2,337 research outputs found
Methyl 5-bromo-6-methylpicolinate
The title compound, C8H8BrNO2, does not show any significant intermolecular π–π or C—H⋯π interactions in the crystal packing except for one weak Br⋯Br [3.715 (1) Å] interaction
Three-body molecules - understanding the nature of , , and
The nature of the three pentaquark states, , and
, discovered by the LHCb Collaboration in 2019, is still under
debate, although the molecular interpretation
seems to be the most popular. In this work, by adding a meson into
the pair, we investigate the mass and decay width of
the three-body molecules and explore the
correlation between the existence of the
molecules with the existence of and
two-body molecules. The latter can be identified with
the doubly charmed tetraquark state recently discovered by the LHCb
Collaboration. Based on the molecular nature of , ,
, and , our results indicate that there exist two
three-body bound states of with
and , and binding energies
MeV and MeV below the mass threshold.
In addition, we find that the mass splitting of these two three-body molecules
are correlated to the mass splitting of and , which
offers a non-trivial way to reveal the molecular nature of these states. The
partial widths of two molecules decaying into
and are found to be several MeV.
We recommend the experimental searches for the
molecules in the and
invariant mass distributions
Prevalence of Helicobacter pylori Infection in High-school Students on Lanyu Island, Taiwan: Risk Factor Analysis and Effect on Growth
Background/PurposeThe Yami inhabit Lanyu Island and are the smallest and most primitive aboriginal tribe in Taiwan. Lanyu Island is a closed environment and little information is available on the prevalence of Helicobacter pylori infection there. This study aimed to establish the prevalence of H. pylori infection in high-school students on Lanyu Island and its risk factors and effect on growth.MethodsA cross-sectional population-based study was conducted among high-school students to determine the prevalence of H. pylori infection by using the 13C urea breath test. A questionnaire was administered to the recruited population. Relevant personal and socioeconomic data for risk factors of infection were collected. Body height and weight of the recruited adolescents in relation to H. pylori infection were analyzed.ResultsA total of 106 high-school students (55 boys and 51 girls), with a mean age of 14.3 ± 1.4 years were enrolled. The overall prevalence of H. pylori infection was 54.7%. Those residing in Dongcing village had the highest rate of H. pylori infection (73.3%). There was no difference in the prevalence of H. pylori infection according to sex, ethnicity, socioeconomic level or parental education. Sixty-two students (54.8%) were completely asymptomatic and the others had at least one gastrointestinal symptom. H. pylori infection was asymptomatic in 56.8% and symptomatic in 53.2% of students. There was no significant difference between infected and uninfected children with regard to body weight, height and body mass index.ConclusionThe prevalence of H. pylori infection is high among high-school students on Lanyu Island. There is no evidence that infection is related to growth failure
Ethyl 1-[(4-acetyl-2-methoxyphenoxy)methyl]cyclopropane-1-carboxylate
In the title compound, C16H20O5, the dihedral angle between the planar rings, viz. benzene and cyclopropane, is 52.1 (2)°. Molecules are connected in the crystal via weak intermolecular C—H⋯O hydrogen bonds, forming chains in the [001] direction
Light Harvesting Mechanism of Photosystem II in Photosynthesis:
As one of the most important chemical reactions on the earth, the photosynthetic reaction has gained much attention. For example, foliage and algae possess superior abilities to harvest luminous energy from sunlight in photosynthetic reactions by capturing lights with the light-harvesting complex (LHC) and transferring the energy from LHC to the reaction center (RC) in Photosystem II (PSII), to realize the continuous and efficient transformation from luminous energy to chemistry energy. In this article, the progresses in the studies on the crystal structure of PSII, the energy and electron transfer mechanism, and artificial simulation on photo-induced electron transfer are reviewed. Additionally, the initiating mechanism of hydrogen-abstraction photoinitiators, and the inspiration of the principles and mechanisms of photo-induced electron transfer in macromolecular photoinitiators were also discussed. It is believed that properly choosing covalent chains of appropriate types and length as the bridge between electron donor and electron acceptor is crucial for improving the initiating efficiency of photoinitiators. Keywords: photosynthesis; photosystem; light harvesting; photoinitiator; electron transfe
Efficient synthesis of Vitamin D3 in a 3D ultraviolet photochemical microreactor fabricated using an ultrafast laser
Large-scale, high-precision, and high-transparency microchannels hold great
potential for developing high-performance continuous-flow photochemical
reactions. We demonstrate ultrafast laser-enabled fabrication of 3D
microchannel reactors in ultraviolet (UV) grade fused silica which exhibit high
transparency under the illumination of UV light sources of wavelengths well
below 300 nm with excellent mixing efficiency. With the fabricated glass
microchannel reactors, we demonstrate continuous-flow UV photochemical
synthesis of vitamin D3 with low power consumption of the UV light sources
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