Pd-Catalyzed Regioselective Hydroformylation of Olefins with HCO2H and Its Derivatives.

An effective Pd-catalyzed regioselective hydroformylation process with N-formylsaccharin or 2,4,6-trichlorophenyl formate along with formic acid is described. Linear aldehydes can be obtained in up to 83% yield and >20:1 l/b ratio. The reaction is operationally simple without the need for external CO and H2.

Offline and online basic need satisfaction and smartphone use behaviors: A mediation model.

Based on the self-determination theory, this study compared the offline and online need satisfaction during the COVID-19 period and investigated how the fulfilment experienced in the different settings affected an individual's smartphone use outcomes. 546 Chinese undergraduate students participated in the study and were measured with their levels of offline and online basic need satisfaction, smartphone use patterns, and problematic smartphone use. The results showed that offline basic need satisfaction negatively predicted problematic smartphone use via the information seeking pattern, whereas online basic need satisfaction positively predicted problematic smartphone use via the use patterns of transaction and entertainment. Our study expands the research scope of the pertinent topic and pinpoints the mechanism between the basic need satisfaction and problematic smartphone use.

Resilience and problematic smartphone use: a moderated mediation model.

BACKGROUND: Problematic smartphone use (PSU) is adversely correlated with resilience. To completely comprehend the mechanism underlying this relationship, however, more investigation is required. METHODS: For this cross-sectional study, the method of stratified random cluster sampling was applied. 834 Chinese undergraduate students (aged 17 to 24) were recruited, and self-reported questionnaires were administered to measure their levels of resilience, perceived social support, the sense of school belonging, and habitual and problematic smartphone use. RESULTS: The findings showed that resilience both directly and indirectly predicted PSU through perceived social support and the sense of school belonging. Additionally, there were significant moderating effects of habitual smartphone use between resilience and perceived social support, the sense of school belonging, and PSU. CONCLUSIONS: Our research identified the negative influence of resilience on PSU, and specifically, highlighted the mediation effects of perceived social support and the sense of school belonging. Of significance, we also found the moderation effect of habitual smartphone use in the development of PSU.

Stress, academic burnout, smartphone use types and problematic smartphone use: The moderation effects of resilience.

Few studies have investigated stress in association with social and process smartphone use and how these types of use influence problematic smartphone use during the COVID-19 pandemic; furthermore, the moderation effects of resilience have been rarely tested in this model. For these, a cross-sectional survey was conducted involving 766 Chinese undergraduate students (74.4% female; M = 20.1 years, SD = 1.15) who were measured with their levels of stress, academic burnout, smartphone use types (social/process smartphone use), resilience, and problematic smartphone use. Based on the I-PACE theory, we built a structural equation model, and the results indicated that compared with social smartphone use, process smartphone use more related to problematic smartphone use; academic burnout fully mediated between stress and process smartphone use, and between stress and problematic smartphone use. Moreover, resilience moderated between stress and academic burnout, between academic burnout and process smartphone use, and between academic burnout and problematic smartphone use. We discuss the process smartphone use as a key indicator of problematic smartphone use and the role of academic burnout for linking stress and smartphone use behaviors. In addition, interventions for enhancing resilience should be launched in the future.

Morphological Attractors in Natural Convective Dissolution.

Recent experiments demonstrate how a soluble body placed in a fluid spontaneously forms a dissolution pinnacle-a slender, upward pointing shape that resembles naturally occurring karst pinnacles found in stone forests. This unique shape results from the interplay between interface motion and the natural convective flows driven by the descent of relatively heavy solute. Previous investigations suggest these structures to be associated with shock formation in the underlying evolution equations, with the regularizing Gibbs-Thomson effect required for finite tip curvature. Here, we find a class of exact solutions that act as attractors for the shape dynamics in two and three dimensions. Intriguingly, the solutions exhibit large but finite tip curvature without any regularization, and they agree remarkably well with experimental measurements. The relationship between the dimensions of the initial shape and the final state of dissolution may offer a principle for estimating the age and environmental conditions of geological structures.

Academic Burnout and Problematic Smartphone Use During the COVID-19 Pandemic: The Effects of Anxiety and Resilience.

Background: Academic burnout has been associated with problematic smartphone use. However, the mechanism underlying this relation has been inadequately explored during the COVID-19 pandemic. Materials and Methods: A total of 748 Chinese undergraduate students were recruited in the study who were measured with their levels of academic burnout, anxiety, resilience, and problematic smartphone use. Results: Our study showed that academic burnout significantly predicted problematic smartphone use both directly and indirectly via anxiety. By constructing a moderated mediation model, our study found that resilience moderated the direct impact and the second half of the indirect path (between anxiety and problematic smartphone use); however, with the moderation effects of resilience, both the indirect impact of academic burnout on problematic smartphone use via anxiety became insignificant. Conclusions: Our findings brought additional evidence on the association between academic burnout and problematic smartphone use and significantly suggested the potential solution to alleviate the influences.

Depression and anxiety symptoms are associated with problematic smartphone use under the COVID-19 epidemic: The mediation models.

COVID-19 epidemic has brought wide psychological impacts on the young adults. To investigate the depression and anxiety symptoms and their associations with problematic smartphone use under the COVID-19 epidemic, a total of 847 Chinese undergraduate students joined in this study and were measured with their levels of depression and anxiety symptoms, resilience, perceived social support, the sense of school belonging and problematic smartphone use. Results showed that among the Chinese undergraduate students, the disorder rates of depression and anxiety symptoms were 29.16% and 46.64% respectively, and their symptoms ranged from mild to extreme severe. Depression and anxiety symptoms both positively predicted problematic smartphone use. Resilience, perceived social support and the sense of school belonging partially mediated both associations; resilience and the sense of school belonging exerted buffering effects, while perceived social support exacerbated the impacts. The current study advanced our understanding of the COVID-19 impacts and furthermore, suggested the protective factors for mitigating these impacts.

Ultra-sharp pinnacles sculpted by natural convective dissolution.

The evolution of landscapes, landforms, and other natural structures involves highly interactive physical and chemical processes that often lead to intriguing shapes and recurring motifs. Particularly intricate and fine-scale features characterize the so-called karst morphologies formed by mineral dissolution into water. An archetypal form is the tall, slender, and sharply tipped karst pinnacle or rock spire that appears in multitudes in striking landforms called stone forests, but whose formative mechanisms remain unclear due to complex, fluctuating, and incompletely understood developmental conditions. Here, we demonstrate that exceedingly sharp spires also form under the far-simpler conditions of a solid dissolving into a surrounding liquid. Laboratory experiments on solidified sugars in water show that needlelike pinnacles, as well as bed-of-nails-like arrays of pinnacles, emerge robustly from the dissolution of solids with smooth initial shapes. Although the liquid is initially quiescent and no external flow is imposed, persistent flows are generated along the solid boundary as dense, solute-laden fluid descends under gravity. We use these observations to motivate a mathematical model that links such boundary-layer flows to the shape evolution of the solid. Dissolution induces these natural convective flows that, in turn, enhance dissolution rates, and simulations show that this feedback drives the shape toward a finite-time singularity or blow-up of apex curvature that is cut off once the pinnacle tip reaches microscales. This autogenic mechanism produces ultra-fine structures as an attracting state or natural consequence of the coupled processes at work in the closed solid-fluid system.

The role of shape-dependent flight stability in the origin of oriented meteorites.

The atmospheric ablation of meteoroids is a striking example of the reshaping of a solid object due to its motion through a fluid. Motivated by meteorite samples collected on Earth that suggest fixed orientation during flight-most notably the conical shape of so-called oriented meteorites-we hypothesize that such forms result from an aerodynamic stabilization of posture that may be achieved only by specific shapes. Here, we investigate this issue of flight stability in the parallel context of fluid mechanical erosion of clay bodies in flowing water, which yields shapes resembling oriented meteorites. We conduct laboratory experiments on conical objects freely moving through water and fixed within imposed flows to determine the dependence of orientational stability on shape. During free motion, slender cones undergo postural instabilities, such as inversion and tumbling, and broad or dull forms exhibit oscillatory modes, such as rocking and fluttering. Only intermediate shapes, including the stereotypical form carved by erosion, achieve stable orientation and straight flight with apex leading. We corroborate these findings with systematic measurements of torque and stability potentials across cones of varying apex angle, which furnish a complete map of equilibrium postures and their stability. By showing that the particular conical form carved in unidirectional flows is also posturally stable as a free body in flight, these results suggest a self-consistent picture for the origin of oriented meteorites.