Metastable phases and "metastable" phase diagrams

The work discusses specifics of phase transitions for metastable states of substances. The objects of condensed media physics are primarily equilibrium states of substances with metastable phases viewed as an exception, while the overwhelming majority of organic substances investigated in chemistry are metastable. It turns out that at normal pressure many of simple molecular compounds based on light elements (these include: most hydrocarbons; nitrogen oxides, hydrates, and carbides; carbon oxide (CO); alcohols, glycerin etc) are metastable substances too, i.e. they do not match the Gibbs' free energy minimum for a given chemical composition. At moderate temperatures and pressures, the phase transitions for given metastable phases throughout the entire experimentally accessible time range are reversible with the equilibrium thermodynamics laws obeyed. At sufficiently high pressures (1-10 GPa), most of molecular phases irreversibly transform to more energy efficient polymerized phases, both stable and metastable. These transformations are not consistent with the equality of the Gibbs' free energies between the phases before and after the transition, i.e. they are not phase transitions in "classical" meaning. The resulting polymeric phases at normal pressure can exist at temperatures above the melting one for the initial metastable molecular phase. Striking examples of such polymers are polyethylene and a polymerized modification of CO. Many of energy-intermediate polymeric phases can apparently be synthesized by the "classical" chemistry techniques at normal pressure.Comment: 5 pages, 4 figure

Down-regulation of murine beta-defensin-2 in Lewis lung carcinoma cells results in accelerated growth of tumor cells in vitro and in vivo

To evaluate the anti-tumor activity of murine beta-defensin-2 (mBD-2) expression in vitro and in vivo. Materials and Methods: Based on pcDNA3 vector, constructs containing mBD-2 cDNA coding mature defensin molecule (pcDNA3-mBD2), and Igk-mBD-2 insertion, coding secretory sequence plus mature defensin molecule (pcDNA3-Igk-mBD-2) were generated. Lewis lung carcinoma (3LL) cells were transfected in vitro with these plasmids and with blank pcDNA3 vector, and the proliferative rate and clonogenic ability of obtained cell lines cultivated in vitro were analyzed using 3H-incorporation technique and colony formation in semi-soft medium, respectively. Expression of mBD-2 mRNA was studied by semiquantative RT-PCR analysis. Also, transfected cells were transplanted to C57B mice, and the patterns of tumor growth in vivo were analyzed by routine techniques. Results: We have found out that in the 3LL cells transfected with pcDNA3-mBD-2 and pcDNA3-Igk-mBD-2, the expression of mBD-2 mRNA is significantly down regulated compared to wild-type cells and 3LL cells transfected with blank vector. The cells with suppressed mBD-2 expression differed from parental cells and cells transfected with blank vector by higher proliferation rate (p < 0.001) and higher clonogenic ability. The 3LL-mBD-2 and 3LL-Igk-mBD-2 cells that are transplanted to C57B mice gave rise to more aggressive tumors that possessed significantly higher growth rate (p < 0.01) than those that arise from wild-type 3LL cells. Conclusion: The obtained results are evidencing on a possible tumor-suppressing role of mBD-2 expression.Цель: настоящая работа посвящена анализу противоопухолевых свойств бета-дефенсина-2 мыши (mBD-2) in vitro and in vivo. Материалы и методы: на основе pcDNA3.1+ вектора были созданы 2 плазмидных конструкта, кодирующих зрелую форму mBD-2, содержащие или несодержащие сигнальную последовательность Igk (pcDNA3mBD-2 и pcDNA3Igk-mBD-2 соответственно). Путем трансфекции клеток 3LL полученными векторами, а также контрольным вектором pcDNA3.1+ были получены клеточные линии (3LL-mBD-2, 3LL-Igk-mBD-2 и 3LL-pcDNA3), для которых были проведены исследования их пролиферативной активности, определенной по уровню включения 3 Н-тимидина в ДНК, и способности к колониеобразованию в среде, содержащей метилцеллюлозу. Экспрессию гена mBD-2 исследовали с помощью полуколичественного ОТ-ПЦР-анализа. Трансфецированные клетки были имплантированы мышам линии C57BL, после чего была проанализирована динамика роста опухоли. Результаты: установлено, что в трансфектных клеточных линиях 3LL-mBD-2 и 3LL-Igk-mBD-2 уровень экспрессии mBD-2 снижен по сравнению с контрольными. Эти клетки характеризовались достоверным повышением уровня пролиферации (р < 0,001) и способности к колониеобразованию. Клетки сублиний 3LLmBD-2 и 3LL-Igk-mBD-2, трансплантированные мышам линии C57BL, вызывали развитие более агрессивных опухолей, обладающих значительно более высокой скоростью роста (p < 0,01), чем таковые, вызванные перевивкой клеток 3LL. Выводы: полученные результаты свидетельствуют о возможной роли mBD-2 как опухолевого супрессора

Measuring the Density Matrix by Local Addressing

We introduce a procedure to measure the density matrix of a material system. The density matrix is addressed locally in this scheme by applying a sequence of delayed light pulses. The procedure is based on the stimulated Raman adiabatic passage (STIRAP) technique. It is shown that a series of population measurements on the target state of the population transfer process yields unambiguous information about the populations and coherences of the addressed states, which therefore can be determined.Comment: 4 pages, 1 figur

Monodisperse gas-solid mixtures with intense interphase interaction in two-fluid smoothed particle hydrodynamics

Simulations of gas-solid mixtures are used in many scientific and industrial applications. Two-Fluid Smoothed Particle Hydrodynamics (TFSPH) is an approach when gas and solids are simulated with different sets of particles interacting via drag force. Several methods are developed for computing drag force between gas and solid grains for TFSPH. Computationally challenging are simulations of gas-dust mixtures with intense in- tephase interaction, when velocity relaxation time tstop is much smaller than dynamical time of the problem. In explicit schemes the time step τ must be less than tstop, that leads to high computational costs. Moreover, it is known that for stiff problems both grid-based and particle methods may require unaffordably detailed resolution to capture the asymptotical bahaiviour of the solution. To address this problem we developed fast and robust method for computing stiff and mild drag force in gas solid-mixtures based on the ideas of Particle-in-Cell approach. In the paper we compare the results of new and previously developed methods on test problems