Nanomaterials by severe plastic deformation: review of historical developments and recent advances

International audienceSevere plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity

Ideal MHD flow behind interplanetary shocks driven by magnetic clouds

We present an ideal MHD theory to describe for the first time the “magnetic barrier” (or “depletion layer”) of that class of interplanetary ejecta called magnetic clouds. By “magnetic barrier” we mean that region of the sheath where the magnetic pressure is comparable to, or larger than, the gas pressure and where, therefore, the effects of the magnetic field on the flow are substantial. We model magnetic clouds as cylindrical flux ropes. We consider three cases: one steady state and two nonsteady situations. The two nonsteady situations correspond to (1) a self-similarly expanding magnetic cloud, and (2) to a nonexpanding magnetic cloud which has a net bulk motion with respect to the medium at infinity. In all cases the cloud drives an interplanetary shock ahead of it. We describe an algorithm to integrate the MHD equations in which the behavior of the sum of the magnetic and plasma pressure is prescribed. We assume here that the sum of the magnetic and plasma pressure is constant along any line normal to the magnetic cloud boundary. We find that in steady state the cloud boundary cannot be a tangential discontinuity, that is, a finite magnetic barrier thickness can only be obtained with a reconnecting cloud boundary. In general, the magnetic barriers of magnetic clouds are thick, that is, they are a substantial fraction of the cloud\u27s sheath. In steady state and the nonsteady case (situation 2, above), their width depends inversely on the Alfvén Mach number. The non-steady state (situation 1) has similarities with the problem of solar wind flow around the terrestrial magnetosphere. In particular, the barrier thickness in this case is proportional to the inverse square of the Alfvén Mach number. This work should be useful in the interpretation of data from the sheath region ahead of magnetic clouds driving interplanetary shocks

Magnetosheath parameters and reconnection: a case study for the near-cusp region and the equatorial flank

We use the magnetohydrodynamic approach to calculate all plasma and magnetic field quantities along a line normal to the magnetopause, beginning at the bow shock, through the magnetosheath and magnetopause, and into the magnetosphere. Our method is based on a perturbation calculation, where we expand in orders of , with MA∞ the Alfvén Mach number upstream of the bow shock. The calculations are carried out (1) in the noon-midnight meridian at latitudes just south of the northern cusp, and (2) in the equatorial flank region. Our calculations are for an interplanetary magnetic field (IMF) which is directed perpendicular to the upstream solar wind. We consider two orientations of the IMF. In one case, the interplanetary field points due south, i.e. antiparallel to the magnetospheric field in the subsolar point. In the second case, it lies in the equatorial plane and points from dusk to dawn. For each of these different orientations of the IMF, in situ observations of reconnection have been made. In the magnetosheath region adjacent to the magnetopause, i.e. in the so-called magnetic barrier, the magnetic forces react back on the plasma flow. This effect is included consistently in the calculation by the use of a special coordinate system. The magnetic field tension accelerates the plasma in a direction perpendicular to the field and thus the magnetic field produces an asymmetry in the flow field. At the magnetopause we describe shock-type reconnection, taking as input on the magnetosheath side the results of the above calculation and taking at the magnetospheric side typical values for the outer boundary of the magnetosphere. The format in which the results are presented is similar to that used in the presentation of bulk parameters and magnetic field measurements obtained from spacecraft

Decreased Cerebrospinal Fluid Antioxidative Capacity Is Related to Disease Severity and Progression in Early Multiple Sclerosis

Background: Oxidative stress-induced neuronal damage in multiple sclerosis (MS) results from an imbalance between toxic free radicals and counteracting antioxidants, i.e., antioxidative capacity (AOC). The relation of AOC to outcome measures in MS still remains inconclusive. We aimed to compare AOC in cerebrospinal fluid (CSF) and serum between early MS and controls and assess its correlation with clinical/radiological measures. Methods: We determined AOC (ability of CSF and serum of patients to inhibit 2,2′-azobis(2-amidinopropane) dihydrochloride-induced oxidation of dihydrorhodamine) in clinically isolated syndrome (CIS)/early relapsing-remitting MS (RRMS) (n = 55/11) and non-inflammatory neurological controls (n = 67). MS patients underwent clinical follow-up (median, 4.5; IQR, 5.2 years) and brain MRI at 3 T (baseline/follow-up n = 47/34; median time interval, 3.5; IQR, 2.1 years) to determine subclinical disease activity. Results: CSF AOC was differently regulated among CIS, RRMS and controls (p = 0.031) and lower in RRMS vs. CIS (p = 0.020). Lower CSF AOC correlated with physical disability (r = −0.365, p = 0.004) and risk for future relapses (exp(β) = 0.929, p = 0.033). No correlations with MRI metrics were found. Conclusion: Decreased CSF AOC was associated with increased disability and clinical disease activity in MS. While our finding cannot prove causation, they should prompt further investigations into the role of AOC in the evolution of MS

Use of ECG and Other Simple Non-Invasive Tools to Assess Pulmonary Hypertension - Fig 4

<p><b>A-D.</b> Associations between the simple non-invasive parameters and mean pulmonary arterial pressure–data based on the analysis of the prospective cohort. The red dot represents the patient with pulmonary hypertension who was missed by the algorithm. (mPAP: mean pulmonary arterial pressure, NTproBNP: N-terminal pro brain natriuretic peptide, art SO2: arterial oxygen saturation).</p

Algorithm to identify and to exclude pulmonary hypertension by simple non-invasive tools–data based on the analysis of the prospective cohort.

<p>(RAD: right axis deviation, PAP: mean pulmonary arterial pressure, WHO: WHO functional class, NTproBNP: N-terminal pro brain natriuretic peptide, art SO2: arterial oxygen saturation).</p