. RESULTS: In the intervention group, BAZ decreased more than that in the control group (-0.4 ± 0.7 vs -0.1 ± 0.6, P < .0001); and iron profiles and inflammation status were improved at follow-up. In multivariable linear regression models, a greater decrease of BAZ and inflammation factors predicted a better improvement of iron status. After adjustment of ΔBAZ, ΔC-reactive protein was significantly associated with Δserum ferritin (ß: 1.89; 95% CI, 0.70-3.09; P = .002) and Δsoluble transferrin receptor (ß: 0.88; 95% CI, 0.16-0.59; P = .017); Δinterleukin-6 was significantly associated with Δserum ferritin (ß: 1.22; 95% CI, 0.64-1.79; P < .0001). CONCLUSIONS: Iron status and inflammation were improved by weight reduction. The improvement in inflammatory markers during weight reduction was independently associated with improvements of iron status.

[Photoinduced intra-molecular energy transfer of a novel phthalocyanine zinc(II) bearing poly (aryl benzyl ether) dendritic substitutents with carboxylic terminal].

The photoinduced intra-molecular energy transfer in phthalocyanine zinc(II) bearing poly (aryl benzyl ether) dendritic substituents with carboxylic terminal was studied by steady-state, time-resolved fluorescence and UV/Vis spectroscopic methods. The result shows that the complexes mainly existed as monomers in dimethyl sulfoxide. The light-harvesting ability of this series of dendritic phthalocyanines increased with the dendron generation under 270 nm. The effects of the dendron generation on the fluorescence characteristics of phthalocyanine cores was significantly, and the fluorescence lifetime and fluorescent quantum yield decreased with the increase of the dendron generation. Intra-molecular energy could be transferred from peripheral dendron acting as an energy hydrazine to the phthalocyanine core during a photo-induced process. With the dendrimer increasing, the intra-molecular energy transfer quantum yield increased. These results obviously indicated that this series of dendritic phthalocyanines is a king of novel compound with light-harvesting structure.