Fluctuation Cumulant Behavior for the Field-Pulse Induced Magnetisation-Reversal Transition in Ising Models

The universality class of the dynamic magnetisation-reversal transition, induced by a competing field pulse, in an Ising model on a square lattice, below its static ordering temperature, is studied here using Monte Carlo simulations. Fourth order cumulant of the order parameter distribution is studied for different system sizes around the phase boundary region. The crossing point of the cumulant (for different system sizes) gives the transition point and the value of the cumulant at the transition point indicates the universality class of the transition. The cumulant value at the crossing point for low temperature and pulse width range is observed to be significantly less than that for the static transition in the same two-dimensional Ising model. The finite size scaling behaviour in this range also indicates a higher correlation length exponent value. For higher temperature and pulse width range, the transition seems to fall in a mean-field like universality class.Comment: 5 pages, 8 eps figures, thoroughly revised manuscript with new figures, accepted in Phys. Rev. E (2003

Kolkata Restaurant Problem as a generalised El Farol Bar Problem

Generalisation of the El Farol bar problem to that of many bars here leads to the Kolkata restaurant problem, where the decision to go to any restaurant or not is much simpler (depending on the previous experience of course, as in the El Farol bar problem). This generalised problem can be exactly analysed in some limiting cases discussed here. The fluctuation in the restaurant service can be shown to have precisely an inverse cubic behavior, as widely seen in the stock market fluctuations.Comment: 2 column RevTeX4, 4 pages, 3 eps figs; to be published in 'Econophysics of Markets and Business Networks', [Proc. Econophys-Kolkata III], Eds. A. Chatterjee, B. K. Chakrabarti, New Economic Windows Series, Springer, Milan, 2007, pp. 220-22

Length and time scale divergences at the magnetization-reversal transition in the Ising model

The divergences of both the length and time scales, at the magnetization- reversal transition in Ising model under a pulsed field, have been studied in the linearized limit of the mean field theory. Both length and time scales are shown to diverge at the transition point and it has been checked that the nature of the time scale divergence agrees well with the result obtained from the numerical solution of the mean field equation of motion. Similar growths in length and time scales are also observed, as one approaches the transition point, using Monte Carlo simulations. However, these are not of the same nature as the mean field case. Nucleation theory provides a qualitative argument which explains the nature of the time scale growth. To study the nature of growth of the characteristic length scale, we have looked at the cluster size distribution of the reversed spin domains and defined a pseudo-correlation length which has been observed to grow at the phase boundary of the transition.Comment: 9 pages Latex, 3 postscript figure

Characterizations of an ecotype of brake-fern, Pteris vittata, for arsenic tolerance and accumulation in plant biomass

An ecotype of brake fern (Pteris vittata) was assessed for arsenic tolerance and accumulation in its biomass under in vivo and in vitro condition; using soil, and agargelled Murashige and Skoog (MS) medium supplemented with different concentrations of arsenic. The plants were raised in soil amended with 100–1000 mg arsenic kg^–1 soil, and MS medium was supplemented with 10–300 mg arsenic L–1 medium using Na2HAsO4×7H2O. The spores and haploid gametophytic-prothalli were raised in vitro on MS medium supplemented with arsenic. The field plants showed normal growth and biomass formation in arsenic amended soil, and accumulated 1908– 4700 mg arsenic kg^–1 dry aerial biomass after 10 weeks of growth. Arsenic toxicity was observed above >200 mg arsenic kg^–1 soil. The concentrations of arsenic accumulated in the plant biomass were statistically significant (p < 0.05). Normal plants were developed from spores and gametophyte prothalli on the MS media supplemented with 50–200 mg arsenic L^–1 medium. The in vitro raised plants were tolerant to 300 mg arsenic kg^–1 of soil and accumulated up to 3232 mg arsenic kg^–1 dry aerial biomass that showed better growth performance, biomass generation and arsenic accumulation in comparison to the field plants.Екотип птериса стрічкового (Pteris vittаta) був досліджений на стійкість до миш’яку та його накопичення в біомасі в умовах in vivo і in vitro з використанням грунту та агаризованого середовища МурасігеСкуга (MS), що містять миш’як в різних концентраціях. Рослини вирощували на грунті, що містить 100–1000 мг миш’яку на 1 кг грунту, чи в грунті Мурасіге-Скуга, в котрий додавали 10–300 мг/л Na2HAsO4 ×7H2O. Спори та гаплоїдні гематофітні паростки росли in vitro на середовищі MS з миш’яком. Рослини, які ростуть на грунті, що містить миш’як, характеризувались нормальним ростом і накопиченням біомаси та через 10 тижнів вирощування накопичували 1908–4700 миш’яку на 1 кг сухої надземної біомаси. Токсичність миш’яку проявлялась при його концентрації в грунті більше 200 мг/кг. Концентрації миш’яку, котрі накопичувалися в рослинній біомасі, були статистично значимими (р < 0.5). Зі спор та гаметофітних паростків, котрі вирощували на грунті MS з 50–200 мг/л миш’яку, розвивались нормальні рослини. Отримані in vitro рослини були стійкими до миш’яку в концентрації 300 мг/кг грунту та накопичували миш’як до 3232 мг/кг сухої надземної біомаси, що означає покращання ростових характеристик, формування біомаси та накопичення миш’яку в порівнянні з рослинами, вирощеними на полі.Экотип птериса ленточного (Pteris vittаta) был исследован на устойчивость к мышьяку и его накопление в биомассе в условиях in vivo и in vitro с использованием почвы и агаризованной среды Мурасиге-Скуга (MS), содержащих мышьяк в разных концентрациях. Растения выращивали в почве, содержащей 100–1000 мг мышьяка на 1 кг почвы, или в среде Мурасиге-Скуга, в которую добавляли 10–300 мг/л Na2HAsO4 × 7H2O. Споры и гаплоидные гаметофитные проростки росли in vitro на среде MS с мышьяком. Растения, которые росли в почве, содержащей мышьяк, характеризовались нормальным ростом и накоплением биомассы и через 10 недель выращивания накапливали 1908–4700 мг мышьяка на 1 кг сухой надземной биомассы. Токсичность мышьяка проявлялась при его концентрации в почве свыше 200 мг/кг. Концентрации мышьяка, которые накапливались в растительной биомассе, были статистически значимыми (р < 0,5). Из спор и гаметофитных проростков, которые выращивали на среде MS с 50–200 мг/л мышьяка, развивались нормальные растения. Полученные in vitro растения были устойчивы к мышьяку в концентрации 300 мг/кг почвы и накапливали мышьяк до 3232 мг/кг сухой надземной биомассы, что означает улучшенные ростовые характеристики, формирование биомассы и накопление мышьяка по сравнению с растениями, выращенными в поле

Scale-free network on a vertical plane

A scale-free network is grown in the Euclidean space with a global directional bias. On a vertical plane, nodes are introduced at unit rate at randomly selected points and a node is allowed to be connected only to the subset of nodes which are below it using the attachment probability: $\pi_i(t) \sim k_i(t)\ell^{\alpha}$. Our numerical results indicate that the directed scale-free network for $\alpha=0$ belongs to a different universality class compared to the isotropic scale-free network. For $\alpha < \alpha_c$ the degree distribution is stretched exponential in general which takes a pure exponential form in the limit of $\alpha \to -\infty$. The link length distribution is calculated analytically for all values of $\alpha$.Comment: 4 pages, 4 figure

Stationary State Solutions of a Bond Diluted Kinetic Ising Model: An Effective-Field Theory Analysis

We have examined the stationary state solutions of a bond diluted kinetic Ising model under a time dependent oscillating magnetic field within the effective-field theory (EFT) for a honeycomb lattice $(q=3)$. Time evolution of the system has been modeled with a formalism of master equation. The effects of the bond dilution, as well as the frequency $(\omega)$ and amplitude $(h/J)$ of the external field on the dynamic phase diagrams have been discussed in detail. We have found that the system exhibits the first order phase transition with a dynamic tricritical point (DTCP) at low temperature and high amplitude regions, in contrast to the previously published results for the pure case \cite{Ling}. Bond dilution process on the kinetic Ising model gives rise to a number of interesting and unusual phenomena such as reentrant phenomena and has a tendency to destruct the first-order transitions and the DTCP. Moreover, we have investigated the variation of the bond percolation threshold as functions of the amplitude and frequency of the oscillating field.Comment: 8 pages, 4 figure

Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notablesuccesses in some cancers; however, significant problems remain with this approach. Many targetedtherapies are highly toxic, costs are extremely high, and most patients experience relapse after a fewdisease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistantimmortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are notreliant upon the same mechanisms as those which have been targeted). To address these limitations, aninternational task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspectsof relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a widerange of high-priority targets (74 in total) that could be modified to improve patient outcomes. For thesetargets, corresponding low-toxicity therapeutic approaches were then suggested, many of which werephytochemicals. Proposed actions on each target and all of the approaches were further reviewed forknown effects on other hallmark areas and the tumor microenvironment. Potential contrary or procar-cinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixedevidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of therelationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. Thisnovel approach has potential to be relatively inexpensive, it should help us address stages and types ofcancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for futureresearch is offered

Comments by B.K. Chakrabarti on the Visioneer white papers by D. Helbing and S. Balietti

This article comments on the Visioneer (Envisioning a Socio- Economic Knowledge Collider) Project as described in the following white papers [1–3]

Multivariable optimization: Quantum annealing and computation

Recent developments in quantum annealing techniques have been indicating potential advantage of quantum annealing for solving NP-hard optimization problems. In this article we briefly indicate and discuss the beneficial features of quantum annealing techniques and compare them with those of simulated annealing techniques. We then briefly discuss the quantum annealing studies of some model spin glass and kinetically constrained systems