Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero energy end states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is the etiological agent responsible for the global COVID-19 (coronavirus disease 2019) outbreak. The main protease of SARS-CoV-2, Mpro, is a key enzyme that plays a pivotal role in mediating viral replication and transcription. We designed and synthesized two lead compounds (11a and 11b) targeting Mpro. Both exhibited excellent inhibitory activity and potent anti–SARS-CoV-2 infection activity. The x-ray crystal structures of SARS-CoV-2 Mpro in complex with 11a or 11b, both determined at a resolution of 1.5 angstroms, showed that the aldehyde groups of 11a and 11b are covalently bound to cysteine 145 of Mpro. Both compounds showed good pharmacokinetic properties in vivo, and 11a also exhibited low toxicity, which suggests that these compounds are promising drug candidates.

Review of some recent work ]A multi-input multi-output (MIMO) radar system, unlike standard phased-array radar, can transmit, via its antennas, multiple probing signals that may be correlated or uncorrelated with each other. While the companion article by Blum et al., to appear in the November issue, exploited the diversity offered by widely separated transmit/receive antenna elements, we focus on the merits of the waveform diversity allowed by transmit and receive antenna arrays containing elements that are colocated. For the latter type of MIMO radar systems, we provide an overview of recent results showing that the waveform diversity enables the MIMO radar superiority in several fundamental aspects, including: 1) significantly improved parameter identifiability, 2) direct applicability of adaptive arrays for target detection and parameter estimation, and 3) much enhanced flexibility for transmit beampattern design. Specifically, we show that 1) the maximum number of targets that can be uniquely identified by the MIMO radar is up to M t times that of its phased-array counterpart, where M t is the number of transmit antennas, 2) the echoes due to targets at different locations can be linearly independent of each other, which allows the [ Jian Li and Petre Stoica ] MIMO Radar with Colocated AntennasDigital Object Identifier 10. 1109 /MSP.2007 direct application of many adaptive techniques to achieve high resolution and excellent interference rejection capability, and 3) the probing signals transmitted via its antennas can be optimized to obtain several transmit beampattern designs with superior performance. For example, the covariance matrix of the probing signal vector transmitted by the MIMO radar can be optimized to maximize the power around the locations of the targets of interest and also to minimize the cross-correlation of the signals reflected back to the radar by these targets, thereby significantly improving the performance of adaptive MIMO radar techniques. Additionally, we demonstrate the advantages of several MIMO transmit beampattern designs, including a beampattern matching design and a minimum sidelobe beampattern design, over their phased-array counterparts. In conclusion, the two articles in this issue show that MIMO radar is a fertile research ground that merits further investigation, including reaping the full benefits of both types of diversity covered in the two articles.

With increasing clinical emergence of multidrug-resistant Gram-negative pathogens and the paucity of new agents to combat these infections, colistin (administered as its inactive prodrug colistin methanesulfonate [CMS]) has reemerged as a treatment option, especially for critically ill patients. There has been a dearth of pharmacokinetic (PK) data available to guide dosing in critically ill patients, including those on renal replacement therapy. In an ongoing study to develop a population PK model for CMS and colistin, 105 patients have been studied to date; these included 12 patients on hemodialysis and 4 on continuous renal replacement therapy. For patients not on renal replacement, there was a wide variance in creatinine clearance, ranging from 3 to 169 ml/min/1.73 m 2 . Each patient was treated with a physicianselected CMS dosage regimen, and 8 blood samples for PK analysis were collected across a dosage interval on day 3 or 4 of therapy. A linear PK model with two compartments for CMS and one compartment for formed colistin best described the data. Covariates included creatinine clearance on the total clearance of CMS and colistin, as well as body weight on the central volume of CMS. Model-fitted parameter estimates were used to derive suggested loading and maintenance dosing regimens for various categories of patients, including those on hemodialysis and continuous renal replacement. Based on our current understanding of colistin PK and pharmacodynamic relationships, colistin may best be used as part of a highly active combination, especially for patients with moderate to good renal function and/or for organisms with MICs of >1.0 mg/liter.

Rationale: The coronavirus disease (COVID-19) pandemic is now a global health concern. Objectives: We compared the clinical characteristics, laboratory examinations, computed tomography images, and treatments of patients with COVID-19 from three different cities in China. Methods: A total of 476 patients were recruited from January 1, 2020, to February 15, 2020, at three hospitals in Wuhan, Shanghai, and Anhui. The patients were divided into four groups according to age and into three groups (moderate, severe, and critical) according to the fifth edition of the Guidelines on the Diagnosis and Treatment of COVID-19 issued by the National Health Commission of China. Measurements and Main Results: The incidence of comorbidities was higher in the severe (46.3%) and critical (67.1%) groups than in the moderate group (37.8%). More patients were taking angiotensinconverting enzyme inhibitors/angiotensin II receptor blockers in the moderate group than in the severe and critical groups. More patients had multiple lung lobe involvement and pleural effusion in the critical group than in the moderate group. More patients received antiviral agents within the first 4 days in the moderate group than in the severe group, and more patients received antibiotics and corticosteroids in the critical and severe groups. Patients .75 years old had a significantly lower survival rate than younger patients. Conclusions: Multiple organ dysfunction and impaired immune function were the typical characteristics of patients with severe or critical illness. There was a significant difference in the use of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers among patients with different severities of disease. Involvement of multiple lung lobes and pleural effusion were associated with the severity of COVID-19. Advanced age (>75 yr) was a risk factor for mortality.

Although considerable progress has been made in direct synthesis gas (syngas) conversion to light olefins (C2(=)-C4(=)) via Fischer-Tropsch synthesis (FTS), the wide product distribution remains a challenge, with a theoretical limit of only 58% for C2-C4 hydrocarbons. We present a process that reaches C2(=)-C4(=) selectivity as high as 80% and C2-C4 94% at carbon monoxide (CO) conversion of 17%. This is enabled by a bifunctional catalyst affording two types of active sites with complementary properties. The partially reduced oxide surface (ZnCrO(x)) activates CO and H2, and C-C coupling is subsequently manipulated within the confined acidic pores of zeolites. No obvious deactivation is observed within 110 hours. Furthermore, this composite catalyst and the process may allow use of coal- and biomass-derived syngas with a low H2/CO ratio.

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We performed a genome-wide association study (GWAS) of systemic lupus erythematosus (SLE) in a Chinese Han population by genotyping 1,047 cases and 1,205 controls using Illumina Human610-Quad BeadChips and replicating 78 SNPs in two additional cohorts (3,152 cases and 7,050 controls). We identified nine new susceptibility loci (ETS1, IKZF1, RASGRP3, SLC15A4, TNIP1, 7q11.23, 10q11.22, 11q23.3 and 16p11.2; 1.77 x 10(-25) < or = P(combined) < or = 2.77 x 10(-8)) and confirmed seven previously reported loci (BLK, IRF5, STAT4, TNFAIP3, TNFSF4, 6q21 and 22q11.21; 5.17 x 10(-42) < or = P(combined) < or = 5.18 x 10(-12)). Comparison with previous GWAS findings highlighted the genetic heterogeneity of SLE susceptibility between Chinese Han and European populations. This study not only advances our understanding of the genetic basis of SLE but also highlights the value of performing GWAS in diverse ancestral populations.