Correction to: Impact of leg bending in the patient-specific computational fluid dynamics of popliteal stenting

Acta Mechanica Sinica - A Correction to this paper has been published: https://doi.org/10.1007/s10409-021-01066-2     

Molecular dynamics of liquid acetone determined by depolarized Rayleigh and low-frequency Raman scattering spectroscopy

Slow to ultrafast dynamics of liquid acetone at variable temperature was investigated by depolarized Rayleigh and low-frequency Raman scattering spectroscopy, in the region 0-200 cm(-1). A detailed analysis was performed on the spectra and corresponding time responses, and a consistent view of the molecular dynamics of this dipolar solvent was obtained. The effects of temperature on the spectra were interpreted, and distinct dynamical processes identified. At very low frequencies, or long time scales, acetone dynamics is characterized by a slow diffusive reorientation obeying the Stokes-Einstein-Debye hydrodynamic theory only in the limit of subslip boundary conditions. An alternative model based on the microviscosity concept proved to be able to reproduce this correlation time and its temperature dependence. A comparative analysis of collective and single-molecule reorientational times, these latter estimated from intramolecular Raman spectra, led to an orientational correlation parameter g(2) of unity, which denotes a statistical disorder of molecular polarizability tensors. A fast local restructuring process is putatively responsible for an additional contribution at subpicosecond time scales often referred to as intermediate response in other molecular liquids. The high frequency portion of the dynamical susceptibility showed the signature of librational intermolecular motions, giving rise to an ultrafast decay of the time correlation function of polarizability anisotropy. The overall approach, which provided valuable information on dynamics, structure and molecular interactions of neat acetone, will be applied to acetone electrolytic solutions.     

Comparison of hydrogen bonding in 1-octanol and 2-octanol as probed by spectroscopic techniques

Liquid 1-octanol and 2-octanol have been investigated by infrared (IR), Raman, and Brillouin experiments in the 10-90 degrees C temperature range. Self-association properties of the neat liquids are described in terms of a three-state model in which OH oscillators differently implicated in the formation of H-bonds are considered. The results are in quantitative agreement with recent computational studies for 1-octanol. The H-bond probability is obtained by Raman data, and a stochastic model of H-bonded chains gives a consistent picture of the self-association characteristics. Average values of hydrogen bond enthalpy and entropy are evaluated. The H-bond formation enthalpy is ca. -22 kJ/mol and is slightly dependent on the structural isomerism. The different degree of self-association for the two octanols is attributed to entropic factors. The more shielded 2-isomer forms larger fractions of smaller, less cooperative, and more ordered clusters, likely corresponding to cyclic structures. Signatures of a different cluster organization are also evidenced by comparing the H-bond energy dispersion (HBED) of OH stretching IR bands. A limiting cooperative H-bond enthalpy value of 27 kJ/mol is found. It is also proposed that the different H-bonding capabilities may modulate the extent of interaggregate hydrocarbon interactions, which is important in explaining the differences in molar volume, compressibility, and vaporization enthalpy for the two isomers.     

Evidence that absorption in the π+ π− π− system in nuclear matter is stronger in the JP = 0− than in the JP = 1+ state

In the reaction π^? + A → π⁺π^?π^? + A at 15.1 GeV/c the coherently produced 3π mass spectrum has a broad peak around 1.1 GeV which consists mainly of a J^P = 1⁺ state and of a smaller fraction of 0^-. Comparing the observed dependence of the production of these diffractive states on the atomic weight A of the target nuclei with the optical model, we have studied the absorption of the produced states in nuclear matter. We have found the following values of the absorption cross-sections: σ₂(0^-) = 49_?7⁺⁹ mb and σ₂(1⁺) = 15.8_?1.3^+1.5 mb.     

Semicoherent elastic pion-carbon scattering at 25 and 40 GeV/c

In the frame of a systematic study of hadron-nucleus interactions performed at the Serpukhov accelerator (CERN-IHEP 5th experiment), semicoherent elastic scattering on carbon $\text{π}{}^{\mathrm{?12}}\text{C}\text{a}\text{?}\text{π}{}^{\mathrm{?12}}\text{C}{}^1\text{(4.44}\text{MeV}\text{)}$ was investigated with 25 and 40 GeV/c incident pions.The experimental data were obtained with a counter technique, looking at the coincidence between the scattered pion and the 4.44 MeV photon from the J^P = 2⁺ carbon excited state detected by a NaI counter.The value obtained for the integrated cross section at 40 GeV/c in the 0.0032 ? |t| ? 0.27 (GeV/c)² four-momentum transfer range isσ = 1.16 ± 0.11 mb.According to the theoretical models, this t-range at 40 GeV/c covers more than 99% of the angular distribution, so the above value almost corresponds to the total semicoherent elastic cross section.     

Spatio-temporal anomalous diffusion in heterogeneous media by nuclear magnetic resonance

In this paper, we describe nuclear magnetic resonance measurements of water diffusion in highly confined and heterogeneous colloidal systems using an anomalous diffusion model. For the first time, temporal and spatial fractional exponents, α and μ, introduced within the framework of continuous time random walk, are simultaneously measured by pulsed gradient spin-echo NMR technique in samples of micro-beads dispersed in aqueous solution. In order to mimic media with low and high level of disorder, mono-dispersed and poly-dispersed samples are used. We find that the exponent α depends on the disorder degree of the system. Conversely, the exponent μ depends on both bead sizes and magnetic susceptibility differences within samples. The new procedure proposed here may be a useful tool to probe porous materials and microstructural features of biological tissue.     

Structure Analysis of Solid Lipid Nanoparticles for Drug Delivery: A Combined USANS/SANS Study

Suspensions of solid lipid nanoparticles (SLNs) stabilized with emulsifiers have been extensively investigated (since the 1990s) as drug carriers, although details of their ultrastructure are poorly defined. Previously, a novel microwave‐assisted microemulsion‐based technique to prepare SLNs was reported. To understand the detailed internal structure of these SLNs, ultra‐small angle neutron scattering (USANS) and small angle neutron scattering (SANS) experiments are conducted on suspensions of hydrogenated stearic acid SLNs stabilized with hydrogenated Tween 20 surfactant in D₂O. Together, SANS and USANS gives a combined Q range of 0.000047 to 0.6 Å^?1 (corresponding to a size range of ≈1 nm–15 µm). This extended Q range allows a comprehensive understanding of the hierarchical structure of SLNs. The data are consistent with the multi‐length scale structure of SLNs having polydispersed large particles with roughened surfaces at the microscale level. At the nanoscale level, the results are consistent with the SLNs having an ellipsoidal shape intermediate between spheres and rods, with a crossover from mass fractals to surface fractals. The elucidation of this structure is particularly important given that the structure influences the stability and drug release properties of the nanoparticles. These results assist in the development of systems with desired shape and properties.     

Biodegradation of sequentially surface treated lignocellulose reinforced polylactic acid composites: Carbon dioxide evolution and morphology

Maple fibres were treated with a variety of sequential treatments, namely sodium hydroxide (NaOH), NaOH followed by acetylation, or NaOH followed by silanation. These fibres were incorporated into a polylactic acid (PLA) composite and the biodegradation effects were investigated. After 124 days, all composites had exceeded 90% biodegradation with most close to 100%. The PLA composite with the NaOH-treated fibres had the quickest onset of degradation (4.9 days) and highest peak rate of degradation (1.77% biodegradation/day) of all composites studied. Neat PLA had a similarly high peak rate of degradation at 1.85% biodegradation/day, but had a later onset of 11 days. Gel permeation chromatography (GPC) analysis showed the earlier onset of degradation of the composites was caused by increased hydrolysis during composite fabrication as well as composting. GPC showed the formation of up to three molecular weight bands in the PLA during composting which were hypothesised to be occurring by surface hydrolysis, bulk hydrolysis and hydrolysis at the fibre interface. Analysing the remaining composite revealed the NaOH treatment not only caused an increased rate of degradation in the PLA through increase fibre porosity, but also caused an increased rate of degradation in the fibre from the lack of surface waxes and hemicellulose. Similar, yet slower, behaviours were also seen in the NaOH followed by acetylation and NaOH followed by silane treated composites with all composites degrading more rapidly than the neat PLA and neat maple fibre samples.