Finding the bulk viscosity of air from Rayleigh-Brillouin light scattering spectra.

Spectral line shape models can successfully reproduce experimental Rayleigh-Brillouin spectra, but they need knowledge about the bulk viscosity ηb. Light scattering involves GHz frequencies, but since ηb is only documented at low frequencies, ηb is usually left as a free parameter, which is determined by a fit of the model to an experimental spectrum. The question is whether models work so well because of this freedom. Moreover, for light scattering in air, spectral models view "air" as an effective molecule. We critically evaluate the use of ηb as a fit parameter by comparing ηb obtained from fits of the Tenti S6 model to the result of Direct Simulation Monte Carlo (DSMC) for a mixture of Nitrogen and Oxygen. These simulations are used to compute light scattering spectra, which are then compared to experiments. The DSMC simulation parameters are cross-checked with a molecular dynamics simulation based on intermolecular potentials. At large values of the uniformity parameter y, y ≈ 4, where the Brillouin contribution to spectra is large, fitted ηb are 20% larger than the ones from DSMC, while the quality of the simulated spectra is comparable to that of the Tenti S6 line shape model. At smaller y, the difference between fitted and simulated ηb can be as large as 100%. We hypothesize the breakdown of the bulk viscosity concept to be the cause of this fallacy.

Relaxation of rotational-vibrational energy and volume viscosity in H-H2 mixtures.

We investigate a kinetic model for H-H2 mixtures in a regime where translational/rotational and vibrational-resonant energy exchanges are fast whereas vibrational energy variations are slow. In a relaxation regime, the effective volume viscosity is found to involve contributions from the rotational volume viscosity, the vibrational volume viscosity, the relaxation pressure, and the perturbed source term. In the thermodynamic equilibrium limit, the sum of these four terms converges toward the one-temperature two-mode volume viscosity. The theoretical results are applied to the calculation of the volume viscosities of molecular hydrogen in the trace limit on the basis of a complete set of state-selected cross sections for the H + H2(v, j) system.

Lateral Gradual Opening Osteotomy of the Tibia With Monolateral External Fixator for Correcting the Valgus Deformity of the Tibia.

The valgus deformity in the tibia requires correction because it places increased pressure on the lateral compartment of the knee, intensifying the degenerative process. Correction strategies are diverse and depend on patient profile, age, and soft-tissue conditions as well as the orthopaedic surgeon's experience with different surgical materials. Deformity size and location are the primary factors contributing to material and shape choice, whether gradual or acute. The only gradual correction approach involves the use of a monolateral or circular external fixator. This is the only indication for correction in cases of excellent deformity, soft-tissue involvement, and a history of bone infection. This study aimed to present a gradual correction technique for tibial valgus deformity using a monolateral external fixator as well as its postoperative follow-up. This technique has the advantages of greater patient acceptance, lighter assembly, and briefer distraction owing to the use of a single piece as well as the ability of the operated limb to bear a load the day after the surgical procedure and dynamic outpatient follow-up.

Molecular simulation of Rayleigh-Brillouin scattering in binary gas mixtures and extraction of the rotational relaxation numbers.

Rayleigh-Brillouin scattering (RBS) in gases has received considerable attention due to its applications in LIDAR (light detection and ranging) remote sensing and gas property measurements. In most cases, the RBS spectra in the kinetic regime are calculated based on kinetic model equations, which are difficult to be applied to complex gas mixtures. In this work, we employ two widely used molecular simulation methods, i.e., direct simulation Monte Carlo (DSMC) and molecular dynamics (MD), to calculate the spontaneous RBS spectra of binary gas mixtures. We validate these two methods by comparing the simulation results for mixtures of argon and helium with the experimental results. Then we extend the RBS calculations to gas mixtures involving polyatomic gases. The rotational relaxation numbers specific to each species pair in DSMC are determined by fitting the DSMC spectra to the MD spectra. Our results show that all the rotational relaxation numbers for air composed of N_{2} and O_{2} increase with temperature in the range of 300-750 K. We further calculate the RBS spectra for binary mixtures composed of N_{2} and one noble monatomic gas, and the simulation results show that the rotational relaxation of N_{2} is greatly affected by the mass of the noble gas atoms. This work demonstrates that RBS is a promising and alternative way to study the rotational relaxation process in gas mixtures.

Human adventitial pericytes provide a unique source of anti-calcific cells for cardiac valve engineering: Role of microRNA-132-3p.

AIMS: Tissue engineering aims to improve the longevity of prosthetic heart valves. However, the optimal cell source has yet to be determined. This study aimed to establish a mechanistic rationale supporting the suitability of human adventitial pericytes (APCs). METHODS AND RESULTS: APCs were immunomagnetically sorted from saphenous vein leftovers of patients undergoing coronary artery bypass graft surgery and antigenically characterized for purity. Unlike bone marrow-derived mesenchymal stromal cells (BM-MSCs), APCs were resistant to calcification and delayed osteochondrogenic differentiation upon high phosphate (HP) induction, as assessed by cytochemistry and expression of osteogenic markers. Moreover, glycolysis was activated during osteogenic differentiation of BM-MSCs, whereas APCs showed no increase in glycolysis upon HP challenge. The microRNA-132-3p (miR-132), a known inhibitor of osteogenesis, was found constitutively expressed by APCs and upregulated following HP stimulation. The anti-calcific role of miR-132 was further corroborated by in silico analysis, luciferase assays in HEK293 cells, and transfecting APCs with miR-132 agomir and antagomir, followed by assessment of osteochondrogenic markers. Interestingly, treatment of swine cardiac valves with APC-derived conditioned medium conferred them with resistance to HP-induced osteogenesis, with this effect being negated when using the medium of miR-132-silenced APCs. Additionally, as an initial bioengineering step, APCs were successfully engrafted onto pericardium sheets, where they proliferated and promoted aortic endothelial cells attraction, a process mimicking valve endothelialization. CONCLUSIONS: Human APCs are resistant to calcification compared with BM-MSCs and convey the anti-calcific phenotype to heart valves through miR-132. These findings may open new important avenues for prosthetic valve cellularization.

Permanent end-colostomy parastomal hernia prevention using a novel three-dimensional mesh.

PURPOSE: Prophylactic mesh placement has been proposed to reduce the high occurrence of parastomal hernia (PSH) after stoma formation. METHODS: This is an observational study comparing two cohorts of patients: a mesh prophylaxis group (who received mesh prevention since introduction at our Institution) and a no mesh prophylaxis group (retrospectively selected from our historical series). Same exclusion criteria were applied for both groups. The study was conducted at a tertiary referral center for colorectal surgery. 43 patients were operated with mesh prophylaxis between May 2015 and may 2019. 45 patients underwent end-colostomy formation without prophylaxis between April 2011 and April 2015. The primary outcome measure was PSH development at 12-month follow up. RESULTS: Demographic variables and risk factors for PSH were comparable between the two groups. There was no difference between the two cohorts in terms of operative time and main early postoperative outcomes. 37 patients completed the 12-month follow up in each group. PSH occurrence after 12-months was 11% in the mesh prophylaxis group and 54% in the no mesh prophylaxis group (p < 0.0001). There were no differences in long-term complications. 5% of patients who received mesh prophylaxis underwent emergency surgery for bowel occlusion at 7 and 10 months after surgery, with partial or complete mesh removal. At multivariate analysis, mesh prophylaxis was a protective factor for PSH development at 12 months (p < 0.0001). CONCLUSIONS: Prophylactic intraperitoneal mesh placement appears to be effective in preventing PSH.

First measurements of optical emission spectroscopy on SPIDER negative ion source.

Optical Emission Spectroscopy (OES) on the SPIDER negative ion source has been collecting data since the beginning of operation in Summer 2018. The first few months were devoted to complete the diagnostic commissioning and its integration with the SPIDER control and data acquisition system. Consistent sets of spectroscopic data have been acquired under different experimental conditions, not only varying the plasma source filling pressure and injected power but also changing the RF generator frequencies and the strength of the magnetic field acting as a filter in front of the plasma grid. The main results of OES data analysis are presented in this work. SPIDER optical emission diagnostic comprises a set of 66 channels wavelength resolved and 36 single line channels by means of interference filtering. Some of them collect the photons along line of sight (LOS) perpendicular to the grids through the 8 RF drivers and others along LOS parallel to and near the grids, both horizontally and vertically. Since the starting of extraction experiments, 22 channels have been dedicated to collect the extracted beam emission. The LOS layout allows tracing two 9-point vertical profiles of the source plasma in the extraction region at 35 and 5 mm from the Plasma Grid (PG) and four 4-point horizontal profiles spanning the 65 mm region before the PG. It is also possible to collect spectra from LOS looking in between the grids. Both Balmer series and Fulcher band between 600 nm and 640 nm were routinely collected. Their intensities are very sensitive to the plasma parameters and when coupled to a collisional radiative model can give an estimation of the electron density and gas dissociation. It has been found that the Balmer emission and gas dissociation inside the drivers scale linearly with the RF power, the latter reaching a value up to 20% at high power and low pressure. Rotational gas temperature has also been evaluated; it ranged between 900 K and 1400 K, where higher values were reached for higher pressures and RF powers.

MicroRNAs as potential biomarkers in congenital heart surgery.

OBJECTIVE: Pediatric congenital heart surgery (CHS) involves intracardiac, valvular, and vascular repairs. Accurate tools to aid short-term outcome prediction in pediatric CHS are lacking. Clinical scores, such as the vasoactive-inotrope score and ventilation index, are used to define outcome in clinical studies. MicroRNA-1-3p (miR-1) is expressed by both cardiomyocytes and vascular cells and is regulated by hypoxia. In adult patients, miR-1 increases in the circulation after open-heart cardiac surgery, suggesting its potential as a clinical biomarker. Thus, we investigated whether perioperative circulating miR-1 measurements can help predict post-CHS short-term outcomes in pediatric patients. METHODS: Plasma miR-1 was retrospectively measured in a cohort of 199 consecutive pediatric CHS patients (median age 1.2 years). Samples were taken before surgery and at the end of the operation. Plasma miR-1 concentration was measured by reverse transcription-quantitative polymerase chain reaction and expressed as miR-1 copies/µL and as relative expression to spiked-in exogenous cel-miR-39. RESULTS: Baseline plasma miR-1 did not vary across different diagnoses, increased during surgery (204-fold median relative increase, P < .001), and was associated with aortic crossclamp duration postoperatively (P < .001). Importantly, miR-1 levels at the end of the operation positively correlated with intensive care stay (P < .001), early severe cardiovascular events (P = .01), and with high vasoactive-inotrope score (P = .001) and ventilation index (P < .001), suggesting that miR-1 could accelerate the identification of patients with cardiopulmonary bypass-related ischemic complications, requiring more intensive support. CONCLUSIONS: Our study suggests miR-1 as a novel potential circulating biomarker to predict early postoperative outcome and inform clinical management in pediatric heart surgery.

Collision integrals for interactions involving atoms in electronically excited states.

Transport collision integrals for low-lying excited states of nitrogen atoms and ions are derived in the framework of a phenomenological approach following, where possible, also the traditional multipotential procedure. The two sets of results are compared considering critically the observed deviations, and finally, the proposed model is validated by comparison with oxygen atom-atom interactions. In addition, an attempt is made to extend the proposed phenomenological method to interactions involving high-lying excited states, taking into account the symmetric interaction of two excited hydrogen atoms, characterized by increasing principal quantum number.

Could left ventricular apical ballooning represent spontaneous myocardial infarction abortion?

Left ventricular apical ballooning, also named tako-tsubo cardiomyopathy, is a syndrome characterized by chest pain, transient left ventricular dysfunction and specific electrocardiographic changes mimicking an acute myocardial infarction without significant stenosis on the coronary angiogram. Although the aetiology remains unknown, several reports have found that preceding psychological stress could act as a trigger. This report describes a case of tako-tsubo-like left ventricular apical ballooning in a patient with "soft" atherosclerotic plaque at the middle portion of the left anterior descending coronary artery.