Mode locking of vortex matter driven through mesoscopic channels

We investigated the driven dynamics of vortices confined to mesoscopic flow channels by means of a dc-rf interference technique. The observed mode-locking steps in the $IV$-curves provide detailed information on how the number of rows and lattice structure in the channel change with magnetic field. Minima in flow stress occur when an integer number of rows is moving coherently, while maxima appear when incoherent motion of mixed $n$ and $n\pm 1$ row configurations is predominant. Simulations show that the enhanced pinning at mismatch originates from quasi-static fault zones with misoriented edge dislocations induced by disorder in the channel edges.Comment: some minor changes were made, 4 pages, 4 figures, accepted for publication in Phys. Rev. Let

Пріоритети вдосконалення фінансової політики і структури зайнятості в бюджетному і промисловому секторах економіки

Обґрунтовано проблеми взаємозв’язку фінансування, зайнятості, віддачі праці та капіталу. Висвітлено засади формування фінансової політики, удосконалення структури зайнятості у бюджетному та промисловому секторах економіки України. Ключові слова: фінансова політика, зайнятість, проблеми, економіка України. -----Обосновываются проблемы взаимосвязи финансирования, занятости, отдачи труда и капитала. Освещаются принципы формирования финансовой политики, усовершенствования структуры занятости в бюджетном и промышленном секторах украинской экономики. Ключевые слова: финансовая политика, занятость, проблемы, украинская экономика. ------Problems concerning interrelations between financing, employment, return on labour and capital are grounded. Principles of forming the financial policy, improvements in the structure of employment in the budgetary and industrial sectors of the economy of Ukraine are described. Key words: financial policy, employment, problems, economy of Ukraine. ----

Single File Diffusion enhancement in a fluctuating modulated 1D channel

We show that the diffusion of a single file of particles moving in a fluctuating modulated 1D channel is enhanced with respect to the one in a bald pipe. This effect, induced by the fluctuations of the modulation, is favored by the incommensurability between the channel potential modulation and the moving file periodicity. This phenomenon could be of importance in order to optimize the critical current in superconductors, in particular in the case where mobile vortices move in 1D channels designed by adapted patterns of pinning sites.Comment: 4 pages, 4 figure

Quasi-chemical Theories of Associated Liquids

It is shown how traditional development of theories of fluids based upon the concept of physical clustering can be adapted to an alternative local clustering definition. The alternative definition can preserve a detailed valence description of the interactions between a solution species and its near-neighbors, i.e., cooperativity and saturation of coordination for strong association. These clusters remain finite even for condensed phases. The simplest theory to which these developments lead is analogous to quasi-chemical theories of cooperative phenomena. The present quasi-chemical theories require additional consideration of packing issues because they don't impose lattice discretizations on the continuous problem. These quasi-chemical theories do not require pair decomposable interaction potential energy models. Since calculations may be required only for moderately sized clusters, we suggest that these quasi-chemical theories could be implemented with computational tools of current electronic structure theory. This can avoid an intermediate step of approximate force field generation.Comment: 20 pages, no figures replacement: minor typographical corrections, four references added, in press Molec. Physics 199

Анализ влияния глобальных угроз на устойчивое развитие стран и регионов мира с помощью байесовских сетей доверия

Застосовано байєсівські мережі довіри для встановлення на якісному рівні причинно-наслідкових залежностей між глобальними загрозами і індексами сталого розвитку. Використання запропонованих в роботі методів синтезу мережі довіри та узагальнення результатів моделвання дозволило отримати цілісну інтерпетацію процесів впливу глобальних загроз на сталий розвиток країн і регіонів світу.Belief Bayesian Networks are used to establish the qualitative cause-effect relationships between global threats and indices of sustainable development. The method of belief network synthesis and the method of final results generalization were proposed. This made it possible to obtain a holistic understanding of effects of global threats to the sustainable development of countries and regions of the world

Multiple shear-banding transitions in a supramolecular polymer solution

We report on the nonlinear rheology of a reversible supramolecular polymer based on hydrogen bonding. The coupling between the flow-induced chain alignment and breakage and recombination of bonds between monomers leads to a very unusual flow behavior. Measured velocity profiles indicate three different shear-banding regimes upon increasing shear rate, each with different characteristics. While the first of these regimes has features of a mechanical instability, the second shear-banding regime is related to a shear-induced phase separation and the appearance of birefringent textures. The shear-induced phase itself becomes unstable at very high shear rates, giving rise to a third banding regime

Dynamic ordering and frustration of confined vortex rows studied by mode-locking experiments

The flow properties of confined vortex matter driven through disordered mesoscopic channels are investigated by mode locking (ML) experiments. The observed ML effects allow to trace the evolution of both the structure and the number of confined rows and their match to the channel width as function of magnetic field. From a detailed analysis of the ML behavior for the case of 3-rows we obtain ({\it i}) the pinning frequency $f_p$, ({\it ii}) the onset frequency $f_c$ for ML ($\propto$ ordering velocity) and ({\it iii}) the fraction $L_{ML}/L$ of coherently moving 3-row regions in the channel. The field dependence of these quantities shows that, at matching, where $L_{ML}$ is maximum, the pinning strength is small and the ordering velocity is low, while at mismatch, where $L_{ML}$ is small, both the pinning force and the ordering velocity are enhanced. Further, we find that $f_c \propto f_p^2$, consistent with the dynamic ordering theory of Koshelev and Vinokur. The microscopic nature of the flow and the ordering phenomena will also be discussed.Comment: 10 pages, 7 figure, submitted to PRB. Discussion has been improved and a figure has been adde

Dynamic mode locking in a driven colloidal system: experiments and theory

In this article we examine the dynamics of a colloidal particle driven by a modulated force over a sinusoidal optical potential energy landscape. Coupling between the competing frequencies of the modulated drive and that of particle motion over the periodic landscape leads to synchronisation of particle motion into discrete modes. This synchronisation manifests as steps in the average particle velocity, with mode locked steps covering a range of average driving velocities. The amplitude and frequency dependence of the steps are considered, and compared to results from analytic theory, Langevin dynamics simulations, and dynamic density functional theory. Furthermore, the critical driving velocity is studied, and simulation used to extend the range of conditions accessible in experiments alone. Finally, state diagrams from experiment, simulation, and theory are used to show the extent of the dynamically locked modes in two dimensions, as a function of both the amplitude and frequency of the modulated drive