Noninvasive Assessment of Fractional Flow Reserve Using Mathematical Modeling of Coronary Flow.

Nowadays an invasive evaluation of fractional flow reserve (FFR) is one of the main methods used for detecting lesions that cause ischemia. Invasively obtained FFR <0.75 has the specificity of 100 %, and FFR >0.80 has the sensitivity >90 %. Recent achievements in computational fluid dynamics and computer simulations allow noninvasive assessment of FFR using data obtained by CT angiography performed according to standard protocol at rest without additional radiation, modification of image acquisition protocols, or added medications for vasodilatation. The present review covers the results of the DISCOVER, the NXT, the DEFACTO and the PLATFORM randomized multicenter studies as well as the prospects of using a noninvasive method for measuring FFR developed by specialists of the Institute of Numerical Mathematics in collaboration with specialists of the I. M. Sechenov First Moscow State Medical University.

[Asymptomatic atherosclerosis of the brachiocephalic arteries: Current approaches to diagnosis and treatment]. / Bessimptomnyi ateroskleroz brakhiotsefal'nykh arterii - sovremennye podkhody k diagnostike i lecheniiu.

Acute cerebrovascular accident (ACVA) and transient ischemic attack are among the leading causes of morbidity, disability, and mortality in the Russian Federation and the world. Ischemic strokes account for 70-80% of all ACVAs, with 20-30% of them being associated with stenotic atherosclerosis of the brachiocephalic arteries (BCA). The paper describes modern views on the problem of asymptomatic BCA atherosclerosis and considers the possibilities of identifying risk groups among the patients with asymptomatic atherosclerosis of the BCA.

Evaluation of Hemodynamic Significance of Stenosis in Multiple Involvement of the Coronary Vessels by Mathematical Simulation.

We use a mathematical model of one-dimensional blood flow in a network of blood vessels for in silico evaluation of hemodynamic significance of stenoses in multivessel coronary disease. Two cases were addressed: two stenosed vessels with different diameters and with the same degree of occlusion and two consecutive stenoses in the same vessel. We show that two criteria for the evaluation of hemodynamic significance based on the degree of stenosis and based on fractional flow reserve can give contradictory indications for surgical intervention. We also show that fractional flow reserve computation originally proposed for a single stenosis should be modified in the case of multivessel stenotic disease.

[Role of measurement of fractional flow reserve in coronary artery atherosclerosis].

The paper considers coronary flow in health and coronary flow autoregulation in health and disease. It gives basic methods used to estimate coronary flow reserve in patients with coronary atherosclerosis. The physiological bases for determining fractional flow reserve are presented. Clinical trials investigating the use of fractional flow reserve in patients with coronary heart disease are analyzed.

Positron annihilation spectroscopy study of radiation-induced defects in W and Fe irradiated with neutrons with different spectra.

The paper presents new knowledge on primary defect formation in tungsten (W) and iron (Fe) irradiated by fission and high-energy neutrons at near-room temperature. Using a well-established method of positron-annihilation lifetime-spectroscopy (PALS), it was found that irradiation of W in the fission reactor and by high-energy neutrons from the p(35 MeV)-Be generator leads to the formation of small radiation-induced vacancy clusters with comparable mean size. In the case of Fe, smaller mean size of primary radiation-induced vacancy clusters was measured after irradiation with fission neutrons compared to irradiation with high-energy neutrons from the p(35 MeV)-Be generator. It was found that one of the reasons of the formation of the larger size of the defects with lower density in Fe is lower flux in the case of irradiation with high-energy neutrons from the p(35 MeV)-Be source. The second reason is enhanced defect agglomeration and recombination within the energetic displacement cascade at high energy primary knock-on-atoms (PKAs). This is consistent with the concept of the athermal recombination corrected (arc-dpa) model, although the measured dpa cross-section of both fission neutrons and wide-spectrum high-energy neutrons in W is between the conventional Norgett-Robinson-Torrens (NRT-dpa) and arc-dpa predictions. This means that the physics of the primary radiation effects in materials is still not fully known and requires further study through a combination of modeling and experimental efforts. The present data serve as a basis for the development of an improved concept of the displacement process.

Analysis of computational problems expressing the overall uncertainties: photons, neutrons and electrons.

In the frame of the EU Coordination Action CONRAD (coordinated network for radiation dosimetry), WP4 was dedicated to work on computational dosimetry with an action entitled 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Participants attempted one or more of eight problems. This paper presents the results from problems 4-8-dealing with the overall uncertainty budget estimate; a short overview of each problem is presented together with a discussion of the most significant results and conclusions. The scope of the problems discussed here are: the study of a (137)Cs calibration irradiator; the manganese bath technique; the iron sphere experiment using neutron time-of-flight technique; the energy response of a RADFET detector and finally the sensitivity and uncertainty analysis for the recoil-proton telescope discussed in the companion paper.

The Neutrons for Science Facility at SPIRAL-2.

The neutrons for science (NFS) facility is a component of SPIRAL-2, the new superconducting linear accelerator built at GANIL in Caen (France). The proton and deuteron beams delivered by the accelerator will allow producing intense neutron fields in the 100 keV-40 MeV energy range. Continuous and quasi-mono-kinetic energy spectra, respectively, will be available at NFS, produced by the interaction of a deuteron beam on a thick Be converter and by the 7Li(p,n) reaction on thin converter. The pulsed neutron beam, with a flux up to two orders of magnitude higher than those of other existing time-of-flight facilities, will open new opportunities of experiments in fundamental research as well as in nuclear data measurements. In addition to the neutron beam, irradiation stations for neutron-, proton- and deuteron-induced reactions will be available for cross-sections measurements and for the irradiation of electronic devices or biological cells. NFS, whose first experiment is foreseen in 2018, will be a very powerful tool for physics, fundamental research as well as applications like the transmutation of nuclear waste, design of future fission and fusion reactors, nuclear medicine or test and development of new detectors.

Three-dimensional shielding calculations for the IFMIF neutron source using a coupled Monte Carlo/Deterministic computational scheme.

Shielding calculations for the International Fusion Materials Irradiation Facility (IFMIF) are complicated due to the geometrical complexity of the target system and the large-scale bulk shields around the source target. Three-dimensional shielding calculations were performed by using a newly developed Monte Carlo/Deterministic computational scheme. The neutron-photon fluxes and dose rate distributions in the back wall of the Test Cell and the access/maintenance room are presented and compared with previous shielding calculations. The results demonstrate that this coupled scheme is an useful computational tool for three-dimensional shielding analyses of complex and large nuclear facilities.

Nanodiamond finding in the hyblean shallow mantle xenoliths.

Most of Earth's diamonds are connected with deep-seated mantle rocks; however, in recent years, µm-sized diamonds have been found in shallower metamorphic rocks, and the process of shallow-seated diamond formation has become a hotly debated topic. Nanodiamonds occur mainly in chondrite meteorites associated with organic matter and water. They can be synthesized in the stability field of graphite from organic compounds under hydrothermal conditions. Similar physicochemical conditions occur in serpentinite-hosted hydrothermal systems. Herein, we report the first finding of nanodiamonds, primarily of 6 and 10 nm, in Hyblean asphaltene-bearing serpentinite xenoliths (Sicily, Italy). The discovery was made by electron microscopy observations coupled with Raman spectroscopy analyses. The finding reveals new aspects of carbon speciation and diamond formation in shallow crustal settings. Nanodiamonds can grow during the hydrothermal alteration of ultramafic rocks, as well as during the lithogenesis of sediments bearing organic matter.