A biradical with ferromagnetic intramolecular interaction was found to improve the SCM behavior of a nitronyl nitroxide-Cu-Dy chain, resulting in an energy barrier for magnetization reversal of 40 K.
Employing the new nitronyl nitroxide biradical ligand biNIT-3Py-5-Ph (2-(5-phenyl-3-pyridyl)-bis(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide)), a 16-spin Cu-radical complex, Cu
(biNIT-3Py-5-Ph)
...(hfac)
, and three 2p-3d-4f chain complexes, {Ln(hfac)
Cu(hfac)
(biNIT-3Py-5-Ph)
}
(Ln
= Gd
, Tb
, Dy
; hfac = hexafluoroacetylacetonate), have been prepared and characterized. X-ray crystallographic analysis revealed in all derivatives a common cyclic Cu-biNIT
secondary building unit in which two bi-NIT-3Py-5-Ph biradical ligands and two Cu
ions are associated via the pyridine N atoms and NO units. For complex
, two such units assemble with four additional Cu
ions to form a discrete complex involving 16
= 1/2 spin centers. For complexes
-
, the Cu-biNIT
units are linked by Ln
ions via NO groups in a 1D coordination polymer. Magnetic studies show that the coordination of the aminoxyl groups with Cu or Ln ions results in behaviors combining ferromagnetic and antiferromagnetic interactions. No slow magnetic relaxation behavior was observed for Tb and Dy derivatives.
The 1:1:2 mixture of Ln(hfac)3, Zn(hfac)2, and NIT‐Pyrim (hfac = hexafluoroacetylacetonate, NIT‐Pyrim = 2‐pyrimidine‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide) afforded a series of 2p‐3d‐4f ...magnetic chains Ln(hfac)3Zn(hfac)2(NIT‐Pyrim)2 LnIII = Gd (1), Ho (2), Yb (3), in which Zn(hfac)2 and Ln(hfac)3 units are bridged by pyrimidine substituted nitronyl nitroxides through their NO moieties and pyrimidine nitrogen atoms. These complexes represent the first examples of 2p‐3d‐4f complexes with ZnII ions. Magnetic studies show that there exist ferromagnetic exchange couplings between the coordinated NO groups of radical ligands and the GdIII ions.
Heterogeneous, metal, single‐site catalysts often exhibit higher catalytic performance than other catalysts because of their maximized atom efficiency of 100 %. Reported herein is a ...precoordination/solvothermal polymerization strategy to fabricate a stable mononuclear Pd‐metalized porous organic polymer catalyst (Pd@POP). Pd@POP was easy to use in regioselective organic reactions because the internal structure of this Pd@POP can be easily modified. The catalyst was used to solve the intractable regioselectivity problems of Heck reactions. Pd@POP‐9 can efficiently activate the ends of olefins, thereby leading to high selectivity for substitution at the external position. To understand the reason underlying the high selectivity and activity of the catalyst, the systemic characterization of Pd@POP‐9 and density‐functional theory calculations were conducted. This Heck reaction is the first to be catalyzed by a recyclable mononuclear metal catalyst with unprecedented catalytic activity and regioselectivity.
Pop around: Reported herein is a precoordination/solvothermal polymerization strategy to fabricate a stable atomically dispersed mononuclear Pd‐metalized N‐heterocyclic carbene doped porous organic polymer catalyst (Pd@POP). This Heck reaction of electronically unbiased alkenes is the first to be catalyzed by a recyclable catalyst (Pd@POP‐9) with unprecedented catalytic activity and regioselectivity.
A novel coronavirus-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-emerged in humans in Wuhan, China, in December 2019 and has since disseminated globally
. As of April 16, 2020, the ...confirmed case count of coronavirus disease 2019 (COVID-19) had surpassed 2 million. Based on full-genome sequence analysis, SARS-CoV-2 shows high homology to SARS-related coronaviruses identified in horseshoe bats
. Here we show the establishment and characterization of expandable intestinal organoids derived from horseshoe bats of the Rhinolophus sinicus species that can recapitulate bat intestinal epithelium. These bat enteroids are fully susceptible to SARS-CoV-2 infection and sustain robust viral replication. Development of gastrointestinal symptoms in some patients with COVID-19 and detection of viral RNA in fecal specimens suggest that SARS-CoV-2 might cause enteric, in addition to respiratory, infection
. Here we demonstrate active replication of SARS-CoV-2 in human intestinal organoids and isolation of infectious virus from the stool specimen of a patient with diarrheal COVID-19. Collectively, we established the first expandable organoid culture system of bat intestinal epithelium and present evidence that SARS-CoV-2 can infect bat intestinal cells. The robust SARS-CoV-2 replication in human intestinal organoids suggests that the human intestinal tract might be a transmission route of SARS-CoV-2.
Two lanthanide single-molecule magnets (SMMs) Dy3(μ3-OH)(HL-1)3(H2O)3(NO3)2·3H3O (1, H3L-1 = (E)-3-(((8-hydroxyquinolin-2-yl)methylene)amino)propane-1,2-diol) and Dy6(μ3-OH)4(H2L-2)4(HL-2)2(L-2)2 (2, ...H3L-2 = (E)-2-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide) were synthesized and characterized structurally and magnetically. Complex 1 contains a triangular Dy3 core in which the three Dy3+ ions share a μ3-OH− anion and the deprotonated ligands of (HL-1)2− serve both capping and bridging functions, while 2 displays a centrosymmetric hexanuclear DyIII structure with two similar Dy3 triangular cores ligated by two fully deprotonated (L-2)3− ligands, each of which shares two μ3-OH− anions. All the DyIII ions are eight-coordinated with quasi D2d or C2v symmetry. Magnetic studies reveal that 1 exhibited two-step magnetic relaxation under an applied dc field of 800 Oe, with effective energy barriers of 40.1 and 31.0 K for the slow relaxation (SR) and fast relaxation regimes (FR), respectively. Meanwhile, 2 only showed a tail of slow magnetic relaxation at above 2 K. Ab initio calculations have been carried out to show the nature of their different magnetic properties.
Four novel heptanuclear Ln-Cu complexes with the formula Ln
2
Cu(hfac)
8
(NITPhTzbis)
2
LnCu(hfac)
5
(NITPhTzbis)
2
(LnCu = YCu
1
, TbCu
2
, DyCu
3
and HoCu
4
; hfac = hexafluoroacetylacetonate) were ...successfully constructed by employing the triazole functionalized nitronyl nitroxide biradical ligand NITPh-Tzbis (NITPh-Tzbis = 5-(1,2,4-triazolyl)-1,3-bis(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl-4,5-hydro-1
H
-imidazol-2-yl)benzene). These hetero-tri-spin complexes are composed of two biradical-bridged dinuclear (LnCu(hfac)
5
(NITPhTzbis) units and one trinuclear Ln
2
Cu(hfac)
8
(NITPhTzbis)
2
unit which form a heptanuclear supramolecular structure through π-π interactions. Magnetic susceptibility investigations indicate that ferromagnetic exchange interactions dominate at low temperature for this supramolecular system which can be attributed to the Ln-nitroxide exchange and intramolecular NIT NIT coupling mediated by the
m
-phenylene moiety. The DyCu derivative was found to exhibit a slow magnetic relaxation behavior.
Supramolecular heptanuclear 2p-3d-4f complexes have been achieved using a nitronyl nitroxide biradical and the CuDy analogue exhibits magnetic relaxation behavior.
This paper integrates a novel primary-side regulation (PSR) scheme with a single-stage high-power-factor (PF) ac-dc light-emitting-diode (LED) driving circuit. The driving circuit is based on the ...combination of a buck-boost PF corrector and a flyback converter. The component amount, cost, and size can be significantly reduced by replacing the secondary-side regulation with the PSR. In this way, not only high performance but also low cost and small system size can be achieved. Above 0.97 PF and 82% efficiency are obtained from a 12-W (60 W replaced) LED bulb driver prototype.
Increasing awareness of climate change and food security has spawned an interest in low-carbon agriculture, an important aspect of which is the reduction of greenhouse gas emissions. As the largest ...source of agricultural emissions is fertilizer application, using a different type of fertilizer may help to mitigate greenhouse gas emissions from agriculture systems. The objectives of this study were to report a basic estimate of agricultural inputs and greenhouse gas emissions of crop production using national statistical data available for the period of 1993–2007, to compare the quantities of greenhouse gas emissions from different fertilizer types (per unit of N, P2O5, and K2O), to identify fertilizer types with the lowest emissions and the lowest costs, and to quantify the emissions gap between the lowest and actual emission scenarios, which will provide critical information for pursuing low-carbon agriculture in the future. According to available data, the use of all agricultural inputs increased during 1993–2012, resulting in an increase in not only yield but also in total greenhouse gas emissions from crop production. Not considering direct N2O emissions from the field, fertilizer-induced emissions accounted for up to 47.71% of the total greenhouse gas emissions from crop production. Therefore, lowering fertilizer-induced emissions is a priority measure that will result in low-carbon agriculture. Furthermore, ammonium bicarbonate, calcium superphosphate, and potassium chloride were found to be fertilizers with the lowest greenhouse gas emissions, and adoption of these fertilizers would result in a 49.15% reduction in fertilizer-induced emissions. This finding indicates that the judicious choice of fertilizer type would contribute to reducing greenhouse gas emissions in intensive production systems in China. Accordingly, utilizing ammonium bicarbonate, calcium superphosphate, and potassium chloride would be beneficial for greenhouse gas emission reduction and could be adopted as a good practice of low-carbon agriculture in China. This study highlights that changing to an appropriate fertilizer type could be an efficient option for mitigating greenhouse gas emissions in crop production in China.
•GHG emissions from different types of fertilizer products were compared.•The lowest emissions of the N, P, and K fertilizers were identified, respectively.•Adoption of the lowest emissions result in a 49% reduction of fertilizer emissions.
Respective detection of microplastics (MPs) and nanoplastics (NPs) is of great importance for their different environmental behaviors and toxicities. Using spherical polystyrene (PS) and poly(methyl ...methacrylate) (PMMA) plastics as models, the efficiency for sequential isolation of MPs and NPs by membrane filtration and cloud-point extraction was evaluated. After filtering through a glass membrane (1 μm pore size), over 90.7% of MPs were trapped on the membrane, whereas above 93.0% of NPs remained in the filtrate. The collected MPs together with the glass membrane were frozen in liquid nitrogen, ground, and suspended in water (1 mL) and subjected to pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) determination. The NPs in the filtrate were concentrated by cloud-point extraction, heated at 190 °C to degrade the extractant, and then determined by Py-GC/MS. For MPs and NPs spiked in pure water, the method detection limits are in the range of 0.05–1.9 μg/L. The proposed method is applied to analyze four real water samples, with the detection of 1.6–7.6 μg/L PS MPs and 0.6 μg/L PMMA MPs in three samples, and spiked recoveries of 75.0–102% for MPs and 67.8–87.2% for NPs. Our method offers a novel sample pretreatment approach for the respective determination of MPs and NPs.
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