Efficiency of naphthalene biodegradation by Pseudomonas putida G7 in soil

The efficiency of naphthalene degradation by Pseudomonas putida G7 in soil was assessed using a mathematical model. The number of microorganisms and the concentration of naphthalene in soil samples were monitored. The feasibility of a spectrofluorometric method for naphthalene assay in soil samples was compared with high pressure liquid chromatography. A proposed mathematical model described the growth of the naphthalene‐degrading strains and the consumption of substrates (naphthalene, naphthalene degradation intermediates and soil organic substances) in soil. To describe the growth kinetics of microorganisms having high affinity to substrates with low solubility, two differential equations with substrate exponent 2/3 were proposed. These equations were used to describe utilization of soil organic matter. The model parameters characterize the growth rates for different substrates and respective yield coefficients, specific bacterial death and adaptation rates, and also the rates of PAHs degradation and evaporation. These characteristics can be used in choosing the bacterial strains for biopreparations and efficient clean‐up biotechnology of polluted soils. Copyright © 2004 Society of Chemical Industry     

Standby supply voltage minimization for deep sub-micron SRAM

Suppressing the leakage current in memories is critical in low-power design. By reducing the standby supply voltage (V_DD) to its limit, which is the data retention voltage (DRV), leakage power can be substantially reduced. This paper models the DRV of a standard low leakage SRAM module as a function of process and design parameters, and analyzes the SRAM cell stability when V_DD approaches DRV. The DRV model is verified using simulations as well as measurements from a 4 KB SRAM chip in a 0.13 μm technology. Due to a large on-chip variation, DRV of the 4 KB SRAM module ranges between 60 and 390 mV. Measurements taken at 100 mV above the worst-case DRV show that reducing the SRAM standby V_DD to a safe level of 490 mV saves 85% leakage power. Further savings can be achieved by applying DRV-aware SRAM optimization techniques, which are discussed at the end of this paper.     

Securing interaction between threads and the scheduler in the presence of synchronization

The problem of information flow in multithreaded programs remains an important open challenge. Existing approaches to specifying and enforcing information-flow security often suffer from over-restrictiveness, relying on nonstandard semantics, lack of compositionality, inability to handle dynamic threads, inability to handle synchronization, scheduler dependence, and efficiency overhead for the code that results from security-enforcing transformations. This paper suggests a remedy for some of these shortcomings by developing a novel treatment of the interaction between threads and the scheduler. As a result, we present a permissive noninterference-like security specification and a compositional security type system that provably enforces this specification. The type system guarantees security for a wide class of schedulers and provides a flexible and efficiency-friendly treatment of dynamic threads.     

Energy Levels of “Hydrogen Atom” in Discrete Time Dynamics

We analyze dynamical consequences of a conjecture that there exists a fundamental (indivisible) quant of time. In particular we study the problem of discrete energy levels of hydrogen atom. We are able to reconstruct potential which in discrete time formalism leads to energy levels of unperturbed hydrogen atom. We also consider linear energy levels of quantum harmonic oscillator and show how they are produced in the discrete time formalism. More generally, we show that in discrete time formalism finite motion in central potential leads to discrete energy spectrum, the property which is common for quantum mechanical theory. Thus deterministic (but discrete time!) dynamics is compatible with discrete energy levels.     

The Absence of a Shape Bias in Children's Word Learning.

There is debate about whether preschool-age children interpret words as referring to kinds or to classes defined by shape similarity. The authors argue that the shape bias reported in previous studies is a task-induced artifact rather than a genuine word-learning strategy. In particular, children were forced to extend an object's novel label to one of several stand-alone, simple-shaped items, including a same-shape option from a different category and a different-shape option from the same superordinate category. Across 6 experiments, the authors found that the shape bias was eliminated (a) when the objects were more complex, (b) when they were presented in context, or (c) when children were no longer forced to choose. Moreover, children preferred the different-shape category alternatives when these were part of the same basic-level category as the target. The present experiments suggest that children seek out objects of the same kind when presented with a novel label, even if they are sometimes unable to identify the relevant kinds on their own. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Properties of anodic oxides grown on a hafnium–tantalum–titanium thin film library

A ternary thin film combinatorial materials library of the valve metal system Hf–Ta–Ti obtained by co-sputtering was studied. The microstructural and crystallographic analysis of the obtained compositions revealed a crystalline and textured surface, with the exception of compositions with Ta concentration above 48 at.% which are amorphous and show a flat surface. Electrochemical anodization of the composition spread thin films was used for analysing the growth of the mixed surface oxides. Oxide formation factors, obtained from the potentiodynamic anodization curves, as well as the dielectric constants and electrical resistances, obtained from electrochemical impedance spectroscopy, were mapped along two dimensions of the library using a scanning droplet cell microscope. The semiconducting properties of the anodic oxides were mapped using Mott–Schottky analysis. The degree of oxide mixing was analysed qualitatively using x-ray photoelectron spectroscopy depth profiling. A quantitative analysis of the surface oxides was performed and correlated to the as-deposited metal thin film compositions. In the concurrent transport of the three metal cations during oxide growth a clear speed order of Ti > Hf > Ta was proven.     

Interactions and Chemical Transformations of Coronene Inside and Outside Carbon Nanotubes

By exposing flat and curved carbon surfaces to coronene, a variety of van der Waals hybrid heterostructures are prepared, including coronene encapsulated in carbon nanotubes, and coronene and dicoronylene adsorbed on nanotubes or graphite via π–π interactions. The structure of the final product is determined by the temperature of the experiment and the curvature of the carbon surface. While at temperatures below and close to the sublimation point of coronene, nanotubes with suitable diameters are filled with single coronene molecules, at higher temperatures additional dimerization and oligomerization of coronene occurs on the surface of carbon nanotubes. The fact that dicoronylene and possible higher oligomers are formed at lower temperatures than expected for vapor‐phase polymerization indicates the active role of the carbon surface used primarily as template. Removal of adsorbed species from the nanotube surface is of utmost importance for reliable characterization of encapsulated molecules: it is demonstrated that the green fluorescence attributed previously to encapsulated coronene is instead caused by dicoronylene adsorbed on the surface which can be solubilized and removed using surfactants. After removing most of the adsorbed layer, a combination of Raman spectroscopy and transmission electron microscopy was employed to follow the transformation dynamics of coronene molecules inside nanotubes.     

Directed 2D-to-3D pattern transfer method for controlled fabrication of topologically complex 3D features in silicon

A process that allows control over the 3D motion of catalyst nanostructures during metal-assisted chemical etching by their local pinning prior to etching is demonstrated. The pinning material acts as a fulcrum for rotation of the catalyst structures resulting in etching of silicon features with rotational geometry.