Density functional theory of freezing for soft interactions in two dimensions

A density functional theory of two-dimensional freezing is presented for a soft interaction potential that scales as inverse cube of particle distance. This repulsive potential between parallel, induced dipoles is realized for paramagnetic colloids on an interface, which are additionally exposed to an external magnetic field. An extended modified weighted density approximation which includes correct triplet correlations in the liquid state is used. The theoretical prediction of the freezing transition is in good agreement with experimental and simulation data.Comment: 7 pages, 3 figures, submitted 200

Robustness of "cut and splice" genetic algorithms in the structural optimization of atomic clusters

We return to the geometry optimization problem of Lennard-Jones clusters to analyze the performance dependence of "cut and splice" genetic algorithms (GAs) on the employed population size. We generally find that admixing twinning mutation moves leads to an improved robustness of the algorithm efficiency with respect to this a priori unknown technical parameter. The resulting very stable performance of the corresponding mutation+mating GA implementation over a wide range of population sizes is an important feature when addressing unknown systems with computationally involved first-principles based GA sampling.Comment: 5 pages including 3 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Spin Precession and Oscillations in Mesoscopic Systems

We compare and contrast magneto-transport oscillations in the fully quantum (single-electron coherent) and classical limits for a simple but illustrative model. In particular, we study the induced magnetization and spin current in a two-terminal double-barrier structure with an applied Zeeman field between the barriers and spin disequilibrium in the contacts. Classically, the spin current shows strong tunneling resonances due to spin precession in the region between the two barriers. However, these oscillations are distinguishable from those in the fully coherent case, for which a proper treatment of the electron phase is required. We explain the differences in terms of the presence or absence of coherent multiple wave reflections.Comment: 9 pages, 5 figure

Field exposed water in a nanopore: liquid or vapour?

We study the behavior of ambient temperature water under the combined effects of nanoscale confinement and applied electric field. Using molecular simulations we analyze the thermodynamic causes of field-induced expansion at some, and contraction at other conditions. Repulsion among parallel water dipoles and mild weakening of interactions between partially aligned water molecules prove sufficient to destabilize the aqueous liquid phase in isobaric systems in which all water molecules are permanently exposed to a uniform electric field. At the same time, simulations reveal comparatively weak field-induced perturbations of water structure upheld by flexible hydrogen bonding. In open systems with fixed chemical potential, these perturbations do not suffice to offset attraction of water into the field; additional water is typically driven from unperturbed bulk phase to the field-exposed region. In contrast to recent theoretical predictions in the literature, our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale channels and nanoporous materials.Comment: 20 pages, 6 figures + T.O.C. figure, in press in PCC

Superparamagnetic colloids in viscous fluids

The influence of a magnetic field on the aggregation process of superparamagnetic colloids has been well known on short time for a few decades. However, the influence of important parameters, such as viscosity of the liquid, has received only little attention. Moreover, the equilibrium state reached after a long time is still challenging on some aspects. Indeed, recent experimental measurements show deviations from pure analytical models in extreme conditions. Furthermore, current simulations would require several years of computing time to reach equilibrium state under those conditions. In the present paper, we show how viscosity influences the characteristic time of the aggregation process, with experimental measurements in agreement with previous theories on transient behaviour. Afterwards, we performed numerical simulations on equivalent systems with lower viscosities. Below a critical value of viscosity, a transition to a new aggregation regime is observed and analysed. We noticed this result can be used to reduce the numerical simulation time from several orders of magnitude, without modifying the intrinsic physical behaviour of the particles. However, it also implies that, for high magnetic fields, granular gases could have a very different behaviour from colloidal liquids

Международное сотрудничество Республики Беларусь в содействии устойчивому развитию и продвижении прав человека

Key words: foreign policy of the Republic of Belarus; international cooperation; the UN; sustainable development; human rights; overcoming of poverty and social inequality. = Ключевые слова: внешняя политика Республики Беларусь; международное сотрудничество; ООН; устойчивое развитие; права человека; преодоление бедности и социального неравенства.Promotion of human rights, progress in the sustainable development and overcoming of different forms of poverty on the national, regional and global level is one of the most important directions of the multilateral diplomacy of the Re-public of Belarus since its independence in 1991. Based on an international experience of the Belarusian SSR as one of the United Nations founders in its main bodies, primarily the Economic and Social Council (ECOSOC), as well as its special institutions, the Belarusian diplomacy has already established mutually beneficial and effective cooperation with other countries in many important issues. Among them, there are such key and acute topics as a fighting against poverty and unequal access to social benefits and achievements, as well as overcoming regional and structural imparities for different social groups and communities. This comprehensive dialogue with our leading international partners including a special role of our partnership with China continued and developed successfully in the early 21st century. It allowed the Republic of Belarus to contribute to the modern understanding of human rights in the context of global sustainable development. Achieving its Goals (SDGs) until 2030, agreed by all UN members is one of the most important aspects and challenges for the policy of the Republic of Belarus and for its primary vision of the promotion of human rights issues in the global world. Our understanding of them is based on their universal, indivisible, interrelated, interdependent and complementary nature. To ensure each of their most important categories: civil, political, economic, social, cultural it should be adhere to the same positions and attitudes with equal attention. International cooperation in this sphere is to be aimed at strengthening mutual trust and developing effective multilateral mechanisms to solve the most important global problems. The Republic of Belarus opposes consistently and resolutely any attempts to politicize them and calls for a comprehensive approach to the protection of all categories of human rights and liberties in the framework of international cooperation with-out prioritizing or minimizing them.Продвижение прав человека, прогресс в области устойчивого развития и преодоление различных форм бедности на национальном, региональном и глобальном уровнях являются одним из важнейших направлений многосторонней дипломатии Республики Беларусь с момента обретения независимости в 1991 г. Опираясь на международный опыт Белорусской ССР как одного из основателей ООН, полученный в результате работы в ее основных органах, прежде всего Экономическом и социальном совете, а также специальных учреждениях, белорусская дипломатия наладила взаимовыгодное и эффективное сотрудничество с другими странами в решении многих важных проблем. Среди них такие ключевые и злободневные темы, как борьба с бедностью и неравным доступом к социальным благам и достижениям, а также преодоление регионального и структурного неравенства различных социальных групп и общностей. Всесторонний диалог с нашими ведущими международными партнерами, включая особую роль сотрудничества с Китаем, продолжался и успешно развивался в начале XXI в. Это позволило Республике Беларусь внести свой вклад в современное понимание прав человека в контексте глобального устойчивого развития. Достижение его целей (ЦУР) до 2030 г., согласованное всеми членами ООН, является одной из наиболее важных задач для политики Республики Беларусь и ее основополагающего видения продвижения прав человека в глобальном мире. Наше их понимание основывается на универсальном, неделимом, взаимосвязанном, взаимозависимом и взаимодополняющем характере. В деле обеспечения каждой из наиболее важных категорий прав человека: гражданских, политических, экономических, социальных, культурных следует придерживаться одинаковых позиций и относиться к ним с равным вниманием. Международное сотрудничество в этой сфере должно быть направлено на укрепление взаимного доверия и разработку эффективных многосторонних механизмов для решения важнейших глобальных проблем. Республика Беларусь последовательно и решительно выступает против любых попыток их политизации и призывает к комплексному подходу к соблюдению всех категорий прав и свобод человека в рамках международного сотрудничества, не пытаясь выделить среди них приоритетные или свести их к минимуму