Enhanced sensitivity of hemoglobin sensor using dual-core photonic crystal fiber

A Hemoglobin (Hb) biosensor based on dual-core photonic crystal fiber is proposed and analyzed. In this paper, the effective refractive index dependency on the Hb concentration within a blood sample is utilized in obtaining the transmission spectrum variation. The results are calculated using full vectorial finite element method. Through this study, the effect of the structure geometrical parameters on the sensor performance is optimized to maximize the sensor sensitivity. The numerical results show a sensitivity of 8.013 nm/g/dL for the X-polarized mode at 3.7 cm fiber length and 7.68 nm/g/dL for the Y-polarized mode at 3.2 cm fiber length of the proposed sensor.     

Nonaxisymmetric radiative transfer in inhomogeneous cylindrical media with anisotropic scattering

In this paper, the control volume finite element method (CVFEM) is applied for the first time to solve nonaxisymmetric radiative transfer in inhomogeneous, emitting, absorbing and anisotropic scattering cylindrical media. Mathematical formulations as well as numerical implementation are given and the final discretized equations are based on similar meshes used for convective and conductive heat transfer in computational fluid dynamic analysis. In order to test the efficiency of the developed method, four nonaxisymmetric problems have been examined. Also, the grid dependence and the false scattering of the CVFEM are investigated and compared with the finite volume method and the discrete ordinates interpolation method.     

Dynamic evolution of double $$\Lambda $$ five-level atom interacting with one-mode electromagnetic cavity field

In this paper, the model describing a double \(\Lambda \) five-level atom interacting with a single mode electromagnetic cavity field in the (off) non-resonate case is studied. We obtained the constants of motion for the considered model. Also, the state vector of the wave function is given by using the Schrödinger equation when the atom is initially prepared in its excited state. The dynamical evolutions for the collapse revivals, the antibunching of photons and the field squeezing phenomena are investigated when the field is considered in a coherent state. The influence of detuning parameters on these phenomena is investigated. We noticed that the atom–field properties are influenced by changing the detuning parameters. The investigation of these aspects by numerical simulations is carried out using the Quantum Toolbox in Python (QuTip).     

A self-similar behavior for the relative viscosity of concentrated suspensions of rigid spheroids

A viscosity model for suspensions of rigid particles with predictive capability over a wide range of particle volume fraction and shear conditions is of interest to quantify the transport of suspensions in fluid flow models. We study the shear viscosity of suspensions and focus on the effect of particle aspect ratio and shear conditions on the rheological behavior of suspensions of rigid bi-axially symmetric ellipsoids (spheroids). We propose a framework that forms the basis to microscopically parameterize the evolution of the suspension microstructures and its effect on the shear viscosity of suspensions. We find that two state variables, the intrinsic viscosity in concentrated limit and the self-crowding factor, control the state of dispersion of the suspension. A combination of these two variables is shown to be invariant with the imposed shear stress (or shear rate) and depends only on the particle aspect ratio. This self-similar behavior, tested against available experimental and numerical data, allows us to derive a predictive model for the relative viscosity of concentrated suspensions of spheroids subjected to low (near zero) strain rates. At higher imposed strain rates, one needs to constrain one of the state variables independently to constrain the state of dispersion of the suspension and its shear dynamic viscosity. Alternatively, the obtained self-similar behavior provides the means to estimate the state variables from the viscosity measurements made in the laboratory, and to relate them to microstructure rearrangements and evolution occurring during deformation.     

A conservative stabilized finite element method for the magneto‐hydrodynamic equations

This work presents a finite element solution of the 3D magneto‐hydrodynamics equations. The formulation takes explicitly into account the local conservation of the magnetic field, giving rise to a conservative formulation and introducing a new scalar variable. A stabilization technique is used in order to allow equal linear interpolation on tetrahedral elements of all the variables. Numerical tests are performed in order to assess the stability and the accuracy of the resulting methods. The convergence rates are calculated for different stabilization parameters. Well‐known MHD benchmark tests are calculated. Results show good agreement with analytical solutions. Copyright © 1999 John Wiley & Sons, Ltd.     

Existence and Uniqueness of Solutions for Time-Fractional Oldroyd-B Fluid Equations with Generalized Fractional Derivatives

In this paper, we study the existence and uniqueness of solutions for time-fractional Oldroyd-B fluid equations with generalized fractional derivatives. We distinguish two cases. Firstly for the linear case, we get regularity results under some hypotheses of the source function and the initial data. Secondly for the nonlinear case, we use the Banach fixed point theorem to obtain the existence and uniqueness of solutions.     

Stilbene and 2-arylbenzofuran glucosides from the rhizomes of Schoenocaulon officinale

Two stilbene glucosides, oxyresveratrol 2-O-beta-glucopyranoside and resveratrol 3,4'-O,O'-di-beta-D-glucopyranoside, and a 2-arylbenzofuran glucoside, schoenoside, were isolated from the rhizomes of Schoenocaulon officinale, along with five known compounds, oxyresveratrol 3'-O-beta-D-glucopyranoside, oxyresveratrol, resveratrol 3-O-beta-D-glucopyranoside, mulberroside A and moracin M 3'-O-beta-D-glucopyranoside. The structural elucidations were based on analyses of both physical and spectroscopic data.     

Some reactions with ω-bromoacetophenone: Synthesis of Δαβ-butenolide and its transformation into pyrrole derivatives

ω-Bromoacetophenone reacts with the sodium salt of ethyl cyanoacetate to afford α-cyano-β-phenyl-Δ^αβ-butenolide. This butenolide undergoes azo coupling with diazotized aromatic amines (ArNH₂) to afford the hydrazo derivatives. These hydrazo derivatives (ArPh, 4-ClC₆H₄, 4-MeC₆H₄, 4-MeOC₆H₄) were transformed into the corresponding 3(2H)-pyridazinone derivatives on stirring in methanol in the presence of potassium hydroxide. These latter compounds were converted into the corresponding 3-cyano-2,5-dihydroxy-4-phenyl-N-arylpyrrole derivatives on reduction with zinc dust in refluxing acetic acid, presumably via reductive cleavage of the N N bond of the pyridazine followed by recyclization via loss of ammonia.     

Discovery of SARS-CoV-2 Mpro peptide inhibitors from modelling substrate and ligand binding

The main protease (M^pro) of SARS-CoV-2 is central to viral maturation and is a promising drug target, but little is known about structural aspects of how it binds to its 11 natural cleavage sites. We used biophysical and crystallographic data and an array of biomolecular simulation techniques, including automated docking, molecular dynamics (MD) and interactive MD in virtual reality, QM/MM, and linear-scaling DFT, to investigate the molecular features underlying recognition of the natural M^pro substrates. We extensively analysed the subsite interactions of modelled 11-residue cleavage site peptides, crystallographic ligands, and docked COVID Moonshot-designed covalent inhibitors. Our modelling studies reveal remarkable consistency in the hydrogen bonding patterns of the natural M^pro substrates, particularly on the N-terminal side of the scissile bond. They highlight the critical role of interactions beyond the immediate active site in recognition and catalysis, in particular plasticity at the S2 site. Building on our initial M^pro-substrate models, we used predictive saturation variation scanning (PreSaVS) to design peptides with improved affinity. Non-denaturing mass spectrometry and other biophysical analyses confirm these new and effective ‘peptibitors’ inhibit M^pro competitively. Our combined results provide new insights and highlight opportunities for the development of M^pro inhibitors as anti-COVID-19 drugs.

The main protease (M^pro) of SARS-CoV-2 is central to viral maturation and is a promising drug target. In silico methods reveal structural aspects of how it binds to its 11 natural cleavage sites, the design of novel peptide inhibitors, and insights into drug design.     

[Yb(H2O)8][Cd3Cl9(H2O)]·6H2O

The title compound, namely octa­aqua­ytterbium(III) aqua­nona­chloro­tricadmate(II) hexa­hydrate, [Yb(H₂O)₈][Cd₃Cl₉(H₂O)]·6H₂O, was prepared by evaporation at 278 K from an aqueous solution of the ternary system YbCl₃–CdCl₂–H₂O and was characterized by elemental chemical analysis and by X‐ray powder and single‐crystal diffraction studies. The crystal structure can be viewed as being built from layers of double chains of CdCl₆ and CdCl₅(H₂O) octahedra separated by antiprismatic [Yb(H₂O)₈]³⁺ cations. The stabilization of the structure is ensured by O—H⋯O and O—H⋯Cl hydrogen bonds. A comparison with the structures of SrCd₂Cl₆·8H₂O and CeCd₄Cl₁₁·13H₂O is presented.