A review on heterogeneous solid catalysts and related catalytic mechanisms for epoxidation of olefins with H2O2

The epoxidation reaction using heterogeneous solid catalysts with H2O2 as oxidants are environmentally friendly routes to produce extensively useful epoxides which are traditionally obtained from capital-intensive or environmentally polluted processes. In this paper, various types of solid catalysts for the epoxidation of olefins with H2O2 as oxidants are reviewed. The efficient catalysts reported include microporous and mesoporous molecular sieves, layered-type materials, inorganic oxides, supported catalysts, zeolite encapsulated metal complexes, polyoxometalates, and supported organometallic catalysts. The proposed reaction mechanisms over different solid catalysts are summarized. The problems and perspectives to further efficiently improve the catalytic performances of the concerned heterogeneous catalysts for epoxidation reaction are remarked

PSR J1926-0652: A Pulsar with Interesting Emission Properties Discovered at FAST

We describe PSR J1926-0652, a pulsar recently discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using sensitive single-pulse detections from FAST and long-term timing observations from the Parkes 64-m radio telescope, we probed phenomena on both long and short time scales. The FAST observations covered a wide frequency range from 270 to 800 MHz, enabling individual pulses to be studied in detail. The pulsar exhibits at least four profile components, short-term nulling lasting from 4 to 450 pulses, complex subpulse drifting behaviours and intermittency on scales of tens of minutes. While the average band spacing P3 is relatively constant across different bursts and components, significant variations in the separation of adjacent bands are seen, especially near the beginning and end of a burst. Band shapes and slopes are quite variable, especially for the trailing components and for the shorter bursts. We show that for each burst the last detectable pulse prior to emission ceasing has different properties compared to other pulses. These complexities pose challenges for the classic carousel-type models.Comment: 13pages with 12 figure

Efficacy of non-invasive brain stimulation for disorders of consciousness: a systematic review and meta-analysis

ObjectiveThe aim of this study is to evaluate the efficacy of non-invasive brain stimulation (NIBS) in patients with disorders of consciousness (DoC) and compare differences in efficacy between different stimulation modalities.MethodsWe searched the PubMed, Cochrane Library, Web of Science, and EMBASE databases for all studies published in English from inception to April 2023. Literature screening and quality assessment were performed independently by two investigators. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to evaluate the therapeutic effects of NIBS. The Cochrane Q test and I2 statistic were used to evaluate heterogeneity between studies. Subgroup analysis was performed to identify the source of heterogeneity, and differences in efficacy between different stimulation modalities were compared by Bayesian analysis.ResultsA total of 17 studies with 377 DoC patients were included. NIBS significantly improved the state of consciousness in DoC patients when compared to sham stimulation (WMD: 0.81; 95% CI: 0.46, 1.17; I2 = 78.2%, p = 0.000). When divided into subgroups according to stimulation modalities, the heterogeneity of each subgroup was significantly lower than before (I2: 0.00–30.4%, p >0.05); different stimulation modalities may be the main source of such heterogeneity. Bayesian analysis, based on different stimulation modalities, indicated that a patient’s state of consciousness improved most significantly after repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (DLPFC). Diagnosis-based subgroup analysis showed that NIBS significantly improved the state of consciousness in patients with a minimal consciousness state (WMD: 1.11; 95% CI: 0.37, 1.86) but not in patients with unresponsive wakefulness syndrome or a vegetative state (WMD: 0.31; 95% CI: −0.09, 0.71). Subgroup analysis based on observation time showed that single treatment did not improve the state of consciousness in DoC patients (WMD: 0.28; 95% CI: −0.27, 0.82) while multiple treatments could (WMD: 1.05; 95% CI: 0.49, 1.61). Furthermore, NIBS had long-term effects on DoC patients (WMD: 0.79; 95% CI: 0.08–1.49).ConclusionAvailable evidence suggests that the use of NIBS on patients with DoC is more effective than sham stimulation, and that rTMS of the left DLPFC may be the most prominent stimulation modality

Joint Optimization of a Rail Transit Route and Bus Routes in a Transit Corridor

Urban transit network is mainly composed of rail transit routes and bus routes in many large cities of China. Previous studies have been made to optimal either rail transit network design or bus network design. This paper was concerned with joint optimization of a rail transit route and bus routes in a transit corridor. Firstly, a method for classifying bus routes under a given rail route transit was proposed. Then, a multi-objective model was developed for designing an integrated rail transit and bus network to maximize rail ridership and minimize total passenger travel time. An algorithm for solving the proposed model based on genetic algorithm was presented. At last, a numerical example was given. The results demonstrate feasible and effective of the proposed model and solution methodology, and show that rail ridership increases and total passenger travel time declines after optimization

A Modified Cellular Automaton Approach for Mixed Bicycle Traffic Flow Modeling

Several previous studies have used the Cellular Automaton (CA) for the modeling of bicycle traffic flow. However, previous CA models have several limitations, resulting in differences between the simulated and the observed traffic flow features. The primary objective of this study is to propose a modified CA model for simulating the characteristics of mixed bicycle traffic flow. Field data were collected on physically separated bicycle path in Shanghai, China, and were used to calibrate the CA model using the genetic algorithm. Traffic flow features between simulations of several CA models and field observations were compared. The results showed that our modified CA model produced more accurate simulation for the fundamental diagram and the passing events in mixed bicycle traffic flow. Based on our model, the bicycle traffic flow features, including the fundamental diagram, the number of passing events, and the number of lane changes, were analyzed. We also analyzed the traffic flow features with different traffic densities, traffic components on different travel lanes. Results of the study can provide important information for understanding and simulating the operations of mixed bicycle traffic flow

Ternary Cobalt-Copper-Niobium Catalysts for the Selective CO Hydrogenation to Higher Alcohols

Novel "CoCuNb" ternary catalysts with bimodal nanosized particle structure, in the absence of a generic support material, were designed and successfully tested in higher alcohol production via CO hydrogenation. The selectivities to primary alcohols with an optimized C2-C5 slate usually exceeded the 50 wt % level, and the combined selectivities to 1-alcohols/1-alkenes reached up to ∼73 wt % for CO conversions ranging between ∼5% and nearly 20%. The bimodal nanosized particle distribution, achieved through oxalate coprecipitation, contained Co-Cu particles with sizes ranging from 25 to 40 nm. Smaller particles between 4 and 8 nm were identified as Nb oxides and played the role of a structural dispersant ("spacer") and promoter of 1-alcohol/1-olefin production. X-ray photoelectron spectroscopy revealed NbOx to contain major amounts of species with Nb in the 4+ oxidation state. (Graph Presented).SCOPUS: ar.jinfo:eu-repo/semantics/publishe