RESUMO
To elucidate the seroprevalence and rate of asymptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Japanese children, serological analysis was performed using serum samples collected from March 2020 to February 2023. A total of 1493 serum samples were collected during the first study period (March 2020 to February 2021). None of the serum samples was positive for SARS-CoV-2 antibody. In the second period (March 2021 to February 2022), seven of the 1055 patients (0.7%) experienced SARS-CoV-2 infection. The third period (March 2022 to February 2023) was divided into three terms: from March to June 30, 2022; from July to October 2022; and from November 2022 to February 2023. The seroprevalence gradually increased throughout this period, with rates of 6.0%, 18.6%, and 30.4% in the three terms, respectively. Pediatric cases of asymptomatic SARS-CoV-2 infection occurred after the surge of Omicron variants. Since none of the SARS-CoV-2 antibody-positive patients had a previous history of coronavirus disease 2019, the seroprevalence rate in this study may represent the rate of asymptomatic infection.
Assuntos
Anticorpos Antivirais , Infecções Assintomáticas , COVID-19 , SARS-CoV-2 , Humanos , COVID-19/epidemiologia , COVID-19/diagnóstico , Estudos Soroepidemiológicos , Criança , Japão/epidemiologia , Feminino , Pré-Escolar , Masculino , Infecções Assintomáticas/epidemiologia , SARS-CoV-2/imunologia , Anticorpos Antivirais/sangue , Lactente , AdolescenteRESUMO
Have you ever imagined reactions of alkenes with hydrogen that result in anything other than hydrogenation or hydrogenative C-C coupling? We have long sought to develop not only hydrogenation catalysts that activate H2 as hydride ions but also electron transfer catalysts that activate H2 as a direct electron donor. Here, we report the reductive cyclopropanation of alkenes using an iridium electron storage catalyst with H2 as the electron source without releasing metal waste from the reductant. We discuss the catalytic mechanism with selectivity to give the trans-isomer. These findings are based on the isolation of three complexes and density functional theory calculations.
RESUMO
We present an Ir complex that extracts electrons from H2 at room temperature and stores them as a H2-derived energy carrier (H2EC) at room temperature. Furthermore, we demonstrate that this complex reduces CO2 to a metal-CO22- species at room temperature, and present the first electrospray ionisation mass spectrum for this compound.
RESUMO
Multisystem inflammatory syndrome in children (MIS-C) was reported as a severe complication of coronavirus disease 2019; an infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and was suggested to be associated with Kawasaki disease (KD) in terms of severe systemic inflammation and mucocutaneous symptoms. Because severe gastrointestinal symptoms and systemic shock are more frequently observed with MIS-C, patients with mild MIS-C might have been diagnosed with KD. In this study, titers of IgG antibodies against the SARS-CoV-2 S (S-IgG) and N proteins (N-IgG) were measured in 99 serum samples collected from patients with KD treated between January 2020 and December 2021 to evaluate the relationship between KD and SARS-CoV-2 infection. S-IgG were detected in only one patient out of 99 patients. This patient had coronavirus disease 2019 (COVID-19) 10 months before KD onset, and was unlikely MIS-C. According to characters of S-IgG and N-IgG, the patients was unlikely infected with SARS-CoV-2 just before the onset of KD. In addition to this study, the 26th Nationwide Survey and previous studies showed an association between KD and SARS-CoV-2 to be unlikely. In conclusion, SARS-CoV-2 infection was not observed in patients with KD until Delta predominance in Japan by the method of detecting SARS-CoV-2 IgG.
Assuntos
COVID-19 , Síndrome de Linfonodos Mucocutâneos , Criança , Humanos , COVID-19/complicações , COVID-19/diagnóstico , SARS-CoV-2 , Síndrome de Linfonodos Mucocutâneos/complicações , Síndrome de Linfonodos Mucocutâneos/diagnóstico , Anticorpos Antivirais , Imunoglobulina GRESUMO
Chemists have long sought to regulate the reactivity of H2 , to yield hydride ions, hydrogen atoms, or electrons on demand. One source of inspiration for achieving this control is [NiFe]hydrogenase ([NiFe]H2 ase), which reacts with H2 to form various hydrogen active species such as NiIII hydride species, NiII hydride species, and NiI low-valent species. Chemists have attempted to synthesize these hydrogen active species not only as models for the active species of [NiFe]H2 ase, but also as electron transfer catalysts. However, the synthesis of NiI complex directly from H2 has not been reported. This paper reports the first example of a single-step synthesis of a NiI complex, via reaction of a NiII complex with H2 , stable for over 3â months at room temperature and we further demonstrate a reductive coupling of acridinium ions as part of a reaction cycle.
RESUMO
A series of (E)-1,2-diaryldigermenes, (Eind)ArGeîGeAr(Eind) [Ar = phenyl (2), thiophen-2-yl (3), 9,9-dimethyl-2-fluorenyl (4) and 2,2'-bithiophen-5-yl (5)], supported by the fused-ring bulky 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl (Eind) groups, have been obtained as yellow-orange to red crystalline solids by the reaction of 1,2-dibromodigermene, (Eind)BrGeîGeBr(Eind) (1), with ArLi. In the crystals of 2-5, the digermene cores show a flexible nature adopting a trans-bent geometry with the trans-bent angles (θ) between the Ge-Ge vector and the CEind-Ge-CAr plane of 34.04(12)° (2), 38.3(3)° and 38.8(3)° (3), 33.69(12)° (4) and 39.30(13)° (5). In the UV-vis spectra, strong π-π* absorptions have been observed with an absorption maximum at 451 nm (ε = 1.3 × 104) (2), 455 nm (ε = 9.7 × 103) (3), 480 nm (ε = 1.3 × 104) (4) and 497 nm (ε = 1.4 × 104) (5), retaining the GeîGe double bond in solution. The absorption data and DFT calculations provide evidence for the intrinsic π-conjugation between the GeîGe chromophore and aromatic rings involving the narrowing of the HOMO-LUMO gaps (ΔE) with the extension of the carbon π-electron systems.
Assuntos
Gastroenterite , Infecções por Rotavirus , Rotavirus , Humanos , Lactente , Imunidade Humoral , Fezes , Doença AgudaRESUMO
The crystalline-state photochromism of a new organorhodium dinuclear complex having n-methoxypropyltetramethylcyclopentadienyl (η5-C5Me4n-C3H6OCH3) and photoresponsive dithionite (µ-O2SSO2) ligands was investigated directly by performing single-crystal X-ray diffraction experiments; a reversible conformational change of the n-methoxypropyl moiety was intriguingly observed during the course of a thermal back-reaction.
RESUMO
This paper reports the first example of C-H arylation of benzene under mild conditions, using H2 as an electron source {turnover numbers (TONs)=0.7-2.0 for 24â h}. The reaction depends on a Rh-based electron storage catalyst, and proceeds at room temperature and in aqueous solution. Furthermore, the H2 is inactive during the radical transfer step, greatly reducing unwanted side reactions.
RESUMO
This paper reports the first example of a reductive C(sp3)-C(sp3) homo-coupling of benzyl/allyl halides in aqueous solution by using H2 as an electron source {turnover numbers (TONs) = 0.5-2.3 for 12 h}. This homo-coupling reaction, promoted by visible light, is catalysed by a water-soluble electron storage catalyst (ESC). The reaction mechanism, and four requirements to make it possible, are also described.
RESUMO
Crystalline-state photochromism of a rhodium dithionite complex with n-propyl moieties was studied directly by performing single crystal X-ray diffraction experiments; a non-linear relationship between the degree of the conformational change of the n-propyl moiety and the degree of the photochromic reaction of the dithionite group (µ-O2SSO2) was observed at -173 °C.
RESUMO
1,2-Dihalodigermenes, (E)-(Eind)XGe[double bond, length as m-dash]GeX(Eind) (X = Br and Cl), bearing the fused-ring bulky Eind group (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl) have been isolated as orange-yellow crystals by the ligand redistribution reaction between the diarylgermylene, (Eind)2Ge:, and GeX2·dioxane in toluene via the cleavage and recombination of the Ge-C and Ge-X bonds. The dihalodigermenes have a Ge[double bond, length as m-dash]Ge double bond character in the crystalline state, but dissociate into halogermylenes, (Eind)XGe:, in solution. The addition of excess LiBr to the THF solution of the bromogermylene, (Eind)BrGe:, led to the formation of an equilibrium mixture containing the lithium bromogermylenoid, [Li+][(Eind)GeBr2]-. The bromogermylenoid can be isolated as a cryptand-separated potassium ion pair, [K+(crypt-222)][(Eind)GeBr2]-, which has been structurally characterized.
RESUMO
Taking advantage of the outstanding oxygen-sensitive luminescence properties of the previously synthesised Tb(iii) complex [{(MeMeArO)3tacn}LnIII(THF)] (1Tb, Ln = Tb), herein, we have prepared an oxygen sensor based on 1Tb embedded in polystyrene film (1Tb/PS) and found that 1Tb/PS shows the highest sensitivity (I0/I100 = 14.9) and the fastest response (response/recovery time = 1.9 s/2.9 s), among the lanthanide(iii)-based oxygen sensors with f-f emission. Moreover, we have prepared the lanthanide(iii)-based colorimetric luminescent oxygen sensor (1TbSm/PS) with green-yellow-red responses, by using 1Tb and a newly synthesised oxygen-insensitive Sm(iii) complex (1Sm, Ln = Sm; Φ = 0.010 and τ = 12.2 µs).
RESUMO
We report the first example of a wholly inorganic mimic of a part of the FeMoco active centre of nitrogenases. We detail the synthesis, characterisation and reactivity of two related, transient hydride-containing inorganic clusters, a dihydride complex and a vinyl monohydride complex, which bear the [Fe2MoOS3] portion of FeMoco. The dihydride complex is capable of reducing acetylene to ethylene via the vinyl monohydride complex. In the reaction cycle, a transient low-valent complex was generated by the reductive elimination of H2 or ethylene from dihydride or vinyl monohydride complexes, respectively.
Assuntos
Acetileno/química , Materiais Biomiméticos/síntese química , Compostos Ferrosos/síntese química , Modelos Químicos , Nitrogenase/química , Materiais Biomiméticos/química , Compostos Ferrosos/química , Estrutura Molecular , Molibdoferredoxina/química , OxirreduçãoRESUMO
Coordination environment of the Tb(3+) ion in oxygen-sensitive luminescent complexes can be successfully controlled through the size of alkyl substituents on ligands {((RMe)ArOH)4cyclen} (R = tBu or Me; cyclen = 1,4,7,10-tetraazacyclododecane); a newly prepared eight-coordinate complex 1(tBu) shows higher oxygen sensitivity (KSV = 17â¯600) and lower luminescence quantum yield (Φ = 0.67 under N2) than those of the previously reported seven-coordinate analogues 1(Me) and [{((MeMe)ArO)3tacn}Tb(III)(THF)] (KSV = 12â¯600 and 8300, Φ = 0.91 and 0.91 under N2, respectively; tacn = 1,4,7-triazacyclononane; THF = tetrahydrofuran). The oxygen-sensitive mechanism is discussed on the basis of the photophysical properties of the corresponding Gd(III) complexes.
RESUMO
This paper presents a gadolinium(iii) complex that shows blue phosphorescence in the crystalline state at room temperature under air atmosphere; color of the crystals can be changed to pale-green from blue by doping of 1-naphthol.
RESUMO
This paper presents the first dysprosium(iii) complex, [{((MeMe)ArO)3tacn}Dy(III)(THF)] (1(Dy)), that shows oxygen-sensitive luminescence. The synthesis, structure and oxygen-sensitive luminescence properties of 1(Dy) are reported (Φ = 0.050 and τ = 17.7 µs under N2, Φ = 0.011 and τ = 4.1 µs under O2 and KSV = 305 M(-1) in THF; KSV = 0.0077%(-1) in polystyrene film). The oxygen sensitive mechanism of 1(Dy) is discussed based on the photophysical properties of the corresponding gadolinium(iii) complex, [{((MeMe)ArO)3tacn}Gd(III)(THF)].
RESUMO
Rod-like millimetre-size crystals of a newly prepared rhodium dithionite complex with n-pentyl moieties bend upon photoirradiation and return to the initial shape upon heating; the roles of the flexible n-pentyl moieties as well as the photoreactive dithionite unit (µ-O2SSO2) are disclosed by single crystal X-ray diffraction.
RESUMO
Dioxygen-tolerant [NiFe] hydrogenases catalyze not only the conversion of H2 into 2 H(+) and 2 e(-) but also the reduction of O2 to H2O. Chemists have sought to mimic such bifunctional catalysts with structurally simpler compounds to facilitate analysis and improvement. Herein, we report a new [NiFe]-based catalyst for O2 reduction via an O2 adduct. Structural investigations reveal the first example of a side-on iron(IV) peroxo complex.
Assuntos
Ferro/química , Oxigênio/química , Hidrogenase/química , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria InfravermelhoRESUMO
We report an acid-stable Si oxide-doped Ir oxide film (IrSi oxide film), made by metal organic chemical vapour deposition (MOCVD) of an Ir(V) complex for electrochemical water-oxidation. This is a successful improvement of catalytic ability and stability depending upon the pH of Ir oxide by doping of Si oxide. The turnover frequency (TOF) of the electrochemical water-oxidation by the IrSi oxide film is the highest of any Si oxide-doped Ir oxide materials and higher even than that of Ir oxide in acidic media.