The diffusion of novel SARS-CoV-2 coronavirus over the world generated COVID-19 pandemic event as reported by World Health Organization on March 2020. The huge issue is the high infectivity and the absence of vaccine and customised drugs allowing for hard management of this outbreak, thus a rapid and on site analysis is a need to contain the spread of COVID-19. Herein, we developed an electrochemical immunoassay for rapid and smart detection of SARS-CoV-2 coronavirus in saliva. The electrochemical assay was conceived for Spike (S) protein or Nucleocapsid (N) protein detection using magnetic beads as support of immunological chain and secondary antibody with alkaline phosphatase as immunological label. The enzymatic by-product 1-naphtol was detected using screen-printed electrodes modified with carbon black nanomaterial. The analytical features of the electrochemical immunoassay were evaluated using the standard solution of S and N protein in buffer solution and untreated saliva with a detection limit equal to 19 ng/mL and 8 ng/mL in untreated saliva, respectively for S and N protein. Its effectiveness was assessed using cultured virus in biosafety level 3 and in saliva clinical samples comparing the data using the nasopharyngeal swab specimens tested with Real-Time PCR. The agreement of the data, the low detection limit achieved, the rapid analysis (30 min), the miniaturization, and portability of the instrument combined with the easiness to use and no-invasive sampling, confer to this analytical tool high potentiality for market entry as the first highly sensitive electrochemical immunoassay for SARS-CoV-2 detection in untreated saliva.
We discuss the nature of the χ b (3P ) and X(3872) mesons: Are the χ b (3P )'s standard bb mesons or bb states with a significative continuum component? Is the X(3872) a cc state with continuum coupling effects or a meson-meson molecule? To do that, we compare quark model and unquenched quark model results for the mass barycenter and splittings of the χ b (3P ) multiplet. Future and more precise experimental results will discriminate between the two interpretations. In the case of the X(3872), we interpret it a cc core plus higher Fock components due to the coupling to the mesonmeson continuum, thus we think that it is compatible with the meson χc1(2P ), with J P C = 1 ++ . The J P C = 1 ++ quantum numbers are in agreement with the experimental results found by the LHCb collaboration. In our view, the X(3872)'s mass is lower than the quark model's predictions because of self energy shifts. We also provide an estimation of the open charm/bottom strong decay modes of the X(3872) and χ b (3P ) mesons, such as X(3872) → DD * and χ b2 (3P ) → BB, and radiative transitions.
Using the non-relativisitc reduction of Coulomb gauge QCD we compute spectrum of the low mass hybrid mesons containing a heavy quark-antiquark pair. The gluon degrees of freedom are treated in the mean field approximation calibrated to the gluelump spectrum. We discuss the role of the non-abelian nature of the QCD Coulomb interaction in the ordering of the spin-parity levels.
We compute the energy spectrum of gluelumps defined as gluonic excitations bound to a localized, static octet source. We are able to reproduce the nontrivial ordering of the spin-parity levels and show how this is related to the non-abelian part of the Coulomb interaction between color charges.
We provide results for the open-flavor strong decays of strange and non-strange baryons into a baryon-vector/pseudoscalar meson pair. The decay amplitudes are computed in the 3 P0 paircreation model, where ss pair-creation suppression is included for the first time in the baryon sector, in combination with the U(7) and hypercentral models. The effects of this ss suppression mechanism cannot be re-absorbed in a redefinition of the model parameters or in a different choice of the 3 P0 model vertex factor. Our results for the decay amplitudes are compared with the existing experimental data and previous 3 P0 and elementary meson emission model calculations. In this respect, we show that distinct quark models differ in the number of missing resonances they predict and also in the quantum numbers of states. Therefore, future experimental results will be important in order to disentangle different models of baryon structure. Finally, in the appendices, we provide some details of our calculations, including the derivation of all relevant flavor couplings with strangeness-suppression. This derivation may be helpful to calculate the open-flavor decay amplitudes starting from other models of baryons.
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