Visible‐light‐induced radical decarboxylative functionalization of carboxylic acids and their derivatives has recently received considerable attention as a novel and efficient method to create CC ...and CX bonds. Generally, this visible‐light‐promoted decarboxylation process can smoothly occur under mild reaction conditions with a broad range of substrates and an excellent functional‐group tolerance. The radical species formed from the decarboxylation step can participate in not only single photocatalytic transformations, but also dual‐catalytic cross‐coupling reactions by combining photoredox catalysis with other catalytic processes. Recent advances in this research area are discussed herein.
Photo op: A novel functionalization reaction using visible‐light‐induced photoredox catalysis has recently been developed (see title). The formed radical species can participate in not only single photocatalytic transformations, but also dual‐catalytic reactions by combining photoredox catalysis with other catalytic methods. Recent advances in this research area are discussed herein.
The processing of poly(p‐phenylene terephthalamide) (PPTA) has long been a great challenge. This work reports a simple “monomers‐nanofibers‐macroscopic product” (MNM) hierarchical self‐assembly ...approach to build 3D all‐PPTA engineering materials. This approach mainly includes the preparation of polymerization‐induced aramid nanofibers (PANFs) from monomers and the fabrication of all‐PPTA materials from PANF hydrogel. Various 3D architectures, including simple solid bulks and sophisticated honeycombs (HCs), are obtained after the dehydration and shrinking of the PANF hydrogel. The tensile strength and compressive yield strength of PANF bulk are more than 62 and 90 MPa, respectively, which are comparable to typical engineering plastics. The compressive strength of PANF HC with a density of 360 kg m−3 is more than 24 MPa. The thermal stability of PANF bulk and PANF HC are as good as that of Kevlar fiber and almost no decomposition occurred before 500 °C in a nitrogen atmosphere. Furthermore, the MNM process is performed under mild conditions, without high temperature, high pressure, or corrosive solvent. The MNM process is a novel strategy for the processing of all aromatic polyamide materials with complex structures and high performances and would be another development since the breakthrough of liquid crystal spinning technology of PPTA.
A simple “monomers–nanofibers–macroscopic product” hierarchical self‐assembly approach for the preparation of all‐aramid bulk and honeycomb materials, which are difficult to process in traditional ways, is demonstrated. These products show excellent mechanical and thermal performance. This work is a breakthrough for the processing of high‐performance engineering polymer material, and the industrialization prospect of all‐aramid products deserves further study.
Abstract
Glucose electrolysis offers a prospect of value-added glucaric acid synthesis and energy-saving hydrogen production from the biomass-based platform molecules. Here we report that ...nanostructured NiFe oxide (NiFeO
x
) and nitride (NiFeN
x
) catalysts, synthesized from NiFe layered double hydroxide nanosheet arrays on three-dimensional Ni foams, demonstrate a high activity and selectivity towards anodic glucose oxidation. The electrolytic cell assembled with these two catalysts can deliver 100 mA cm
−2
at 1.39 V. A faradaic efficiency of 87% and glucaric acid yield of 83% are obtained from the glucose electrolysis, which takes place via a guluronic acid pathway evidenced by in-situ infrared spectroscopy. A rigorous process model combined with a techno-economic analysis shows that the electrochemical reduction of glucose produces glucaric acid at a 54% lower cost than the current chemical approach. This work suggests that glucose electrolysis is an energy-saving and cost-effective approach for H
2
production and biomass valorization.
We investigated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) environmental contamination in 2 rooms of a quarantine hotel after 2 presymptomatic persons who stayed there were ...laboratory-confirmed as having coronavirus disease. We detected SARS-CoV-2 RNA on 8 (36%) of 22 surfaces, as well as on the pillow cover, sheet, and duvet cover.
Psychological health problems, especially emotional disorders, are common among adolescents. The epidemiology of emotional disorders is greatly influenced by stressful events. This study sought to ...assess the prevalence rate and socio-demographic correlates of depressive and anxiety symptoms among Chinese adolescents affected by the outbreak of COVID-19. We conducted a cross-sectional study among Chinese students aged 12–18 years during the COVID-19 epidemic period. An online survey was used to conduct rapid assessment. A total of 8079 participants were involved in the study. An online survey was used to collect demographic data, assess students’ awareness of COVID-19, and assess depressive and anxiety symptoms with the Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder (GAD-7) questionnaire, respectively. The prevalence of depressive symptoms, anxiety symptoms, and a combination of depressive and anxiety symptoms was 43.7%, 37.4%, and 31.3%, respectively, among Chinese high school students during the COVID-19 outbreak. Multivariable logistic regression analysis revealed that female gender was the higher risk factor for depressive and anxiety symptoms. In terms of grades, senior high school was a risk factor for depressive and anxiety symptoms; the higher the grade, the greater the prevalence of depressive and anxiety symptoms. Our findings show there is a high prevalence of psychological health problems among adolescents, which are negatively associated with the level of awareness of COVID-19. These findings suggest that the government needs to pay more attention to psychological health among adolescents while combating COVID-19.
The increased social and economic burdens for osteoporosis-related fractures worldwide make the prevention of such injuries a major public health goal. Previous studies have reached mixed conclusions ...regarding the association between calcium, vitamin D, or combined calcium and vitamin D supplements and fracture incidence in older adults.
To investigate whether calcium, vitamin D, or combined calcium and vitamin D supplements are associated with a lower fracture incidence in community-dwelling older adults.
The PubMed, Cochrane library, and EMBASE databases were systematically searched from the inception dates to December 24, 2016, using the keywords calcium, vitamin D, and fracture to identify systematic reviews or meta-analyses. The primary randomized clinical trials included in systematic reviews or meta-analyses were identified, and an additional search for recently published randomized trials was performed from July 16, 2012, to July 16, 2017.
Randomized clinical trials comparing calcium, vitamin D, or combined calcium and vitamin D supplements with a placebo or no treatment for fracture incidence in community-dwelling adults older than 50 years.
Two independent reviewers performed the data extraction and assessed study quality. A meta-analysis was performed to calculate risk ratios (RRs), absolute risk differences (ARDs), and 95% CIs using random-effects models.
Hip fracture was defined as the primary outcome. Secondary outcomes were nonvertebral fracture, vertebral fracture, and total fracture.
A total of 33 randomized trials involving 51 145 participants fulfilled the inclusion criteria. There was no significant association of calcium or vitamin D with risk of hip fracture compared with placebo or no treatment (calcium: RR, 1.53 95% CI, 0.97 to 2.42; ARD, 0.01 95% CI, 0.00 to 0.01; vitamin D: RR, 1.21 95% CI, 0.99 to 1.47; ARD, 0.00 95% CI, -0.00 to 0.01. There was no significant association of combined calcium and vitamin D with hip fracture compared with placebo or no treatment (RR, 1.09 95% CI, 0.85 to 1.39; ARD, 0.00 95% CI, -0.00 to 0.00). No significant associations were found between calcium, vitamin D, or combined calcium and vitamin D supplements and the incidence of nonvertebral, vertebral, or total fractures. Subgroup analyses showed that these results were generally consistent regardless of the calcium or vitamin D dose, sex, fracture history, dietary calcium intake, and baseline serum 25-hydroxyvitamin D concentration.
In this meta-analysis of randomized clinical trials, the use of supplements that included calcium, vitamin D, or both compared with placebo or no treatment was not associated with a lower risk of fractures among community-dwelling older adults. These findings do not support the routine use of these supplements in community-dwelling older people.
The microcontinental blocks in the CAOB include the combined NE China blocks (comprising the Erguna, Xing'an, Songliao and Jimusi-Khanka blocks) in the eastern segment of the CAOB, the ...Kazakhstan-Yili-Central Tianshan and Junggar blocks in the western segment of the CAOB, and the Tuva-Mongolia blocks and Beishan block in the central segment of the CAOB. The basement in these microcontinental blocks mainly consists of Archean to Paleoproterozoic crystalline rocks and/or Meso-Neoproterozoic granitoids and metamorphic complexes, indicating that most of the so-called blocks in the CAOB can be regarded as microcontinental fragments. Zircon age spectra from the eastern segment of the CAOB reveal four age peaks at 495Ma, 780Ma, 1825Ma and 2600Ma, which is similar to those recorded in the central and western segments of the CAOB. In addition, evidence of the global ‘Grenvillian’ tectonic event at 1000Ma is also present in most blocks, indicating that the microcontinents in the CAOB have a common tectonic history. Furthermore, late Pan-African metamorphism at ~500Ma affects all the microcontinents in the CAOB, with this granulite-facies event forming a single metamorphic belt that extends for >1300km across NE China, and named the “NE China Khondalite Belt” in the eastern segment of the CAOB. There is also a corresponding >1000km-long Sayang–Baikal orogenic belt along the southern margin of the Siberia Craton. We propose that the microcontinents of the CAOB originated as part of Rodinia along the global Grenville Orogenic Belt (1100–750Ma). At 750–600Ma, after the break-up of Rodinia, the various microcontinental blocks were located along the margin of Gondwana, close to the South China and Tarim cratons. At ~600Ma, these blocks became detached from eastern Gondwana and, together with accreted complexes, drifted to the north (present-day co-ordinates) across the Paleo-Asian Ocean to the southern margin of the Siberia Craton, where collision took place during the late Pan-African.
Excessive structural resonance response in the acoustic vibration coupling environment can cause adverse consequences such as structural damage, local instability, and component failure. Accurately ...predicting the vibration response of instruments under external sound fields helps to avoid structural performance degradation or damage caused by vibration, and ensures the reliability and safety of the system, which is of great significance for the effective load of instrument equipment. This paper constructs a finite element boundary element equation for the acoustic vibration coupling problem, and adopts a series of optimization measures for it. In response to the low computational efficiency of finite element boundary element equations and their inability to meet the computational requirements of complex models, this paper introduces the acoustic vibration reciprocity theorem and the fast directional boundary element method to compensate for the aforementioned shortcomings. In addition, the study used the weighted residual method to construct a data exchange algorithm to ensure energy conservation during the transfer process. The research focuses on typical structures of spacecraft and conducts simulation analysis and application research on acoustic vibration coupling problems. The simulation showcases that the introduction of the reciprocity theorem markedly reduces the calculation time and memory occupied by the equation, with a required calculation time of 1.23 h and a data file size of approximately 299.56 MB generated by the calculation; The overall error of the data exchange process is below 10−4. Scanning frequency analysis is conducted on the surface and local openings of the model structure, and it is found that the displacement of the selected excitation point is in good agreement with the analytical solution. This study effectively reduces simulation time and memory requirements through the proposed strategy, ensures energy conservation data exchange algorithms, improves the reliability and safety of structural design, and has important practical value for evaluating the structural performance of key equipment such as spacecraft.
The study of stellar oscillations allows us to infer the properties of stellar interiors. Meanwhile, fundamental parameters such as mass and radius can be obtained by studying stars in binary ...systems. The synergy between binarity and asteroseismology can constrain the parameter space of stellar properties and facilitate the asteroseismic inference. On the other hand, binarity also introduces additional complexities such tides and mass transfer. From an observational perspective, we briefly review the recent advances in the study of tidal effects on stellar oscillations, focusing on upper main sequence stars (F-, A-, or OB- type). The effect can be roughly divided into two categories. The first one concerns the tidally excited oscillations (TEOs) in eccentric binaries where TEOs are mostly due to resonances between dynamical tides and gravity modes of the star. TEOs appear as orbital-harmonic oscillations on top of the eccentric ellipsoidal light curve variations (the “heartbeat” feature). The second category is regarding the self-excited oscillations perturbed by static tides in circularized and synchronized close binaries. It includes the tidal deformation of the propagation cavity and its effect on eigenfrequencies, eigenfunctions, and the pulsation alignment. We list binary systems that show these two types of tidal effect and summarize the orbital and pulsation observables. We also discuss the theoretical approaches used to model these tidal oscillations and relevant complications such as non-linear mode coupling and resonance locking. Further information can be extracted from the observations of these oscillations which will improve our understanding of tides. We also discuss the effect of mass transfer, the extreme result of tides, on stellar oscillations. We bring to the readers' attention: (1) oscillating stars undergoing mass accretion (A-, F-, and OB type pulsators and white dwarfs), for which the pulsation properties may be changed significantly by accretion; (2) post-mass transfer pulsators, which have undergone a stable or unstable Roche-Lobe overflow. These pulsators have great potential in probing detailed physical processes in stellar interiors and mass transfer, as well as in studying the binary star populations.
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