[en] A new scheme for a FEL operation is proposed. The conventional principle of FEL operation is means that the electron bunch passes through the interaction area of FEL only in one direction. We suggest another possible layout which implies that the electron bunch makes a turn after leaving the wiggler and entries the wiggler at the same end. Actually the wiggler is a kind of a bridge between two storage rings. The electron bunches on the orbit are expected to be adjusted in the way that after one of them leaves the wiggler, another one enters in the opposite direction and in the proper phase with the wave pulse emitted by the previous bunch. So the electron bunch comes in interaction with the amplified electromagnetic wave in both directions i.e. twice per period. It is especially important for the short wavelength FELs, because each reflection from the mirror causes a significant losses of the wave magnitude. The proposed design gives one interaction per each reflection instead of one interaction per two reflections in the traditional scheme. Another way to realize the suggested principle of operating is to insert the wiggler in the electron-positron storage ring. But this layout can be less efficient because of low intensity of the positron beam. The comparison study of radiation from different types of described double wigglers is fulfilled. The synchronization problems are discussed in this paper

[en] The thermodynamic equilibria of the “Fermi–Dirac gas–Maxwell gas–Boltzmann gas” and “metal–saturated vapor” systems are considered (with allowance for charged particles). It is shown that the work function of a metal at 0 K is equal to the Mulliken electronegativity of its atoms. For the latter case, it is proposed to take into account the relationship between the work-function thermal coefficient and the thermodynamic functions of positive and negative metal ions.

[en] The literature data on equilibrium with the participation of cobalt fluorides and their negative ions are analyzed. Enthalpies of formation −∆_fH°(0 K) are determined (kJ/mol): CoF₃, 568.9 ± 8; ${\text{CoF}}_3^{-<!--\; ???\; -->}$, 972.4 ± 10; CoF₄, 639.4 ± 12; ${\text{CoF}}_4^{-<!--\; ???\; -->}$, 1228.0 ± 17.

[en] The DIRAC experiment aims to measure the lifetime of π+π- atoms in the ground state with 10% precision, using the 24 GeV/c proton beam of the CERN Proton Synchrotron. As the value of the above lifetime of order 10-15s is dictated by a strong interaction at low energy, the precise measurement of this quantity enables to determine a combination of S-wave pion scattering lengths to 5%. Pion scattering lengths have been calculated in the framework of chiral perturbation theory with high precision. Thus the accurate measurement of these values would submit the understanding of chiral symmetry breaking of QCD to a crucial test. Some preliminary results from the analysis of a 2000 data sample are presented

[en] Nanoparticles (NPs) are among the most promising agents for advanced theranostics. However, their functioning in vivo is severely inhibited by the mononuclear phagocyte system (MPS), which rapidly removes all foreign entities from blood circulation. Little is known about the sequestration mechanisms and the ways to counteract them. New methods are highly demanded for investigation with high scrutiny of each aspect of NP clearance from blood. For example, while liver macrophages capture the majority of the administered particles, reliable investigation of this process in absence of other MPS components is hard to implement in vivo. Here, we demonstrate a novel method for real-time investigation hepatic uptake of NPs in an isolated perfused liver based on an extremely accurate magnetometric registration technique. The signal is obtained solely from the magnetic NPs without any ‘background’ from blood or tissues, which is a significant advantage over other techniques, e.g. optical ones. We illustrate the method capacity by investigation of behavior of different particles and show good correlation with in vivo studies. We also demonstrate notable suitability of the method for studying the NP clearance from the flow in the user-defined mediums, e.g. those containing specific serum components. Finally, the method was applied to reveal an interesting effect of short-term decrease of liver macrophage activity after the first interaction with small amounts of NPs. The developed perfusion model based on the high-performance magnetometry can be used for finding new mechanisms of NP sequestration and for development of novel ‘stealth’ nanoagents. (paper)

[en] The production of π⁺π^- pairs in the reaction pTa→π⁺π^-X at 70 GeV is studied. For pions with laboratory momenta from 0.8 to 2.4 GeV/c, the two-particle correlation function is measured for c.m.s. relative momenta from the interval 0≤q≤50 MeV/c. For pions produced in the region that is much smaller than 1/m_πα, Coulomb final-state interaction leads to a sharp increase in the yield of π⁺π^- pairs with q<10 MeV/c. The effect of Coulomb interaction allows separation of π⁺π^- pairs according to the size of the region of their production

[en] Biodegradation of a "5"7Fe_3O_4 - based dextran - stabilized ferrofluid in the ventricular cavities of the rat brain was studied by X-ray diffraction and Mössbauer spectroscopy. A two-step process of biodegradation, consisting of fast disintegration of the initial composite magnetic beads into separate superparamagnetic nanoparticles and subsequent slow dissolution of the nanoparticles has been found. Joint fitting of the couples of Mössbauer spectra measured at different temperatures in the formalism of multi-level relaxation model with one set of fitting parameters, allowed us to measure concentration of exogenous iron in the rat brain as a function of time after the injection of nanoparticles.

[en] The main objective of DIRAC experiment is the measurement of the lifetime τ of the exotic hadronic atom consisting of π⁺ and π^- mesons. The lifetime of this atom is determined by the decay mode π⁺ π^- → π⁰ π⁰ due to the strong interaction. Through the precise relationship between the lifetime and the S-wave pion-pion scattering length difference |a₀ - a₂| for isospin 0 and 2 (respectively), a measurement of τ with an accuracy of 10% will allow a determination of |a₀ - a₂| at a 5% precision level. Pion-pion scattering lengths have been calculated in the framework of chiral perturbation theory with an accuracy below 5%. In this way DIRAC experiment will provide a crucial test of the chiral symmetry breaking scheme in QCD effective theories at low energies

[en] The DIRAC spectrometer has been commissioned at CERN with the aim of detecting π⁺π^- atoms produced by a 24 GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to cope with the high interaction rates involved, the triggering of pion pairs with very detector efficiency.ation of the imaging sof the latter with resolution around 0.6 MeV/c. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and set-up performances are also given