Magneto-impedance of glass-coated Fe-Ni-Cu microwires

The magneto-impedance (MI) of glass-coated Fe-Ni-Cu microwires was investigated for longitudinal radio-frequency (RF) currents up to a frequency of 200 MHz using an RF lock-in amplifier method. The MI, defined as DZ/Z = [Z(H)-Z(H=0.3T)]/Z(H=0.3T), displays a peak structure (negative MI) at zero field for RF currents with frequencies less than 20MHz and this crosses over to a sharp dip (positive MI) at higher frequencies. This crossover behavior is ascribed to the skin-depth-limited response primarily governed by the field-dependence of the permeability. Large saturation fields (300 to 600 Oe) and other anomalies indicate the possible influence of giant magneto-resistance (GMR) on the MI.Comment: 3 pages, 2-column, 3 figures. To be published in J. Appl. Phys. 2000 (44th MMM conference proceedings

Dynamical epidemic suppression using stochastic prediction and control

We consider the effects of noise on a model of epidemic outbreaks, where the outbreaks appear. randomly. Using a constructive transition approach that predicts large outbreaks, prior to their occurrence, we derive an adaptive control. scheme that prevents large outbreaks from occurring. The theory inapplicable to a wide range of stochastic processes with underlying deterministic structure.Comment: 14 pages, 6 figure

Regression of murine lung tumors by the let-7 microRNA.

MicroRNAs (miRNAs) have recently emerged as an important new class of cellular regulators that control various cellular processes and are implicated in human diseases, including cancer. Here, we show that loss of let-7 function enhances lung tumor formation in vivo, strongly supporting the hypothesis that let-7 is a tumor suppressor. Moreover, we report that exogenous delivery of let-7 to established tumors in mouse models of non-small-cell lung cancer (NSCLC) significantly reduces the tumor burden. These results demonstrate the therapeutic potential of let-7 in NSCLC and point to miRNA replacement therapy as a promising approach in cancer treatment

Internal displacement reactions in multicomponent oxides: Part II. Oxide solid solutions of wide composition range

As models of internal displacement reactions in oxide solid solutions, the following reactions were studied at 1273 K as a function of time: Fe + NixMg1-x)O = Ni + (FexMg1-x)O Fe + (Co0.5Mg0.5)O = Co + (Fe0.5Mg0.5)O In both reactions, Ni or Co in the starting oxide is displaced by Fe and the γ-(Ni-Fe) or (Co-Fe) alloy is precipitated. In the reaction zone, composition gradients develop in both product phases, viz., the oxide and the alloy precipitate. The Ni (or Co) concentration of the alloy precipitate increases towards the reaction front. In the product oxide, the "inert" Mg diffuses toward the reaction front along with the Fe, while the Ni (or Co) diffusion is in the opposite direction, towards the Fe/boundary. The shape of the composition profiles for Mg and Fe in the product oxide suggests that cross-coefficient terms in the generalized flux equations contribute significantly to the cation flux. The parabolic rate constants of reactions involving Fe/(NixMg1-x)O decrease by nearly four orders of magnitude when x decreases from 1 to 0.1

The role of body rotation in bacterial flagellar bundling

In bacterial chemotaxis, E. coli cells drift up chemical gradients by a series of runs and tumbles. Runs are periods of directed swimming, and tumbles are abrupt changes in swimming direction. Near the beginning of each run, the rotating helical flagellar filaments which propel the cell form a bundle. Using resistive-force theory, we show that the counter-rotation of the cell body necessary for torque balance is sufficient to wrap the filaments into a bundle, even in the absence of the swirling flows produced by each individual filament

Internal displacement reactions in multicomponent oxides. Part I. Line compounds with narrow homogeneity range

As a model of an internal displacement reaction involving a ternary oxide "line" compound, the following reaction was studied at 1273 K as a function of time, t: Fe + NiTiO3 = "Ni" + "FeTiO3" Both polycrystalline and single-crystal materials were used as the starting NiTiO3 oxide. During the reaction, the Ni in the oxide compound is displaced by Fe and it precipitates as a γ-(Ni-Fe) alloy. The reaction preserves the starting ilmenite structure. The product oxide has a constant Ti concentration across the reaction zone, with variation in the concentration of Fe and Ni, consistent with ilmenite composition. In the case of single-crystal NiTiO3 as the starting oxide, the γ alloy has a "layered" structure and the layer separation is suggestive of Liesegang-type precipitation. In the case of polycrystalline NiTiO3 as the starting oxide, the alloy precipitates mainly along grain boundaries, with some particles inside the grains. A concentration gradient exists in the alloy across the reaction zone and the composition is >95 at. pct Ni at the reaction front. The parabolic rate constant for the reaction is kp = 1.3 × 10-12 m2 s-1 and is nearly the same for both single-crystal and polycrystalline oxides

Discrete Dynamical Systems Embedded in Cantor Sets

While the notion of chaos is well established for dynamical systems on manifolds, it is not so for dynamical systems over discrete spaces with $N$ variables, as binary neural networks and cellular automata. The main difficulty is the choice of a suitable topology to study the limit $N\to\infty$. By embedding the discrete phase space into a Cantor set we provided a natural setting to define topological entropy and Lyapunov exponents through the concept of error-profile. We made explicit calculations both numerical and analytic for well known discrete dynamical models.Comment: 36 pages, 13 figures: minor text amendments in places, time running top to bottom in figures, to appear in J. Math. Phy