Orbital Properties of Sr3Ru2O7 and Related Ruthenates Probed by 17O-NMR

We report a site-separated $^{17}$O-NMR study of the layered perovskite ruthenate Sr$_3$Ru$_2$O$_7$, which exhibits nearly two-dimensional transport properties and itinerant metamagnetism at low temperatures. The local hole occupancies and the spin densities in the oxygen $2p$ orbitals are obtained by means of tight-binding analyses of electric field gradients and anisotropic Knight shifts. These quantities are compared with two other layered perovskite ruthenates: the two-dimensional paramagnet Sr$_2$RuO$_4$ and the three-dimensional ferromagnet SrRuO$_3$. The hole occupancies at the oxygen sites are very large, about one hole per ruthenium atom. This is due to the strong covalent character of the Ru-O bonding in this compound. The magnitude of the hole occupancy might be related to the rotation or tilt of the RuO$_6$ octahedra. The spin densities at the oxygen sites are also large, 20-40% of the bulk susceptibilities, but in contrast to the hole occupancies, the spin densities strongly depend on the dimensionality. This result suggests that the density-of-states at the oxygen sites plays an essential role for the understanding of the complex magnetism found in the layered perovskite ruthenates.Comment: 9 pages, 5 figures, to be published in Phys. Rev.

Quantum System under Periodic Perturbation: Effect of Environment

In many physical situations the behavior of a quantum system is affected by interaction with a larger environment. We develop, using the method of influence functional, how to deduce the density matrix of the quantum system incorporating the effect of environment. After introducing characterization of the environment by spectral weight, we first devise schemes to approximate the spectral weight, and then a perturbation method in field theory models, in order to approximately describe the environment. All of these approximate models may be classified as extended Ohmic models of dissipation whose differences are in the high frequency part. The quantum system we deal with in the present work is a general class of harmonic oscillators with arbitrary time dependent frequency. The late time behavior of the system is well described by an approximation that employs a localized friction in the dissipative part of the correlation function appearing in the influence functional. The density matrix of the quantum system is then determined in terms of a single classical solution obtained with the time dependent frequency. With this one can compute the entropy, the energy distribution function, and other physical quantities of the system in a closed form. Specific application is made to the case of periodically varying frequency. This dynamical system has a remarkable property when the environmental interaction is switched off: Effect of the parametric resonance gives rise to an exponential growth of the populated number in higher excitation levels, or particle production in field theory models. The effect of the environment is investigated for this dynamical system and it is demonstrated that there existsComment: 55 pages, LATEX file plus 13 PS figures. A few calculational mistatkes and corresponding figure 1 in field theory model corrected and some changes made for publication in Phys. Rev.D (in press

The cross-frequency mediation mechanism of intracortical information transactions

In a seminal paper by von Stein and Sarnthein (2000), it was hypothesized that "bottom-up" information processing of "content" elicits local, high frequency (beta-gamma) oscillations, whereas "top-down" processing is "contextual", characterized by large scale integration spanning distant cortical regions, and implemented by slower frequency (theta-alpha) oscillations. This corresponds to a mechanism of cortical information transactions, where synchronization of beta-gamma oscillations between distant cortical regions is mediated by widespread theta-alpha oscillations. It is the aim of this paper to express this hypothesis quantitatively, in terms of a model that will allow testing this type of information transaction mechanism. The basic methodology used here corresponds to statistical mediation analysis, originally developed by (Baron and Kenny 1986). We generalize the classical mediator model to the case of multivariate complex-valued data, consisting of the discrete Fourier transform coefficients of signals of electric neuronal activity, at different frequencies, and at different cortical locations. The "mediation effect" is quantified here in a novel way, as the product of "dual frequency RV-coupling coefficients", that were introduced in (Pascual-Marqui et al 2016, http://arxiv.org/abs/1603.05343). Relevant statistical procedures are presented for testing the cross-frequency mediation mechanism in general, and in particular for testing the von Stein & Sarnthein hypothesis.Comment: https://doi.org/10.1101/119362 licensed as CC-BY-NC-ND 4.0 International license: http://creativecommons.org/licenses/by-nc-nd/4.0

Analytic models for mechanotransduction: gating a mechanosensitive channel

Analytic estimates for the forces and free energy generated by bilayer deformation reveal a compelling and intuitive model for MscL channel gating analogous to the nucleation of a second phase. We argue that the competition between hydrophobic mismatch and tension results in a surprisingly rich story which can provide both a quantitative comparison to measurements of opening tension for MscL when reconstituted in bilayers of different thickness and qualitative insights into the function of the MscL channel and other transmembrane proteins

New Kinetic Equation for Pair-annihilating Particles: Generalization of the Boltzmann Equation

A convenient form of kinetic equation is derived for pair annihilation of heavy stable particles relevant to the dark matter problem in cosmology. The kinetic equation thus derived extends the on-shell Boltzmann equation in a most straightforward way, including the off-shell effect. A detailed balance equation for the equilibrium abundance is further analyzed. Perturbative analysis of this equation supports a previous result for the equilibrium abundance using the thermal field theory, and gives the temperature power dependence of equilibrium value at low temperatures. Estimate of the relic abundance is possible using this new equilibrium abundance in the sudden freeze-out approximation.Comment: 19 pages, LATEX file with 2 PS figure

Promotive effects of hyperthermia on the сytostatic activity to ehrlich ascites tumor cells by diverse delta-alkyllactones

To evaluate promotive effects of hyperthermia on antitumor activity of new delta-alkyllactones (DALs) of low molecular weight (184–254 Da), chemically synthesized, which are different from natural macrocyclic lactones of high molecular weight (348–439 Da), such as camptothecin and sultriecin. Methods: A suspension of Ehrlich ascites tumor (EAT) cells was mixed with a DAL in a glass tube, heated at 37 or 42 °C for 30 min in a water bath, and cultured at 37 °C for 20 or 72 h. Cell viability was measured by the mitochondrial dehydrogenase- based WST-1 assay. DALs incorporated into EAT cells was extracted and measured by gas-liquid chromatography. Results: The reduction of cell viability by DALs was markedly enhanced upon the treatment at 42 °C compared to that at 37 oC. At 37 oC, delta-hexadecalactone (DH16 : 0) and delta-tetradecalactone (DTe14 : 0) displayed cytostatic activity (at 100 µM survival level: 20.7%, 66.1%; at 50 µM — 41.2%, 82.4%, respectively). Their activity was more marked at 42 °C (at 100 µM 10.6%, 27.6%; at 50 µM 30.6, 37.5 %, ibid). The other DALs, delta-undecalactone (DU11 : 0), delta-dodecalactone (DD12 : 0), and delta-tridecanolactone (DTr13 : 0) were almost ineffective. Evaluation of survival rate in the cells treated for 30 min by DALs with the next culturing of EAT cells for 72 h resulted in the enhanced carcinostatic activity of DH16:0 and DTe14:0 even at concentrations as low as 25 µM at either 37 °C (18.5%, 78.5%, ibid) or 42 °C (5.0%, 42.0%, ibid), but the others exhibited slight activity or none. DH16 : 0 was effective at either 37 °C (36.0%) or 42 °C (23.0%) even at a lower dose of 10 µM. At the same time only the most cytostatic DH16 : 0 was incorporated into EAT cells and the rate of incorporation was more at 42 °C than at 37 °C. Conclusion: Delta-hexadecanolactone (DH16 : 0) exhibited the most cytostatic effect that was significantly enhanced by hyperthermia. It allows to consider it as a potent antitumor agent, especially in combination with hyperthermia.Цель: оценить промоторный эффект гипертермии на противоопухолевую активность новых низкомолекулярных (184–254 Да) дельта-алкиллактонов (DALs), химически синтезированных из разных макроциклических высокомолекулярных (348–439Да) лактонов естественного происхождения, таких как камптотецин и салтриецин. Методы: суспензию клеток асцитной опухоли Эрлиха (EAT) смешивали с DAL в стеклянной пробирке, нагревали до 37 °C или 42 °C в течение 30 мин на водяной бане и далее культивировали при 37 °C в течение 20 или 72 ч. Оценку жизнеспособности клеток проводили с помощью WST-1 анализа, основанного на определении митохондриальной дегидрогеназы. Инкорпорированные в EAT-клетки DALs экстрагировали, их уровень измеряли с помощью газо-жидкостной хроматографии. Результаты: DALs значительно снижали жизнеспособность клеток после предварительной обработки при 42 °C по сравнению с 37 °C. При 37 °C были эффективными дельта-гексадекалактон (DH16 : 0) и дельта-тетрадекалактон (DTe14 : 0) (при 100 μM уровень выживаемости: 20,7; 66,1%; при 50 μM — 41,2; 82,4% соответственно). Этот эффект был более выраженным при 42 °C (при 100 μM 10,6; 27,6%; при 50μM 30,6; 37,5% соответственно). Другие DALs, а именно дельта-ундекалактон (DU11 : 0), дельта-додекалактон (DD12 : 0) и дельта-тридекалактон (DTr13 : 0) были практически не эффективны. Оценка уровня выживаемости EAT-клеток, 30 мин обработанных DALs с последующим культивированием в течение 72 ч, показала повышенную канцеростатичсекую активность DH16 : 0 и DTe14 :0 даже при 25 μM концентрации, как при 37 °C (18,5; 78,5% соответсвенно), так и при 42 °C (5,0; 42,0% соответственно). Для других DALs данный эффект был незначительный либо отсутствовал. DH16 : 0 оставался эффективным как при 37 °C (36,0%), так и при 42 °C (23,0%) в 10 μM концентрации. В то же время только наиболее эффективный DAL — DH16 : 0 инкорпорировался в клетки EAT, и уровень инкорпорирования был выше при 42 °C, чем при 37 °C. Выводы: дельта-гексадеканолактон (DH16 : 0) показал наибольшую цитостатическую активность, которая значительно усиливалась в комбинации с гипертермией. Этот DAL можно рассматривать как потенциальный цитостатик, действие которого усиливается при гипертермии