A chemical vapor deposition method is developed for thickness‐controlled (one to four layers), uniform, and continuous films of both defective gallium(II) sulfide (GaS): GaS0.87 and stoichiometric ...GaS. The unique degradation mechanism of GaS0.87 with X‐ray photoelectron spectroscopy and annular dark‐field scanning transmission electron microscopy is studied, and it is found that the poor stability and weak optical signal from GaS are strongly related to photo‐induced oxidation at defects. An enhanced stability of the stoichiometric GaS is demonstrated under laser and strong UV light, and by controlling defects in GaS, the photoresponse range can be changed from vis‐to‐UV to UV‐discriminating. The stoichiometric GaS is suitable for large‐scale, UV‐sensitive, high‐performance photodetector arrays for information encoding under large vis‐light noise, with short response time (<66 ms), excellent UV photoresponsivity (4.7 A W–1 for trilayer GaS), and 26‐times increase of signal‐to‐noise ratio compared with small‐bandgap 2D semiconductors. By comprehensive characterizations from atomic‐scale structures to large‐scale device performances in 2D semiconductors, the study provides insights into the role of defects, the importance of neglected material‐quality control, and how to enhance device performance, and both layer‐controlled defective GaS0.87 and stoichiometric GaS prove to be promising platforms for study of novel phenomena and new applications.
A chemical vapor deposition method is developed for controlling defects in gallium(II) sulfide (GaS), and their influence on the UV photosensing response in devices is elucidated. Defects in GaS act as sites of photoinduced oxidation and degradation. High‐quality GaS 2D films show uniform UV photodetector response and defect tuning enables selective UV sensing.
Long-Term Efficacy of a Hepatitis E Vaccine Zhang, Jun; Zhang, Xue-Feng; Huang, Shou-Jie ...
New England journal of medicine/The New England journal of medicine,
03/2015, Volume:
372, Issue:
10
Journal Article
Peer reviewed
Open access
Hepatitis E virus is a common cause of illness worldwide and is associated with severe complications, especially in pregnant women. In this report, the long-term efficacy, immunogenicity, and safety ...of a hepatitis E vaccine are described.
Hepatitis E virus (HEV) is a common cause of acute hepatitis worldwide.
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HEV infection occurs in two distinct epidemiologic patterns.
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The most common pattern is waterborne infection, which is caused by HEV genotype 1 or 2 and occurs mainly in resource-limited countries, often in large, protracted outbreaks or in sporadic cases associated with high mortality among pregnant women.
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The other pattern is transmission from animals and humans, which is caused by HEV genotype 3 or 4 and occurs widely in both resource-limited and developed countries.
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Rein et al.
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estimated the incidence of hepatitis E in areas . . .
Triangular nanovoids in 2D materials transition metal dichalcogenides have vertex points that cause stress concentration and lead to sharp crack propagation and failure. Here, the atomistic mechanics ...of back folding around triangular nanovoids in monolayer WS2 sheets is examined. Combining atomic‐resolution images from annular dark‐field scanning transmission electron microscopy with reactive molecular modelling, it is revealed that the folding edge formation has statistical preferences under geometric conditions based on the orientation mismatch. It is further investigated how loading directions and strong interlayer friction, interplay with WS2 lattice's crack preference, govern the deformation and fracture pattern around folding edges. These results provide fundamental insights into the combination of fracture and folding in flexible monolayer crystals and the resultant Moiré lattices.
Combining atomic‐resolution images from annular dark‐field scanning transmission electron microscopy with reactive molecular modelling, it is revealed that the folding edge formation has statistical preferences under geometric conditions based on the orientation mismatch. It is further investigated how loading directions and strong interlayer friction, interplay with WS2 lattice's crack preference, govern the deformation and fracture pattern around folding edges.
Existing clinical studies supported the potential efficacy of mesenchymal stromal cells as well as derived exosomes in the treatment of COVID-19. We aimed to explore the safety and efficiency of ...aerosol inhalation of the exosomes derived from human adipose-derived MSCs (haMSC-Exos) in patients with COVID-19.
The MEXCOVID trial is a phase 2a single-arm, open-labelled, interventional trial and patients were enrolled in Jinyintan Hospital, Wuhan, China. Eligible 7 patients were assigned to receive the daily dose of haMSCs-Exos (2.0 × 10
nano vesicles) for consecutively 5 days. The primary outcomes included the incidence of prespecified inhalation-associated events and serious adverse events. We also observed the demographic data, clinical characteristics, laboratory results including lymphocyte count, levels of D-dimer and IL-6 as well as chest imaging.
Seven severe COVID-19 related pneumonia patients (4 males and 3 females) were enrolled and received nebulized haMSC-Exos. The median age was 57 year (interquartile range (IQR), 43 year to 70 year). The median time from onset of symptoms to hospital admission and administration of nebulized haMSC-Exos was 30 days (IQR, 15 days to 40 days) and 54 d (IQR, 34 d to 69 d), respectively. All COVID-19 patients tolerated the haMSC-Exos nebulization well, with no evidence of prespecified adverse events or clinical instability during the nebulization or during the immediate post-nebulization period. All patients presented a slight increase of serum lymphocyte counts (median as 1.61 × 10
/L vs. 1.78 × 10
/L). Different degrees of resolution of pulmonary lesions after aerosol inhalation of haMSC-Exos were observed among all patients, more obviously in 4 of 7 patients.
Our trial shows that a consecutive 5 days inhalation dose of clinical grade haMSC-Exos up to a total amount of 2.0 × 10
nano vesicles was feasible and well tolerated in seven COVID-19 patients, with no evidence of prespecified adverse events, immediate clinical instability, or dose-relevant toxicity at any of the doses tested. This safety profile is seemingly followed by CT imaging improvement within 7 days. Further trials will have to confirm the long-term safety or efficacy in larger population.
MEXCOVID, NCT04276987.
It is shown that tilt grain boundaries (GBs) in bilayer 2D crystals of the transition metal dichalcogenide WS2 can be atomically sharp, where top and bottom layer GBs are located within sub‐nanometer ...distances of each other. This expands the current knowledge of GBs in 2D bilayer crystals, beyond the established large overlapping GB types typically formed in chemical vapor deposition growth, to now include atomically sharp dual bilayer GBs. By using atomic‐resolution annular dark‐field scanning transmission electron microscopy (ADF‐STEM) imaging, different atomic structures in the dual GBs are distinguished considering bilayers with a 3R (AB stacking)/2H (AA′ stacking) interface as well as bilayers with 2H/2H boundaries. An in situ heating holder is used in ADF‐STEM and the GBs are stable to at least 800 °C, with negligible thermally induced reconstructions observed. Normal dislocation cores are seen in one WS2 layer, but the second WS2 layer has different dislocation structures not seen in freestanding monolayers, which have metal‐rich clusters to accommodate the stacking mismatch of the 2H:3R interface. These results reveal the competition between maintaining van der Waals bilayer stacking uniformity and dislocation cores required to stitch tilted bilayer GBs together.
Long‐range atomically sharp dual tilt grain boundaries are found within bilayer WS2 2D layered crystals grown by chemical vapor deposition. In situ heating experiments within the electron microscope show they are stable to at least 800 °C. The dislocation cores needed for these bilayer interfaces are more complex than monolayer grain boundaries due to competing van der Waals interlayer forces.
We show how an oxide passivating layer on the Cu surface before the growth of h-BN by chemical vapor deposition (CVD) can lead to increased domain sizes from 1 to 20 μm by reducing the nucleation ...density from 106 to 103 mm–2. The h-BN domains within each Cu grain are well-oriented, indicating an epitaxial relationship between the h-BN crystals and the Cu growth substrates that leads to larger crystal domains within the film of ∼100 μm. Continuous films are grown and show a high degree of monolayer uniformity. This CVD approach removes the need for low pressures, electrochemical polishing, and expensive substrates for large-area continuous films of h-BN monolayers, which is beneficial for industrial applications that require scalable synthesis.
The solid progress in the study of a single two-dimensional (2D) material underpins the development for creating 2D material assemblies with various electronic and optoelectronic properties. We ...introduce an asymmetric structure by stacking monolayer semiconducting tungsten disulfide, metallic graphene, and insulating boron nitride to fabricate numerous red channel light-emitting devices (LEDs). All the 2D crystals were grown by chemical vapor deposition (CVD), which has great potential for future industrial scale-up. Our LEDs exhibit visibly observable electroluminescence (EL) at both 5.5 V forward and 7.0 V backward biasing, which correlates well with our asymmetric design. The red emission can last for at least several minutes, and the success rate of the working device that can emit detectable EL is up to 80%. In addition, we show that sample degradation is prone to happen when a continuing bias, much higher than the threshold voltage, is applied. Our success of using high-quality CVD-grown 2D materials for red light emitters is expected to provide the basis for flexible and transparent displays.
We show that reducing the degree of van der Waals overlapping in all 2D ultrathin lateral devices composed of graphene:WS2:graphene leads to significant increase in photodetector responsivity. This ...is achieved by directly growing WS2 using chemical vapor deposition (CVD) in prepatterned graphene gaps to create epitaxial interfaces. Direct-CVD-grown graphene:WS2:graphene lateral photodetecting transistors exhibit high photoresponsivities reaching 121 A/W under 2.7 × 105 mW/cm2 532 nm illumination, which is around 2 orders of magnitude higher than similar devices made by the layer-by-layer transfer method. The photoresponsivity of our direct-CVD-grown device shows negative correlation with illumination power under different gate voltages, which is different from similar devices made by the transfer method. We show that the high photoresponsivity is due to the lowering of effective Schottky barrier height by improving the contact between graphene and WS2. Furthermore, the direct CVD growth reduces overlapping sections of WS2:Gr and leads to more uniform lateral systems. This approach provides insights into scalable manufacturing of high-quality 2D lateral electronic and optoelectronic devices.
We here describe a new, selective indium-promoted silver-mediated intermolecular oxidative 1,4-alkylarylation of 1,3-dienes with α-carbonyl alkyl bromides and N-heterocycles for producing ...functionalized N-heterocycles, which is characterized by its exquisitely controllable regio-/stereo-selectivity and excellent tolerance of functional groups. Mechanistically, the formation of the carbonyl-coordinated η
3
-allyl-In complex radical intermediate is the key factor for successfully achieving regio- and stereo-selectivity toward 1,4-difunctionalization and (
E
)-isomers.
A selective indium-promoted silver-mediated intermolecular oxidative 1,4-alkylarylation of 1,3-dienes with α-carbonyl alkyl bromides and N-heterocycles was reported.
The geochemical fractions of trace metals in the coastal sediments of the central western Taiwan were examined, employing the Tessier sequential extraction method, and the metals contamination status ...of the analyzed sediments were also evaluated in the present study. Based on the metal fraction present in sediments, trace metals can be divided into three groups: (1) Al, Cr, Fe, Ni and Zn; (2) Cu and Pb and (3) Mn. In group (1) metal, the metals’ total concentrations were chiefly dominated by the residual fraction, exceeding 80% of the total concentration pool. In group (2) metal, the metals’ total concentrations were dominated by three labile fractions, carbonate, Fe-Mn oxides and organic, accounting for nearly 65% of the total pool, and the residual fraction contributed 35% of the total concentrations. Over 90% of Mn total concentrations were shared by three fractions, carbonate, Fe-Mn oxides and the residual fraction. The statistic results indicated that the total organic carbon contents in sediments played a more important role in influencing the metals contents in sediments. The contamination assessment results suggested that the Mailiao coastal sediments were minorly contaminated by trace metals. Lead should be paid more concerns because Pb total concentrations at some sediments exceeded the value (46.7 mg/kg) of effect range low, USA, and Pb was mainly present in the labile fraction.
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