3,309 research outputs found
Rapid Global Spread of the SARS-CoV-2 Delta (B.1.617.2) Variant: Spatiotemporal Variation and Public Health Impact
The COVID-19 pandemic has already affected human society for more than 1.5 years. As of August 8, 2021, this pandemic had caused more than 203 million infected and 4.3 million deaths worldwide. As an RNA virus, SARS-CoV-2 is prone to genetic evolution, thus resulting in development of mutations over time. Numerous variants of SARS-CoV-2 have been described globally, four of which are considered variants of concern (VOCs) by the WHO: Alpha (B.1.1.7), Beta (B.1.351), Gamma (P1) and Delta (B.1.617.2). The Delta VOC was first reported in India in December of 2020 and has since affected approximately 130 different countries and regions. Herein, the spatiotemporal spread of the Delta VOC during April to July 2021 in 20 selected countries with available data were analyzed. The prevalence of the Delta VOC sequences was maintained at low levels in the beginning of April, increased rapidly in the following 3 months and is now becoming the predominant viral strain in most regions of the world. We also discuss the effects of the Delta VOC on transmissibility, clinical severity and vaccine effectiveness according to the latest data. The Delta VOC has greater transmissibility and risk of hospitalization than the ancestral SARS-CoV-2 strains and the other three VOCs. The Delta VOC places partially or unvaccinated sub-populations at high risk. Currently authorized vaccines, regardless of vaccine type, still have reliable effectiveness against symptomatic infections and hospitalizations due to the Delta VOC
The linear and nonlinear Jaynes-Cummings model for the multiphoton transition
With the Jaynes-Cummings model, we have studied the atom and light field
quantum entanglement of multiphoton transition, and researched the effect of
initial state superposition coefficient , the transition photon number
, the quantum discord and the nonlinear coefficient on the
quantum entanglement degrees. We have given the quantum entanglement degrees
curves with time evolution, and obtained some results, which should have been
used in quantum computing and quantum information.Comment: arXiv admin note: text overlap with arXiv:1404.0821, arXiv:1205.0979
by other author
Study of pentaquark system in the Chiral Quark Model
With the discovery of some hidden-charm pentaquark resonances by the LHCb
Collaboration, investigations of pentaquark states containing heavy quarks have
aroused the interest of theorists. We study herein ( or
, or ) pentaquark system, in the framework of the chiral quark
model. In consequence, some charmed and bottomed pentaquarks are considered to
exist by five-body dynamical calculations. In the charm sector,
and are
possible candidates of and , respectively.
Besides, two high-spin states, and
, are also found in the energy region of GeV. In the bottom sector, ,
could be candidates of
and , respectively. And
and are found in the energy region of GeV. and are expected as
compact states, while , , and
are expected as molecular states.Comment: 11 pages, 1 figur
ELISA and chemiluminescent enzyme immunoassay for sensitive and specific determination of lead (II) in water, food and feed samples
Lead is a heavy metal with increasing public health concerns on its accumulation in the food chain and environment. Immunoassays for the quantitative measurement of environmental heavy metals offer numerous advantages over other traditional methods. ELISA and chemiluminescent enzyme immunoassay (CLEIA), based on the mAb we generated, were developed for the detection of lead (II). In total, 50% inhibitory concentrations (IC50) of lead (II) were 9.4 ng/mL (ELISA) and 1.4 ng/mL (CLEIA); the limits of detection (LOD) were 0.7 ng/mL (ic-ELISA) and 0.1 ng/mL (ic-CLEIA), respectively. Cross-reactivities of the mAb toward other metal ions were less than 0.943%, indicating that the obtained mAb has high sensitivity and specificity. The recovery rates were 82.1%–108.3% (ic-ELISA) and 80.1%–98.8% (ic-CLEIA), respectively. The developed methods are feasible for the determination of trace lead (II) in various samples with high sensitivity, specificity, fastness, simplicity and accuracy.This research was funded by National Natural Science Foundation of China, grant numbers 31572556, 31873006; the Key Program for International S&T Cooperation Project of Shaanxi Province, grant number 2017KW-ZD-10; and the Incubation Project on State Key Laboratory of Biological Resources and Ecological Environment of Qinba Areas, grant number SLGPT2019KF04-04
8-Benzoyl-7-hydroxy-4-methyl-2H-1-benzopyran-2-one monohydrate
In the title compound, C17H12O4·H2O, the coumarin ring system is approximately planar with a maximum atomic deviation of 0.011 (2) Å, and is nearly perpendicular to the phenyl ring at a dihedral angle of 86.63 (9)°. In the crystal, molecules are linked by classical O—H⋯O and weak C—H⋯O hydrogen bonds. π–π stacking is also present [centroid–centroid distance = 3.6898 (12) Å]
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