The Immersed Structural Potential Method for haemodynamic applications

In this paper, a new fluid–structure interaction immersed computational methodology, based upon the original Immersed Boundary Method (IBM) [1] is outlined with the final aim of modelling cardiovascular phenomena, specifically, heart valve related problems. The principal characteristic of such immersed techniques is the representation of any deformable or rigid body immersed within an incompressible viscous flow field as a momentum forcing source in the Navier–Stokes equations. A number of shortcomings within the immersed formulation still require further investigation and improvement, including the excessive numerical diffusion caused by the interpolation/spreading process, the need to include realistic viscoelastic composite constitutive models describing more accurately the nature of cardiovascular tissues and also the need to capture more effectively stresses developed at the fluid–structure interface. By following the same philosophy as the original IBM, a more sophisticated formulation is derived in this paper, the “Immersed Structural Potential Method (ISPM)”. The method introduced presents an alternative approach to compute the equivalent fluid–structure interaction forces at the fluid mesh, accounts for a sophisticated viscoelastic fibre-reinforced constitutive model to better describe the mechanics of cardiovascular tissues and utilises a novel time-integration methodology for the computation of the deformation gradient tensor which ensures compliance with the incompressibility constraint. A series of numerical examples will be presented in order to demonstrate the robustness and applicability of this new methodology.     

3D polarimetric purity

From our previous definition of the indices of polarimetric purity for 3D light beams [J.J. Gil, J.M. Correas, P.A. Melero and C. Ferreira, Monogr. Semin. Mat. G. de Galdeano 31, 161 (2004)], an analysis of their geometric and physical interpretation is presented. It is found that, in agreement with previous results, the first parameter is a measure of the degree of polarization, whereas the second parameter (called the degree of directionality) is a measure of the mean angular aperture of the direction of propagation of the corresponding light beam. This pair of invariant, non-dimensional, indices of polarimetric purity contains complete information about the polarimetric purity of a light beam. The overall degree of polarimetric purity is obtained as a weighted quadratic average of the degree of polarization and the degree of directionality.     

Dynamic imaging with MRI contrast agents: quantitative considerations

Time-resolved MRI has had enormous impact in cognitive science and may become a significant tool in basic biological research with the application of new molecular imaging agents. In this paper, we examine the temporal characteristics of MRI contrast agents that could be used in dynamic studies. We consider "smart" T1 contrast agents, T2 agents based on reversible aggregation of superparamagnetic nanoparticles and sensors that produce changes in saturation transfer effects (chemical exchange saturation transfer, CEST). We discuss response properties of several agents with reference to available experimental data, and we develop a new theoretical model that predicts the response rates and relaxivity changes of aggregation-based sensors. We also perform calculations to define the extent to which constraints on temporal resolution are imposed by the imaging methods themselves. Our analysis confirms that some small T1 agents may be compatible with MRI temporal resolution on the order of 100 ms. Nanoparticle aggregation T2 sensors are applicable at much lower concentrations, but are likely to respond on a single second or slower timescale. CEST agents work at high concentrations and temporal resolutions of 1-10 s, limited by a requirement for long presaturation periods in the MRI pulse sequence.     

Cancellation of Raman pulse walk-off by slow light

We theoretically demonstrate in a nonlinear optical fiber system with a narrowband Raman gain that pulse walk-off between the pump and the Raman Stokes waves can be fully compensated for by Raman slow light, leading to group-velocity matching between the interacting waves, greater useful interaction length, and thereby enhanced Raman amplification efficiency. Limitations due to Kerr effect are further discussed.     

Changes in mouse Leydig cells ultrastructure and testosterone secretion after diethylcarbamazine administration

Diethylcarbamazine (DEC) has been proven to be highly effective against lymphatic filariasis, although its effect on vertebrate cells remains uncertain. Mice Leydig cells after treatment with 200mg/kg of DEC for 12 days showed numerous lipid droplets, degenerated mitochondria, residual bodies and several giant whorl-like smooth endoplasmic reticulum, some of them encircling large lipids droplets. Treatment with lower dosages showed similar alterations on Leydig cells and the morphological effects decreased directly proportional to the drug concentration. Serum testosterone levels were significantly lower only in 200 mg/kg DEC-treated group when compared to the controls. However, no significant changes were observed in the pregnancy rates and offspring number of DEC-treated male-mated female mice in any doses studied. The results obtained in the present study are consistent with the hypothesis that DEC has some effects on mice Leydig cells, although they were not sufficient enough to interfere with the rodent fertility.     

Some Comments on “The Mathematical Universe”

I discuss some problems related to extreme mathematical realism, focusing on a recently proposed “shut-up-and-calculate” approach to physics (Tegmark in Found. Phys. 38:101, 2008; New Sci., September 15th, 2007). I offer arguments for a moderate alternative, the essence of which lies in the acceptance that mathematics is (at least in part) a human construction, and discuss concrete consequences of this—at first sight purely philosophical—difference in point of view.     

Aromatic butenolides produced by a soil ascomycete Auxarthron sp. KCB15F070 derived from a volcanic island

LC/MS-based chemical screening of fungal extract fraction library led to identification of three 2,3-aryl substituted furanone metabolites (1–3), including one known butenolide glycoside (1) whose stereochemistry remained unsolved and two new compounds gotjawaside and gotjawalide (2 and 3), from Auxarthron sp. KCB15F070, a fungus isolated from a soil sample of the volcanic island Jeju, Korea. Their planar structures were elucidated by 1D- and 2D-NMR spectroscopic and HRESIMS spectrometric techniques, and the absolute configurations of three compounds were solved using a combination of chemical derivatizations and computational analysis of vibrational circular dichroism (VCD) spectra.     

Structural and Optical Properties of Zn1‐xMgxO Prepared by Calcination of ZnO + Mg(OH)2 after Hydro Micro Mechanical Activation

Zn_1‐xMg_xO microcrystals are produced in the 0.15 ≤ x ≤ 1 composition range by calcination of ZnO + Mg(OH)₂ after hydro micro mechanical activation according to the patent WO2018065735A1. The structural properties of the samples have revealed the cohabitation of wurtzite and rock‐salt phases for x values ranging from 0.15 up to 0.6 with a clear increase of the proportion of cubic phase with x. A single cubic phase is observed in the range 0.66 ≤ x < 1. From the purity of these samples produced at very low cost, it is expected that they will be used as precursors for growth of advanced light emitters integrated into an already existing process as they exhibit exceptionally efficient (and robust with T) light emission in the ultraviolet region.     

Argon K-shell and bound-free emission from OMEGA direct-drive implosion cores

We discuss calculations of synthetic spectra for the interpretation and analysis of K-shell and bound-free emission from argon-doped deuterium-filled OMEGA direct-drive implosion cores. The spectra are computed using a model that considers collisional-radiative atomic kinetics, continuum-lowering, detailed Stark-broadened line shapes, line overlapping, and radiation transport effects. The photon energy range covers the moderately optically thick n = 3 → n = 1 and n = 4 → n = 1 line transitions in He- and H-like Ar, their associated satellite lines in Li- and He-like Ar, and several radiative recombination edges. At the high-densities characteristic of implosion cores, the radiative recombination edges substantially shift to lower energies thus overlapping with several line transitions. We discuss the application of the spectra to spectroscopic analysis of doped implosion cores.     

Cu2+-selective turn-on fluorescence signaling based on metal-induced hydrolysis of pyrenecarbohydrazide

We developed a simple Cu²⁺-selective turn-on fluorescence signaling probe based on the hydrolysis of 1-pyrenecarbohydrazide (1) to 1-pyrenecarboxylic acid. Probe 1 exhibited prominent fluorescence signaling of Cu²⁺ ions in a 10% aqueous Tris-buffered (pH 7.0) DMSO solution with a detection limit of 5.93 × 10^?8 M. Signaling with control compounds derived from pyreneacetic acid and pyrenebutyric acid showed that the fluorescence signal became less pronounced as the distance between the hydrazide functionality and the pyrene fluorophore increased. As a practical application, this probe was employed for the determination of Cu²⁺ in a simulated semiconductor wastewater.