Finite element computation of transient dissipative double diffusive magneto-convective nanofluid flow from a rotating vertical porous surface in porous media

This paper aimed to investigate the transient dissipative MHD double diffusive free convective boundary layer flow of electrically-conducting nanofluids from a stationary or moving vertical porous surface in a rotating high permeability porous medium, considering buoyancy, thermal radiation and first order chemical reaction. Thermo-diffusion (Soret) and diffuso-thermal (Dufour) effects are also considered. Darcy’s law is employed. The mathematical model is formulated by considering water-based nanofluids containing metallic nano-particles for both stationary and moving plate cases. Three nanofluids are examined, namely copper, aluminium oxide or titanium oxide in water. The transformed non-linear, coupled, dimensionless partial differential equations describing the flow are solved with physically appropriate boundary conditions by using Galerkin weighted residual scheme. For prescribed permeability, numerical results are presented graphically for the influence of a number of emerging parameters. Validation of finite element solutions for skin friction and Nusselt number is achieved via comparison with the previously published work as special cases of the present investigation and very good correlation obtained. Increasing rotational parameter is observed to reduce both primary and secondary velocity components. Primary and secondary velocities are consistently elevated with increasing Soret, Dufour, thermal Grashof and solutal Grashof numbers. Increasing Schmidt number, chemical reaction and suction parameter both suppress nano - particle concentration whereas the converse behavior is computed with increasing Soret number. The study is relevant to high temperature rotating chemical engineering systems exploiting magnetized nanofluids and also electromagnetic nanomaterial manufacturing processes

Standardisation of magnetic nanoparticles in liquid suspension

Suspensions of magnetic nanoparticles offer diverse opportunities for technology innovation, spanning a large number of industry sectors from imaging and actuation based applications in biomedicine and biotechnology, through large-scale environmental remediation uses such as water purification, to engineering-based applications such as position-controlled lubricants and soaps. Continuous advances in their manufacture have produced an ever-growing range of products, each with their own unique properties. At the same time, the characterisation of magnetic nanoparticles is often complex, and expert knowledge is needed to correctly interpret the measurement data. In many cases, the stringent requirements of the end-user technologies dictate that magnetic nanoparticle products should be clearly defined, well characterised, consistent and safe; or to put it another way—standardised. The aims of this document are to outline the concepts and terminology necessary for discussion of magnetic nanoparticles, to examine the current state-of-the-art in characterisation methods necessary for the most prominent applications of magnetic nanoparticle suspensions, to suggest a possible structure for the future development of standardisation within the field, and to identify areas and topics which deserve to be the focus of future work items. We discuss potential roadmaps for the future standardisation of this developing industry, and the likely challenges to be encountered along the way

Do macromolecular and spline baselines affect the metabolite quantification at 9.4T?

Purpose/Introduction: One of the major goals in order to make MRSpectroscopy relevant for clinical practice is to ensure a robust quantitation of the spectra. Several previous studies investigated the influence of the macromolecular baseline(MMB) on the spectral quantification accuracy and precision1–12. This work extends previous work by investigating the influence of (1) the brain region specificity of the macromolecular baseline model and (2) the parameters of the additional spline-baseline on the quantification accuracy of spectra measured in the human brain at 9.4T. Subjects and Methods: Metabolite-cycled semiLASER (MCsLASER) 13 spectra (TR = 6000 ms/TE = 24 ms) were acquired from 8 volunteers(aged 28 ± 3) at a 9.4T Siemens Magnetom scanner from the occipital lobe(Occ.) with a mixed grey(40) and white matter(56) content, and from the left parietal lobe (lPar.) with a high white matter content(80). MMB models were created from data acquired using a double inversion MCsLASER sequence(-TI1 = 2360 ms/TI2 = 625 ms)14 from both regions (Fig. 1). using either of the two different MMB models to fit spectra from both brain regions; (2) varying parameters of the spline-baseline stiffness. The paired Wilcoxon test was used to find statistically significant differences in metabolite concentrations. Results: Up to 16 metabolites were readily quantified for both regions with Cramer Rao Lower Bounds of less than 20. The changes in concentrations for quantifying the spectra using the MMB from the corresponding region, versus using the MMB from the other region showed no significant difference (Fig. 2). The parameter settings for the spline-baseline did not influence this result. A-B show the fitted metabolite concentrations and their standard deviations for the different subjects, comparing the use of the different MMB for the fitting of the left parietal and the occipital lobe respectively (dkntmn = 1). The lowest measured p-value for a metabolite concentration change upon changing the MMB was 0.093 (not corrected for multiple comparisons). C-D show sample fit results for using the different MMBs for a left parietal spectrum. However, changes in the stiffness of the fitted spline-baseline lead to statistically significant concentration differences for multiple metabolites between stiff and more flexible spline-baselines (Fig. 3). Already moderately flexible spline-baselines (dkntmn\0.5) influence the accuracy and precision of concentration estimates for several metabolites. A–B show the fitted metabolite concentrations and their standard deviations for the different subjects, comparing the use of the different stiffness parameters of the spline baseline for the fitting (the region specific MMB was used). The red stars indicate metabolite concentration pairs for which a significant change in concentrations was observed (p-value\0.05, not corrected for multiple comparisons). C-D show sample fit results for using the different spline baseline stiffness values for an occipital spectrum. Discussion/Conclusion: This work shows for the first time, that using MMBs from different locations (lPar. and Occ.), with different underlying tissue composition does not lead to significant changes in the fitting results of the metabolites at 9.4T human studies. However, it was found, that the stiffness of the additional spline-baseline fit can significantly influence the metabolite concentrations, hence the flexibility of the spline-baseline should be restricted when quantifying spectra

Different worlds of contention? Protest in Northwestern, Southern and Eastern Europe

Despite the voluminous literature on the ‘normalisation of protest’, the protest arena is seen as a bastion of left‐wing mobilisation. While citizens on the left readily turn to the streets, citizens on the right only settle for it as a ‘second best option’. However, most studies are based on aggregated cross‐national comparisons or only include Northwestern Europe. We contend the aggregate‐level perspective hides different dynamics of protest across Europe. Based on individual‐level data from the European Social Survey (2002–2016), we investigate the relationship between ideology and protest as a key component of the normalisation of protest. Using hierarchical logistic regression models, we show that while protest is becoming more common, citizens with different ideological views are not equal in their protest participation across the three European regions. Instead of a general left predominance, we find that in Eastern European countries, right‐wing citizens are more likely to protest than those on the left. In Northwestern and Southern European countries, we find the reverse relationship, left‐wing citizens are more likely to protest than their right‐wing counterparts. Lessons drawn from the protest experience in Northwestern Europe characterised by historical mobilisation by the New Left are of limited use for explaining the ideological composition of protest in the Southern and Eastern European countries. We identify historical and contemporary regime access as the mechanism underlying regional patterns: citizens with ideological views that were historically in opposition are more likely to protest. In terms of contemporary regime access, we find that partisanship enhances the effect of ideology, while ideological distance from the government has a different effect in the three regions. As protest gains in importance as a form of participation, the paper contributes to our understanding of regional divergence in the extent to which citizens with varying ideological views use this tool

Fitting comparison for 9.4T 1D semi-LASER and 2D-J-resolved semi-LASER data

In this abstract, we present an adapted version of the ProFit-V2 fitting software to fit J-resolved semi-LASER data at 9.4T. Simulated basis sets with ideal pulses show the need to reduce the echo time to account for the spin locking effect of the adiabatic pulses. Further, a comparison of the fitting error estimations using correlation matrices and Cramer-Rao Lower Bounds with a metabolite cycled semi-LASER fitted with LCModel is done

Qualitative Comparison between In Vivo J-Resolved Semi-LASER at 3 T and 9.4 T

J-resolved semi-LASER with maximum-echo sampling is optimized at 9.4T and compared with the same implementation at 3T in terms of SNR and spectral resolution. SODA scheme is appreciated for the sequence rather than the MC scheme. SNR at 9.4T (t1 steps: 85) was approximately 5.8 times greater than at 3T (t1 steps: 100) and strongly coupled peaks are well-resolved. However, the trade-off between SNR and spectral resolution is explained as lactate (1.32 ppm), a weakly-coupled metabolite, is better resolved at 3T. Higher band-width AFP pulses helped in almost vanishing the J-refocused peaks which made the J-resolved peaks clearly distinguishable. A few interesting downfield peaks and the doublet of NAA (7.82ppm) are observed