Revisiting paramagnetic relaxation enhancements in slowly rotating systems: how long is the long range?

Cross relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than one order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation matrix approach. The calculations show that the Solomon dependence of the relaxation rates on the metal-proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal, and thus can originate sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at MRI magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons.

Synthesis, characterization and computational studies of 1,3-bis[(E)-furan-2-yl)methylene]urea and 1,3-bis[(E)-furan-2-yl)methylene]thiourea

Urea and thiourea derivatives: 1,3-bis[(E)-furan-2-yl)methylene]urea (BFMU) and 1,3-bis[(E)-furan-2-yl)methylene]thiourea (BFMT) were synthesized and characterized by spectrometry analyses (UV, IR, 1H NMR and 13C NMR). They were screened for antibacterial (Salmonella typhi, Staphylococcus aureus, Pseudomonas aeruginosa, Xanthomonas axonopodis and Streptococcus bovis) and antifungal (Fusarium oxysporum, Colletotrichum gloeosporioides and Cercospora zeae-maydis) activities. Quantum chemical calculations of frontier molecular orbital energies (EHOMO and ELUMO), and their associated global parameters were carried out by DFT levels of theory, with complete relaxation in the potential energy surface using 6-31G* basis set (DFT/B3LYP/6-31G*). Azomethine functional groups (C=N) appeared at δ 7.6 ppm and δ 7.0 ppm in the proton spectra, the peaks between δ 105 and δ 160 ppm of 13C spectra represent the methylene carbons (C=C). BFMU is a better inhibitor of P. aeruginosa and S. bovis, while BFMT is a better inhibitor of S. typhi, S. aureus and X. axonopodis and the fungi isolates (F. oxysporum, C. gloeosporioides and C. zeae-maydis) used. The global parameters agreed favorably with the experimental results, indicating the higher activity of BFMT.

Modelling optimal vaccination strategy for SARS-CoV-2 in the UK.

The COVID-19 outbreak has highlighted our vulnerability to novel infections. Faced with this threat and no effective treatment, in line with many other countries, the UK adopted enforced social distancing (lockdown) to reduce transmission- successfully reducing the reproductive number, R, below one. However, given the large pool of susceptible individuals that remain, complete relaxation of controls is likely to generate a substantial second wave. Vaccination remains the only foreseeable means of both containing the infection and returning to normal interactions and behaviour. Here, we consider the optimal targeting of vaccination within the UK, with the aim of minimising future deaths or quality adjusted life year (QALY) losses. We show that, for a range of assumptions on the action and efficacy of the vaccine, targeting older age groups first is optimal and can avoid a second wave if the vaccine prevents transmission as well as disease.

X-ray phase-contrast topography to measure the surface stress and bulk strain in a silicon crystal

The measurement of the Si lattice parameter by X-ray interferometry assumes the use of strain-free crystals, which might not be true because of intrinsic stresses due to surface relaxation, reconstruction and oxidation. X-ray phase-contrast topography was used to investigate the strain sensitivity to the finishing, annealing and coating of interferometer crystals. The topography capabilities were assessed by measuring the lattice strain due to films of copper deposited on the interferometer mirror crystal. A by-product has been the measurement of the surface stresses after complete relaxation of the coatings.

A Comparative Study of Intramuscular Alfaxalone- or Ketamine-Based Anesthetic Mixtures in Gray Squirrels Undergoing Gonadectomy: Clinical and Physiologic Findings

The gray squirrel is one of the most common invasive species in Europe, whose presence is dangerous for the survival of the European red squirrel. To cope with this biological invasion and to safeguard biodiversity, the LIFE+U-SAVEREDS project aims to protect the red squirrel, by limiting the growth of the current population of gray squirrels and simultaneously promoting their eradication with surgical sterilization. This study compares two different anesthetic protocols, including dexmedetomidine (40 µg/kg) and midazolam (0.3 mg/kg) associated with ketamine (15 mg/kg; n = 25 squirrels) or alfaxalone (5 mg/kg; n = 22 squirrels). A blinded investigator evaluated the quality and onset of sedation, intraoperative anesthesia, and recovery, as well as the physiologic parameters for each animal. Alfaxalone provided a good quality of anesthesia with limited cardiovascular effects (p < 0.05) and good intraoperative myorelaxation. Ketamine induced complete relaxation in a shorter time (p < 0.05) and a rapid (p < 0.001) and excellent (p < 0.05) recovery. Despite the overall superiority of ketamine, alfaxalone appeared to be an adequate alternative anesthetic drug that can be administered without requiring intravascular access. It should be rapidly metabolized and excreted; however, it requires the combination of longer acting sedatives/myorelaxants to prevent a poor recovery quality.

Epsilon iron as a spin-smectic state

Using X-ray emission spectroscopy, we find appreciable local magnetic moments until 30 GPa to 40 GPa in the high-pressure phase of iron; however, no magnetic order is detected with neutron powder diffraction down to 1.8 K, contrary to previous predictions. Our first-principles calculations reveal a “spin-smectic” state lower in energy than previous results. This state forms antiferromagnetic bilayers separated by null spin bilayers, which allows a complete relaxation of the inherent frustration of antiferromagnetism on a hexagonal close-packed lattice. The magnetic bilayers are likely orientationally disordered, owing to the soft interlayer excitations and the near-degeneracy with other smectic phases. This possible lack of long-range correlation agrees with the null results from neutron powder diffraction. An orientationally disordered, spin-smectic state resolves previously perceived contradictions in high-pressure iron and could be integral to explaining its puzzling superconductivity.

Fluorescence yields for doubly excited 2s3s configuration in He-like ions

The wavelengths and rates of single- and double-electron transitions leading to the emission of a single photon between 2s3s and nsn′p (n = 1, 2 and n′ = 2–4) groups in He-like ions with empty K shell have been studied for 15 ions in the range 13 ≤ Z ≤ 54 using fully relativistic multi-configuration Dirac–Fock wavefunctions in the active space approximation. The complete relaxation of atomic orbitals and most important configuration interaction effects have been taken into account. The variations in the admixture of the correlation functions coupled with Breit interaction responsible for the sudden changes in the line intensities of certain transitions from 2s3s have been discussed in detail. The radiative rates of the electric dipole transitions have been evaluated as accurately as possible by taking into account all the non-negligible contributions to the X-ray rates. The Auger rates have been calculated using a scaling procedure on the already existing relativistic radial matrix elements for an initial K hole atom. The present results are compared with other available theoretical data. The computed data can be conveniently used in the analysis of experimental spectra and in the measurements of X-ray fluorescence yields for the doubly excited states under study.

Dynamic characterization of structural relaxation in V2O5–P2O5 bulk oxide glass

The characteristic changes and the complete relaxation process of V2O5–P2O5 oxide glass are studied by dynamic thermal-mechanical analysis and differential scanning calorimetry.

INFLUENCE OF BABBIT RHEOLOGICAL PROPERTY UPON STRESSES IN ANTIFRICTION LAYER OF SLIDER BEARING

The procedure for tests of contact creep in ring bearing-samples is developed and also a generalized diagram of residual stresses formation after babbitting and machining a babbit layer in bearings is obtained. It is shown that the existence of a cyclic deformation of an antifriction layer results in a complete relaxation of the sum of all constant constituents of residual stresses. It is concluded that the main reason of the dissi-pation of strength characteristics in babbit samples consists in rheological properties of this material.

A novel approach to ductal spasm during percutaneous device occlusion of patent ductus arteriosus

Ductal spasm is a rare yet important complication of device occlusions of patent ductus arteriosus. Spasm may result in failure of the procedure, under-sizing of the device, or embolisation of the implanted device as the spasm resolves after the procedure. We describe a novel protocol that rapidly and completely reversed the spasm in eight prematurely born infants who experienced ductal spasm during cardiac catheterisations for patent ductus arteriosus occlusion.In total, eight infants born between 25 and 34 weeks of gestation presented for transcatheter patent ductus arteriosus occlusion between 13 and 87 months of age. All eight patients experienced ductal spasm either immediately before, during, or soon after induction of anaesthesia or only after entering the ductus arteriosus with a catheter. After detection of the spasm, the anaesthetist, in each case, changed the mode of anaesthesia from inhaled sevoflurane to total intravenous anaesthesia with propofol, reduced the inhaled oxygen fraction to 21%, and initiated a continuous intravenous infusion of prostaglandin E1.The first two steps (total intravenous anaesthesia and FiO2 0.21) resulted in only partial relaxation of the spasm. Complete relaxation was attained after intravenous prostaglandin E1 infusions of only 10–15 minutes’ duration. While maintaining this protocol, six ducti were successfully occluded and two were considered to be unsuitable for device occlusion and were referred for surgery.Ductal spasm during transcatheter occlusion may be reliably resolved and the procedure safely completed by a simple anaesthetic protocol, including the continuous infusion of intravenous prostaglandin E1.