Higher order glass-transition singularities in colloidal systems with attractive interactions

The transition from a liquid to a glass in colloidal suspensions of particles interacting through a hard core plus an attractive square-well potential is studied within the mode-coupling-theory framework. When the width of the attractive potential is much shorter than the hard-core diameter, a reentrant behavior of the liquid-glass line, and a glass-glass-transition line are found in the temperature-density plane of the model. For small well-width values, the glass-glass-transition line terminates in a third order bifurcation point, i.e. in a A_3 (cusp) singularity. On increasing the square-well width, the glass-glass line disappears, giving rise to a fourth order A_4 (swallow-tail) singularity at a critical well width. Close to the A_3 and A_4 singularities the decay of the density correlators shows stretching of huge dynamical windows, in particular logarithmic time dependence.Comment: 19 pages, 12 figures, Phys. Rev. E, in prin

Характеристика горных пород рудного месторождения Бухадры в Алжире

Currently, the calculation of the sustainability of the mountain range is one of the main tasks during the design of underground structures at the Bukhadra ore deposit. Each technique involves its own calculation and classification of categories of sustainability. This article presents the results of our research. As a result of laboratory studies, the physical properties of the samples were studied. For each sample, the density, porosity, the degree of saturation of the soil with water, and the degree of cracking of rocks were determined. As a result of the research, it can be concluded that the rocks of the Bukhardra iron mine are very resistant to various factors. A classification developed by the Norwegian Geotechnical Institute to classify mountain ranges and predict further work was used to analyze the rocks of the Bukhadra iron mine. It should be noted that in order to understand the variability of the strength characteristics of the ore, the rock strength index is used. It is a leading indicator of poor quality rock zones. According to the physico-mechanical tests in the laboratories, it was noted that the Bukhadra mine massif has good resistance to compression, tension and shear, this suggests that stability problems in this field are associated with technical factors, such as surface and underground mining.В настоящее время расчет устойчивости горного массива является одной из основных задач в период проектирования подземных сооружений на рудном месторождении Бухадры. Каждая методика предполагает собственный расчет и классификацию категорий устойчивости. В данной статье представлены результаты лабораторных исследований физических свойств образцов горных пород. Для каждого образца были определены плотность, пористость, степень насыщения грунта водой, степень растрескивания. По результатам проведенных работ можно сделать вывод о том, что горные породы железного рудника Бухарды очень устойчивы к воздействию различных факторов. Для анализа горных пород железного рудника Бухадры с целью классификации горных массивов и прогнозирования дальнейших работ была использована классификация, разработанная Норвежским геотехническим институтом. Следует отметить, что для понимания изменчивости прочностных характеристик руды используется показатель прочности пород. Это ведущий индикатор зон скальных пород низкого качества. Согласно физико-механическим испытаниям в лабораториях, отмечено, что массив рудника Бухадры имеет хорошую устойчивость к сжатию, растяжению и сдвигу. Это говорит о том, что проблемы устойчивости на данном месторождении связаны с техническими факторами, такими как поверхностная и подземная добыча полезных ископаемых

Effect of microstructures on the electron-phonon interaction in the disordered metals Pd60_{60}Ag40_{40}

Using the weak-localization method, we have measured the electron-phonon scattering times $\tau_{ep}$ in Pd$_{60}$Ag$_{40}$ thick films prepared by DC- and RF-sputtering deposition techniques. In both series of samples, we find an anomalous $1/\tau_{ep} \propto T^2\ell$ temperature and disorder dependence, where $\ell$ is the electron elastic mean free path. This anomalous behavior cannot be explained in terms of the current concepts for the electron-phonon interaction in impure conductors. Our result also reveals that the strength of the electron-phonon coupling is much stronger in the DC than RF sputtered films, suggesting that the electron-phonon interaction not only is sensitive to the total level of disorder but also is sensitive to the microscopic quality of the disorder.Comment: accepted for publication in Phys. Rev.

JINR activity in microwave sources for TeV range linear colliders

Results of theoretical and experimental studies of the microwave radiation sources on the base of the induction linac LIU-3000 (JINR, Dubna) are presented. In particular, a FEM-oscillator with the reversed guide magnetic field and Bragg resonator as well as an electron beam buncher in the two-beam accelerator (TBA) driver was studied

Current-induced highly dissipative domains in high Tc thin films

We have investigated the resistive response of high Tc thin films submitted to a high density of current. For this purpose, current pulses were applied into bridges made of Nd(1.15)Ba(1.85)Cu3O7 and Bi2Sr2CaCu2O8. By recording the time dependent voltage, we observe that at a certain critical current j*, a highly dissipative domain develops somewhere along the bridge. The successive formation of these domains produces stepped I-V characteristics. We present evidences that these domains are not regions with a temperature above Tc, as for hot spots. In fact this phenomenon appears to be analog to the nucleation of phase-slip centers observed in conventional superconductors near Tc, but here in contrast they appear in a wide temperature range. Under some conditions, these domains will propagate and destroy the superconductivity within the whole sample. We have measured the temperature dependence of j* and found a similar behavior in the two investigated compounds. This temperature dependence is just the one expected for the depairing current, but the amplitude is about 100 times smaller.Comment: 9 pages, 9 figures, Revtex, to appear in Phys. Rev.

Gravitationally lensed QSOs in the ISSIS/WSO-UV era

Gravitationally lensed QSOs (GLQs) at redshift z = 1-2 play a key role in understanding the cosmic evolution of the innermost parts of active galaxies (black holes, accretion disks, coronas and internal jets), as well as the structure of galaxies at intermediate redshifts. With respect to studies of normal QSOs, GLQ programmes have several advantages. For example, a monitoring of GLQs may lead to unambiguous detections of intrinsic and extrinsic variations. Both kinds of variations can be used to discuss central engines in distant QSOs, and mass distributions and compositions of lensing galaxies. In this context, UV data are of particular interest, since they correspond to emissions from the immediate surroundings of the supermassive black hole. We describe some observation strategies to analyse optically bright GLQs at z of about 1.5, using ISSIS (CfS) on board World Space Observatory-Ultraviolet.Comment: 7 pages, 4 figures, Accepted for publication in Astrophysics & Space Scienc

Free electron lasers based on LINAC-800

The project “FELs and LINAC-800” is being under development at JINR. It is based on an accelerator facility presented to JINR by NIKHEF, Amsterdam. Analysis has shown that it is possible to build in Dubna a universal light source with unique characteristics consisting of a complex of Free Electron Lasers (FEL) covering continuously the wavelength range from far-infrared (150 µm) down to ultraviolet (150 nm). Besides, LINAC-800 could be used for different applications and as an injector for the next generation synchrotron radiation source.Проект ЛСЭ и ЛИНАК-800 реализуется в ОИЯИ. Он основан на ускорительном оборудовании, предоставленном ОИЯИ NIKHEF (Амстердам). Анализ показывает, что в Дубне станет возможным сооружение универсального источника с уникальными характеристиками, состоящего из комплекса лазеров на свободных электронах (ЛСЭ), покрывающих непрерывно длины волн от дальнего инфракрасного излучения (150 мкм) до ультрафиолета (150 нм).Проект ЛСЕ і ЛІНАК-800 реалізується в ОІЯД. Він заснований на прискорювальному устаткуванні, що було дано ОІЯД NІKHEF (Амстердам). Аналіз показує, що в Дубні стане можливим спорудження універсального джерела з унікальними характеристиками, що складається з комплексу лазерів на вільних електронах (ЛВЕ), що перекривають безперервно довжини хвиль від далекого інфрачервоного випромінювання (150 мкм) до ультрафіолету (150 нм)

Large enhancement of deuteron polarization with frequency modulated microwaves

We report a large enhancement of 1.7 in deuteron polarization up to values of 0.6 due to frequency modulation of the polarizing microwaves in a two liters polarized target using the method of dynamic nuclear polarization. This target was used during a deep inelastic polarized muon-deuteron scattering experiment at CERN. Measurements of the electron paramagnetic resonance absorption spectra show that frequency modulation gives rise to additional microwave absorption in the spectral wings. Although these results are not understood theoretically, they may provide a useful testing ground for the deeper understanding of dynamic nuclear polarization.Comment: 10 pages, including the figures coming in uuencoded compressed tar files in poltar.uu, which also brings cernart.sty and crna12.sty files neede

Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly

Astronomical Distance Determination in the Space Age: Secondary Distance Indicators

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)