6 research outputs found
Regioselective Synthesis of Indole-Fused Seven-Membered N‑Heterocycles via Photoredox-Catalyzed Intramolecular Cyclization
Herein, we describe the construction of indole-fused
seven-membered
N- and O-heterocycles from indolyl α-diazocarbonyls via photoredox-catalyzed
intramolecular cyclization. The photoredox process features operational
simplicity, mild conditions, and as low as 0.1 mol % catalyst loading.
The tricyclic heterocycles are obtained in yields of 24 to 67% with
excellent regioselectivity. The practicality of this protocol is further
demonstrated by gram-scale reactions carried out in both batch and
continuous flow
Gold Nanorods as Colorful Chromogenic Substrates for Semiquantitative Detection of Nucleic Acids, Proteins, and Small Molecules with the Naked Eye
Herein,
we report for the first time a colorful chromogenic substrate, which
displays vivid color responses in the presence of different concentration
of analytes. Our investigation reveals that the selective shortening
of gold nanorods (AuNRs) could generate a series of distinct colors
that covers nearly the whole visible range from 400 to 760 nm. These
vivid colors can be easily distinguished by the naked eye; as a result,
the accuracy of visual inspection could be greatly improved. Next,
we demonstrate the utility of AuNRs as multicolor chromogenic substrate
to develop a number of colorimetric immunoassay methods, e.g., multicolor
enzyme-linked immunosorbent assay (ELISA), multicolor competitive
ELISA, and multicolor magnetic immunoassay (MIA). These methods allow
us to visually quantify the concentration of a broad range of target
molecules with the naked eye, and the obtained results are highly
consistent with those state-of-the-art techniques that are tested
by the sophisticated apparatus. These multicolor portable and cost-effective
immunoassay approaches could be potentially useful for a number of
applications, for example, in-home personal healthcare, on-site environmental
monitoring, and food inspection in the field
One-Pot Synthesis of Multisubstituted Butyrolactonimidates: Total Synthesis of (−)-Nephrosteranic Acid
Multisubstituted
chiral butyrolactonimidates have been synthesized
via a one-pot, three-step cascade reaction in which (<i>R</i>)-<i>N</i>-<i>tert</i>-butanesulfinyl imidates
and α,β-unsaturated diesters undergo highly stereoselective
Michael addition, anion-oxidative hydroxylation, and cyclization.
The synthesized butyrolactonimidates are versatile intermediates for
preparation of substituted butyrolactones and furans. The usefulness
of this cascade reaction is demonstrated through the concise total
synthesis of natural product (−)-nephrosteranic acid
One-Pot Synthesis of Multisubstituted Butyrolactonimidates: Total Synthesis of (−)-Nephrosteranic Acid
Multisubstituted
chiral butyrolactonimidates have been synthesized
via a one-pot, three-step cascade reaction in which (<i>R</i>)-<i>N</i>-<i>tert</i>-butanesulfinyl imidates
and α,β-unsaturated diesters undergo highly stereoselective
Michael addition, anion-oxidative hydroxylation, and cyclization.
The synthesized butyrolactonimidates are versatile intermediates for
preparation of substituted butyrolactones and furans. The usefulness
of this cascade reaction is demonstrated through the concise total
synthesis of natural product (−)-nephrosteranic acid
High-Quality GaN Epilayers Achieved by Facet-Controlled Epitaxial Lateral Overgrowth on Sputtered AlN/PSS Templates
It
is widely believed that the lack of high-quality GaN wafers severely
hinders the progress in GaN-based devices, especially for defect-sensitive
devices. Here, low-cost AlN buffer layers were sputtered on cone-shaped
patterned sapphire substrates (PSSs) to obtain high-quality GaN epilayers.
Without any mask or regrowth, facet-controlled epitaxial lateral overgrowth
was realized by metal–organic chemical vapor deposition. The
uniform coating of the sputtered AlN buffer layer and the optimized
multiple modulation guaranteed high growth selectivity and uniformity
of the GaN epilayer. As a result, an extremely smooth surface was
achieved with an average roughness of 0.17 nm over 3 × 3 μm<sup>2</sup>. It was found that the sputtered AlN buffer layer could significantly
suppress dislocations on the cones. Moreover, the optimized three-dimensional
growth process could effectively promote dislocation bending. Therefore,
the threading dislocation density (TDD) of the GaN epilayer was reduced
to 4.6 × 10<sup>7</sup> cm<sup>–2</sup>, which is about
an order of magnitude lower than the case of two-step GaN on the PSS.
In addition, contamination and crack in the light-emitting diode fabricated
on the obtained GaN were also effectively suppressed by using the
sputtered AlN buffer layer. All of these advantages led to a high
output power of 116 mW at 500 mA with an emission wavelength of 375
nm. This simple, yet effective growth technique is believed to have
great application prospects in high-performance TDD-sensitive optoelectronic
and electronic devices
Data_Sheet_1_The role of meteorological factors on influenza incidence among children in Guangzhou China, 2019–2022.docx
ObjectiveAnalyzing the epidemiological characteristics of influenza cases among children aged 0–17 years in Guangzhou from 2019 to 2022. Assessing the relationships between multiple meteorological factors and influenza, improving the early warning systems for influenza, and providing a scientific basis for influenza prevention and control measures.MethodsThe influenza data were obtained from the Chinese Center for Disease Control and Prevention. Meteorological data were provided by Guangdong Meteorological Service. Spearman correlation analysis was conducted to examine the relevance between meteorological factors and the number of influenza cases. Distributed lag non-linear models (DLNM) were used to explore the effects of meteorological factors on influenza incidence.ResultsThe relationship between mean temperature, rainfall, sunshine hours, and influenza cases presented a wavy pattern. The correlation between relative humidity and influenza cases was illustrated by a U-shaped curve. When the temperature dropped below 13°C, Relative risk (RR) increased sharply with decreasing temperature, peaking at 5.7°C with an RR of 83.78 (95% CI: 25.52, 275.09). The RR was increased when the relative humidity was below 66% or above 79%, and the highest RR was 7.50 (95% CI: 22.92, 19.25) at 99%. The RR was increased exponentially when the rainfall exceeded 1,625 mm, reaching a maximum value of 2566.29 (95% CI: 21.85, 3558574.07) at the highest rainfall levels. Both low and high sunshine hours were associated with reduced incidence of influenza, and the lowest RR was 0.20 (95% CI: 20.08, 0.49) at 9.4 h. No significant difference of the meteorological factors on influenza was observed between males and females. The impacts of cumulative extreme low temperature and low relative humidity on influenza among children aged 0–3 presented protective effects and the 0–3 years group had the lowest RRs of cumulative extreme high relative humidity and rainfall. The highest RRs of cumulative extreme effect of all meteorological factors (expect sunshine hours) were observed in the 7–12 years group.ConclusionTemperature, relative humidity, rainfall, and sunshine hours can be used as important predictors of influenza in children to improve the early warning system of influenza. Extreme weather reduces the risk of influenza in the age group of 0–3 years, but significantly increases the risk for those aged 7–12 years.</p