Гидродинамическое диспергирование кальций-алюмосиликатных материалов из техногенного и нерудного сырья

Physicochemical properties of two calcium aluminosilicate materials after reducing in the hydrodynamic rotary generator in supercavitation mode were studied. The samples are the crystal ceramic foam based on Kansko-Achinsk lignite-ash and the porous glass material obtained from low-manganese nonmetallic feed. X-ray phase analysis, EPR-method, NPR-method (the Mossbauer Effect) and optical microscopy were used. It was found that the material is changing its stucrure in a hydrodynamic dispersion process caused by high-cavitation. The nature of the changes depends on its initial stateИзучены физико-химические свойства двух кальций-алюмосиликатных материалов после измельчения в гидродинамическом генераторе роторного типа в режиме суперкавитации. Исследованы образцы – кристаллическая пенокерамика на основе зол бурых Канско-Ачинских углей и пористый стекломатериал, полученный из нерудного сырья с низким содержанием марганца. Для анализа были использованы методы РФА, ЭМР, ЯГР (эффект Мёссбауэра), оптическая микроскопия. Показано, что в процессе гидродинамического диспергирования за счет высокоэнергетического кавитационного воздействия в материалах происходят глубокие структурные изменения. Получено, что характер изменений зависит от исходного состояния исследуемого материал

Probing superfast quarks in nuclei through dijet production at the LHC

We investigate dijet production from proton-nucleus collisions at the Large Hadron Collider (LHC) as a means for observing superfast quarks in nuclei with Bjorken $x>1$. Kinematically, superfast quarks can be identified through directly measurable jet kinematics. Dynamically, their description requires understanding several elusive properties of nuclear QCD, such as nuclear forces at very short distances, as well as medium modification of parton distributions in nuclei. In the present work, we develop a model for nuclear parton distributions at large $x$ in which the nuclear dynamics at short distance scales are described by two- and three-nucleon short range correlations (SRCs). Nuclear modifications are accounted for using the color screening model, and an improved description of the EMC effect is reached by using a structure function parametrization that includes higher-twist contributions. We apply QCD evolution at the leading order to obtain nuclear parton distributions in the kinematic regime of the LHC, and based on the obtained distributions calculate the cross section for dijet production. We find not only that superfast quarks can be observed at the LHC, but also that they provide sensitivity to the practically unexplored three-nucleon SRCs in nuclei. Additionally, the LHC can extend our knowledge of the EMC effect to large $Q^2$ where higher-twist effects are negligible.Comment: 44 pages, 17 figures, final version to be published in EJP

Secondary proton flux induced by cosmic ray interactions with the atmosphere

The atmospheric secondary proton flux is studied for altitudes extending from sea level up to the top of atmosphere by means of a 3-dimensional Monte-Carlo simulation procedure successfully used previously to account for flux measurements of protons, light nuclei, and electrons-positrons below the geomagnetic cutoff (satellite data), and of muons and antiprotons (balloon data). The calculated flux are compared with the experimental measurements from sea level uo to high float ballon altitudes. The agreement between data and simulation results are very good at all altitudes, including the lowest ones, where the calculations become extremely sensitive to the proton production cross section. The results are discussed in this context. The calculations are extended to the study of quasi trapped particles above the atmosphere to about 5 Earth radii, for prospective purpose.Comment: 7 pages, 5 figures, submitted to Phys. Rev.

Magnetic properties of bottom sediments of Lake Shira (Siberia, Russia)

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Magnetic properties were studied in bottom sediments of saline meromictic Shira Lake by the methods of static magnetometry and resonance Mössbauer spectroscopy for the first time. All layers of bottom sediments contain nanosized single-domain magnetite particles produced by magnetotactic bacteria. The concentration of magnetite in bottom sediments decreased with depth, reaching a local minimum in the layer corresponding to the minimal level of the lake observed in 1910–1930. It is demonstrated that biogenic magnetite may indicate climate-related changes in the level of Shira Lake, in addition to the other biological and geochemical characteristics

Magnetic properties of bottom sediments of Lake Shira (Siberia, Russia)

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.Magnetic properties were studied in bottom sediments of saline meromictic Shira Lake by the methods of static magnetometry and resonance Mössbauer spectroscopy for the first time. All layers of bottom sediments contain nanosized single-domain magnetite particles produced by magnetotactic bacteria. The concentration of magnetite in bottom sediments decreased with depth, reaching a local minimum in the layer corresponding to the minimal level of the lake observed in 1910–1930. It is demonstrated that biogenic magnetite may indicate climate-related changes in the level of Shira Lake, in addition to the other biological and geochemical characteristics

Formation and evolution of magnetic nanoparticles in borate glass simultaneously doped with Fe and Mn oxides

Evolution of the phase state of paramagnetic additions at various stages of synthesis and subsequent thermal treatment of glasses of the system Al2O3-K2O-B2O3 simultaneously doped with Fe2O3 and MnO is studied by means of a combination of experimental techniques: Faraday rotation (FR), electron magnetic resonance (EMR), transmission electron microscopy (TEM), Mössbauer spectroscopy, and magnetic measurements. Both FR and EMR show that magnetically ordered clusters occur already at the first stage of the glass preparation. In particular, for the ratio of the Fe and Mn oxides in the charge close to 3:2, fine magnetic nanoparticles are formed with characteristics similar to those of manganese ferrite. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of these nanoparticles is confirmed and their mean diameter is estimated as approximately 3.2 nm. In the thermally treated glasses larger magnetic nanoparticles are formed, giving rise to FR spectra, characteristic of magnetically ordered systems, and the EMR spectra different from those in as-prepared glasses but also showing superparamagnetic narrowing. The Mössbauer spectroscopy corroborates the manganese ferrite structure of the nanoparticles and indicates their coexistence in the ferrimagnetic and superparamagnetic states. The TEM shows the presence of polydisperse nanoparticles on the background of the glass matrix, and electron diffraction of a selected region containing larger particles indicates a crystal structure close to that of MnFe2O4. Energy-dispersive atomic x-ray spectra confirm that the major part of Fe and Mn introduced to the glass composition is gathered in the particles, with the concentration ratio close to 2:1, characteristic of bulk MnFe2O4. Magnetic hysteresis loops of samples subjected to an additional thermal treatment demonstrate a strong increase in the coercive force, remnant magnetization, and high-field magnetic susceptibility with temperature decrease. The consistent results obtained using various techniques demonstrate that the formation of nanoparticles with characteristics close to those of MnFe2O4 confers to these glasses magnetic and magneto-optical properties typical of substances possessing magnetic order