Numerical simulation of packed-bed reactor for oxidative coupling of methane

A three-dimensional geometric model of the oxidative coupling of methane （OCM） packed-bed reactor loaded with Na2WO4-Mn/SiO2 partic- ulate catalyst was set up, and an improved Stansch kinetic model was established to calculate the OCM reactions using the computational fluid dynamics method and Fluent software. The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant was 80 mL/min under standard state, the ratio of CH4/O2 was 3, the temperature and pressure were 800 ℃ and 1 atm, respectively. The contour of the characteristics parameters in the catalyst bed was analyzed, such as the species mass fractions, temperature, the heat flux on side wall surface, pressure, fluid density and velocity. The results showed that the calculated values matched well with the experimental values on the conversion of CH4 and the selectivity to products （C2H6, C2H4, CO2, CO） in the reactor outlet with an error range of 4-2%. The mass fractions of CH4 and O2 decreased from 0.6 and 0.4 in the catalyst bed inlet to 0.436 and 0.142 in the outlet, where the mass fractions of C2H6, C2H4, CO and CO2 were 0.035, 0.061, 0.032 and 0.106, respectively. Due to the existence of laminar boundary layer, the contours of each component bent upwards in the vicinity of the boundary layer. This OCM reaction was volume increase reaction and the total moles of products were greater than those of reactants. The flow field in the catalyst bed maintained constant temperature and pressure. The fluid density decreased gradually from 2.28 kg/m3 in the inlet of the catalyst bed to 2.22 kg/m3 in the outlet of the catalyst bed, while the velocity increased from 0.108 m/s to 0.115 m/s.

Fast and accurate machine learning prediction of phonon scattering rates and lattice thermal conductivity

Lattice thermal conductivity is important for many applications,but experimental measurements or first principles calculations including three-phonon and four-phonon scattering are expensive or even unaffordable.Machine learning approaches that can achieve similar accuracy have been a long-standing open question.Despite recent progress,machine learning models using structural information as descriptors fall short of experimental or first principles accuracy.This study presents a machine learning approach that predicts phonon scattering rates and thermal conductivity with experimental and first principles accuracy.The success of our approach is enabled by mitigating computational challenges associated with the high skewness of phonon scattering rates and their complex contributions to the total thermal resistance.Transfer learning between different orders of phonon scattering can further improve the model performance.Our surrogates offer up to two orders of magnitude acceleration compared to first principles calculations and would enable large-scale thermal transport informatics.

Emerging Metal Single-Atom Materials:From Fundamentals to Energy Applications

CONSPECTUS:With the development of nanotechnology and characterization techniques,it has been realized that the reactivity of metal nanoparticles mainly depends on some unsaturated coordination atoms on the surface.However,only a small fraction of the surface exposed atoms can access the reactants and act as reactive sites,resulting in low utilization of metal atoms.Moreover,due to the complex structure of metal nanoparticles,the metal atoms exposed on the surface are likely to be in different chemical environments and may act as multiple active centers to catalyze the reactants,which brings great difficulties in the establishment of the structure−activity relationship of metal nanoparticles.

Erratum to“Impact of satellite blood culture on early diagnosis of sepsis”[Journal of Intensive Medicine volume 2(2022)56–60]

The publisher regrets the article titled“Impact of satellite blood culture on early diagnosis of sepsis,”[1]published on pages 56-60,Issue 1,Volume 2 in Journal of Intensive Medicine(https://www.sciencedirect.com/science/article/pii/S2667100X21000475)contains a mistake in Abstract.The sentence in the Results“median ICU lengths of stay were 18.00 days and 23.50 days”should be“median lengths of hospital stays were 18.00 days and 23.50 days”.The publisher would like to apologize for any inconvenience caused.

Structural optimization of acceptor molecules guided by a semi-empirical model for organic solar cells with efficiency over 15%

Despite much progress in organic solar cells(OSCs),higher efficiency is still the most desirable goal and can indeed be obtained through rational design of active layer materials and device optimization according to the theoretical prediction.Herein,under the guidance of a semi-empirical model,two new non-fullerene small molecule acceptors(NFSMAs)with an acceptor-donor-acceptor(A-D-A)architecture,namely,6 T-OFIC and 5 T-OFIC,have been designed and synthesized.6 T-OFIC exhibits wider absorption spectrum and a red-shifted absorption onset(λ_(onset))of 946 nm due to its extended conjugation central unit.In contrast,5 T-OFIC with five-thiophene-fused backbone has an absorption with theλ_(onset)of 927 nm,which is closer to the predicted absorption range for the best single junction cells based on the semiempirical model.Consequently,the device based on 5 T-OFIC yields a higher power conversion efficiency(PCE)of 13.43%compared with 12.35%of the 6 T-OFIC-based device.Furthermore,an impressive PCE of 15.45%was achieved for the5 T-OFIC-based device when using F-2 Cl as the third component.5 T-OFIC offers one of a few acceptor cases with efficiencies over 15%other than Y6 derivatives.

Improving current and mitigating energy loss in ternary organic photovoltaics enabled by two well-compatible small molecule acceptors

Ternary organic photovoltaic(OPV)strategy is an effective but facile approach to enhance the photovoltaic performance for single-junction devices.Herein,a series of ternary OPVs were fabricated by employing a wide bandgap donor(PBDB-TF)and two acceptor-donor-acceptor(A-D-A)-type nonfullerene small molecule acceptors(NF-SMAs,called F-2 Cl and 3 TT-OCIC).As the third component,the near-infrared SMA,3 TT-OCIC,has complementary absorption spectrum,narrow bandgap and wellcompatible crystallization property to the host acceptor(F-2 Cl)for efficient ternary OPVs.With these,the optimal ternary devices yield significantly enhanced power conversion efficiency of 15.23%,one of the very few examples with PCE higher than15%other than Y6 systems.This is mainly attributed to the increased short-circuit current density of 24.92 m A cm^(-2) and dramatically decreased energy loss of 0.53 e V.This work presents a successful example for simultaneously improving current,minimizing energy loss and together with modifying the morphology of active layers in OPVs,which will contribute to the further construction of high performance ternary OPVs.

Impact of satellite blood culture on early diagnosis of sepsis

Background:The aim of this study was to assess whether satellite blood culture(SBC)can improve turnaround times,antibiotic switching,and patient prognosis,relative to laboratory blood culture(LBC).Methods:Patients with sepsis treated in the intensive care units(ICUs)of Henan Provincial People’s Hospital from February 5,2018 to January 19,2019 who met the inclusion criteria were recruited to the study and divided into the SBC group and LBC group according to different blood culture methods.Patient demographics,blood culture,antibiotic adjustment,and prognosis data were collected and compared between the two groups.Results:A total of 204 blood culture sets from 52 ICU patients,including 100 from the medical microbiology LBC group and 104 from the SBC group,were analyzed in this study.There was no significant difference in the positive rates between the two groups.Time from specimen collection to incubation was significantly shorter in the SBC group than that in the LBC group(1.65 h vs.3.51 h,z=−4.09,P<0.001).The median time from specimen collection to notification of blood culture positivity was 24.83 h in the SBC group and 27.83 h in the LBC group.Median times from adjustment of antibiotics according to the first report were 26.05 h and 51.71 h in the SBC and LBC groups,respectively,while those according to the final report were 97.17 h and 111.45 h,respectively.Median ICU lengths of stay were 15.00 days and 17.00 days in the SBC and LBC groups,respectively,and median ICU lengths of stay were 18.00 days and 23.50 days,respectively.Mean hospitalization costs were 157.99 and 186.73 thousand yuan in the SBC and LBC groups,respectively.Conclusion:SBC can significantly reduce blood culture turnaround times;however,there were no significant differences between the two blood culture methods in initial reporting of positive cultures,time to adjustment of antibiotic therapy,or medical costs,despite a trend toward improvement.