Greatly Enhanced Methanol Oxidation Reaction of CoPt Truncated Octahedral Nanoparticles by External Magnetic Fields

Tunable behavior in electrocatalysis by external multifields,such as magnetic field,thermal field,and electric field,is the most promising strategy to expand the theory,design,and synthesis of state-of-the-art catalysts and the cell in the near future.Here,a systematic investigation for the effect of external magnetic field and thermal field on methanol oxidation reactions(MOR)in magnetic nanoparticles is reported.For Co_(42)Pt_(58)truncated octahedral nanoparticles(TONPs),the catalytic performance in MOR is greatly increased to the maximum of 14.1%by applying a magnetic field up to 3000 Oe,and it shows a monotonical increase with increasing working temperature.The magnetic enhanced effect is closely related to the Co content of Co_(x)Pt_(100-x)TONPs.Furthermore,the enhancement effect under a magnetic field is more obvious for Co_(42)Pt_(58)TONPs annealed at 650℃.First-principle calculation points out that the magnetic fields can facilitate the dehydrogenation of both methanol and water by suppression of entropy of the electron spin and lowering of the activation barrier,where OH_(ad)intermediates on Co sites play a more important role.The application of magnetic fields together with thermal fields in MOR provides a new prospect to manipulate the performance of direct methanol fuel cells,which will accelerate their potential applications.

Epidemiologic Features, Radiological Findings and Clinical Outcomes of 19 Patients with COVID-19 in a Single Center in Beijing, China

Objective To describe the epidemiologic,clinical,laboratory,and radiological characteristics and prognoses of COVID-19 confirmed patients in a single center in Beijing,China.Methods The study retrospectively included 19 patients with nucleic acid-confirmed SARS-CoV^2 infection at our hospital from January 20 to March 5,2020.The final follow-up date was March 14,2020.The epidemiologic and clinical information was obtained through direct communication with the patients or their family members.Laboratory results retrieved from medical records and radiological images were analyzed both qualitatively by two senior chest radiologists as well as quantitatively via an artificial intelligence software.Results We identified 5 family clusters(13/19,68.4%)from the study cohort.All cases had good clinical prognoses and were either mild(3/19)or moderate(16/19)clinical types.Fever(15/19,78.9%)and dry cough(11/19,57.9%)were common symptoms,Two patients received negative results for more than three consecutive viral nucleic acid tests.The longest interval between an initial CT abnormal finding and a confirmed diagnosis was 30 days.One patient's nucleic acid test turned positive on the follow-up examination after discharge.The presence of radiological abnormalities was non-specific for the diagnosis of COVID-19.Conclusions COVID-19 patients with mild or no clinical symptoms are common in Beijing,China.Radiological abnormalities are mostly non-specific and massive CT examinations for COVID-19 screening should be avoided.Analyses of the contact histories of diagnosed cases in combination with clinical,radiological and laboratory findings are crucial for the early detection of COVID-19.Close monitoring after discharge is also recommended.

Magnetoresistance anomaly in Fe_(5)GeTe_(2)homo-junctions induced by its intrinsic transition

Two-dimensional van der Waals(2D vdW)magnets have attracted great attention recently and possess the unprecedented advantages of incorporating high-quality vdW heterostructures and homostructures into spintronic devices,and exploring various physical phenomena or technologies.Among them,Fe_(5)GeTe_(2)(F5GT)has ferromagnetic order close to room temperature,however the magnetic properties near its intrinsic transitions and F5GT-based 2D devices remain mostly unexplored.Here,we systematically demonstrate the peculiar magnetic properties of Fe_(5)GeTe_(2)nanoflakes near its intrinsic transition temperature(Tp)which is far lower than its Curie temperature(TC)of~265 K,and firstly discover anomalous magnetoresistance effect in F5GT homo-junctions by magneto-transport measurements.The strongest anomalous Hall effect occurs around Tp which is located in a temperature range from 130 to 160 K for the F5GT nanoflakes with different thicknesses.Furthermore,negative magnetoresistance(N-MR)and butterfly-shaped magnetoresistance(B-MR)are observed in F5GT homo-junction devices,and they appeared only in an intermediate temperature range from 110 to 160 K,noticeably showing the maxima near the T_(p)rather than the lowest temperature.Our experimental results clearly reveal the significant influence of intrinsic transitions on magnetic properties of F5GT and magnetoresistance effect in F5GT homo-junction devices,which imply a new strategy to achieve highperformance 2D spintronic devices by tuning intrinsic magnetic or structural transitions in 2D vdW magnets.

新型冠状病毒肺炎疫情对放射科住院医师规范化培训的影响及思考

我国放射科住院医师规范化培训发展迅速,在新型冠状病毒肺炎疫情防控期间,大量教学内容转化为线上教育,面临线上教学条件和资源不足,在线课程互动不足等挑战,为此,我们需要加强线上课程资源建设,增加线上课程的互动交流,优化医学影像学人才的培养体系。

Fast two-dimensional weighted least squares techniques for the design of two-dimensional finite impulse response filters

This paper focuses on the design of two-dimensional （2D） quadrantally symmetric finite impulse response （FIR） filters, and presents three very efficient algorithms for the weighted least squares （WLS） design with a weight matrix that assigns four different weights to four different frequency bands. The first algorithm seeks for iterative solutions to the matrix equation describing the optimality condition of the design problem. The second algorithm aims at the limit solution of the solution sequence to the first algorithm, analytically obtained by using matrix diagonalization techniques. The third algorithm belongs to the category of iterative reweighting techniques. It uses the second algorithm as its iteration core, and aims at reducing the maximum magnitude error of the filter by iteratively adjusting the four entry values of the weight matrix. Design examples are provided to demonstrate the performance of the proposed algorithms.