Detection of lead in Zea mays by dual‐energy X‐ray microtomography at the SYRMEP beamline of the ELETTRA synchrotron and by atomic absorption spectroscopy

This study is related to the application of the X‐ray dual‐energy microradiography technique together with the atomic absorption spectroscopy (AAS) for the detection of lead on Zea mays stem, ear, root, and leaf samples. To highlight the places with lead intake, the planar radiographs taken with monochromatic X‐ray radiation in absorption regime with photon energy below and above the absorption edge of a given chemical element, respectively, are analyzed and processed. To recognize the biological structures involved in the intake, the dual‐energy images with the lead signal have been compared with the optical images of the same Z. mays stem. The ear, stem, root, and leaf samples have also been analyzed with the AAS technique to measure the exact amount of the hyperaccumulated lead. The AAS measurement revealed that the highest intake occurred in the roots while the lowest in the maize ears and in the leaf. It seems there is a particular mechanism that protects the seeds and the leaves in the intake process. Microsc. Res. Tech., 2010. © 2009 Wiley‐Liss, Inc. This article was published online on 1 December 2009. An error was subsequently identified. This notice is included in the online and print version to indicate that both have been corrected 19 February 2010.     

Healing DNA Self-Assemblies Using Punctures

In self-assembly, individual components (commonly referred to as tiles) have sufficient infor mation to build templates for structures such as lat tices for two-dimensional scaffolds. Tile sets that can heal (fully or partially) an erroneous DNA assembly have been proposed. Healing requires growth to be restarted such that erroneous tiles can be removed and the correct tiles can bind to the aggregate. Punctures have been proposed for this purpose; in this paper, a puncture is intentionally induced in the self-assembly to restart the growth process. The goal of this paper is to characterize an intentionally induced puncture (and its relevant properties) on an erroneous tile site in the grown crystal as part of a healing process. This allows to propagate any newly generated error away from the source of growth (i.e. the seed tile), such that self-assembly can continue along specific directions. Different types of puncture are considered with respect to healing and related features, such as growth direction, error and aggregate types. Punctures are analyzed using a new characterization and metric; different tile sets are investigated in detail for healing of a DNA self-assembly.

CMOS-Compatible Room-Temperature Rectifier Toward Terahertz Radiation Detection

In this paper, we present a new rectifying device, compatible with the technology of CMOS image sensors, suitable for implementing a direct-conversion detector operating at room temperature for operation at up to terahertz frequencies. The rectifying device can be obtained by introducing some simple modifications of the charge-storage well in conventional CMOS integrated circuits, making the proposed solution easy to integrate with the existing imaging systems. The rectifying device is combined with the different elements of the detector, composed of a 3D high-performance antenna and a charge-storage well. In particular, its position just below the edge of the 3D antenna takes maximum advantage of the high electric field concentrated by the antenna itself. In addition, the proposed structure ensures the integrity of the charge-storage well of the detector. In the structure, it is not necessary to use very scaled and costly technological nodes, since the CMOS transistor only provides the necessary integrated readout electronics. On-wafer measurements of RF characteristics of the designed junction are reported and discussed. The overall performances of the entire detector in terms of noise equivalent power (NEP) are evaluated by combining low-frequency measurements of the rectifier with numerical simulations of the 3D antenna and the semiconductor structure at 1 THz, allowing prediction of the achievable NEP.     

Self‐Immobilizing Precatalysts: Norbornene‐Bridged Zirconium ansa‐Metallocenes

We report here the synthesis of new tethered biscyclopentadienyl and bisindenyl zirconocenes, bearing one unsaturation on the interannular bridge, and their use as self‐immobilizing catalysts. They proved to be active catalysts towards ethylene polymerization in solution, with activities comparable to those displayed by commercial rac‐Et(Ind)₂ZrCl₂. When tested as self‐polymerization catalysts under suitable experimental conditions, they gave colored precipitates that, once reactivated with MAO, were significantly active in ethylene polymerization, although lower than those of the corresponding catalytic systems in solution. The molecular weights of the produced polymers were similar to those obtained with the same catalysts in solution, but their distribution resulted to be broader, with values typical of heterogeneous catalytic systems. From ¹³C NMR studies we had the first spectroscopic evidence of the actual incorporation of a metallocene of this type into a polymeric chain.     

A Novel Approach to Fiber-Optic Tweezers: Numerical Analysis of the Trapping Efficiency

We present a novel all-fiber optical tweezer (OT) for biological applications. The tweezer is based on a new approach relying on total internal reflection in an annular core fiber or into a fiber bundle. The proposed device, whose trapping efficacy has been recently demonstrated experimentally, is extremely promising, also because optical manipulation and analysis functions can be easily added to the tweezer basic structure, leading to the realization of a powerful biotool. In this paper, a detailed numerical analysis of the structure properties and of its efficiency is carried out in the Mie regime. Moreover, by defining a new parameter to evaluate the trapping efficiency, we perform a comparison between the proposed tweezer structure and a standard OT based on a strongly focused Gaussian beam.     

Effects of scattering resonances on carrier-carrier entanglement in charged quantum dots

We address the problem of the entanglement generation in an electron-scattering by a 1D double-barrier resonant tunnelling device. In particular we analyze the role played by transport resonances in the appearance of quantum correlations between the energy states of the electrons. The entanglement is not sensitive to the presence of Breit-Wigner resonances, while it may be controlled by manipulating Fano resonances. Such a behavior is ascribed to the different mechanisms characterizing the two types of processes.     

Solving unit commitment problems with general ramp constraints

Lagrangian relaxation (LR) algorithms are among the most successful approaches for solving large-scale hydro-thermal unit commitment (UC) problems; this is largely due to the fact that the single-unit commitment (1UC) problems resulting from the decomposition, incorporating many kinds of technical constraints such as minimum up- and down-time requirements and time-dependent startup costs, can be efficiently solved by dynamic programming (DP) techniques. Ramp constraints have historically eluded efficient exact DP approaches; however, this has recently changed [Frangioni A, Gentile C. Solving nonlinear single-unit commitment problems with ramping constraints. Oper Res 2006;54(4):767–75]. We show that the newly proposed DP algorithm for ramp-constrained (1UC) problems allows to extend existing LR approaches to ramp-constrained (UC); this is not obvious since the heuristic procedures typically used to recover a primal feasible solution are not easily extended to take ramp limits into account. However, dealing with ramp constraints in the subproblems turns out to be sufficient to provide the LR heuristic enough guidance to produce good feasible solutions even with no other modification of the approach; this is due to the fact that (sophisticated) LR algorithms to (UC) duly exploit the primal information computed by the Lagrangian Dual, which in the proposed approach is ramp feasible. We also show by computational experiments that the LR [approach] is competitive with those based on general-purpose mixed-integer program (MIP) solvers for large-scale instances, especially hydro-thermal ones.     

Plant Growth Promotion Function of Bacillus sp. Strains Isolated from Salt-Pan Rhizosphere and Their Biocontrol Potential against Macrophomina phaseolina

In recent decades, intensive crop management has involved excessive use of pesticides or fertilizers, compromising environmental integrity and public health. Accordingly, there has been worldwide pressure to find an eco-friendly and safe strategy to ensure agricultural productivity. Among alternative approaches, Plant Growth-Promoting (PGP) rhizobacteria are receiving increasing attention as suitable biocontrol agents against agricultural pests. In the present study, 22 spore-forming bacteria were selected among a salt-pan rhizobacteria collection for their PGP traits and their antagonistic activity against the plant pathogen fungus Macrophomina phaseolina. Based on the higher antifungal activity, strain RHFS10, identified as Bacillus vallismortis, was further examined and cell-free supernatant assays, column purification, and tandem mass spectrometry were employed to purify and preliminarily identify the antifungal metabolites. Interestingly, the minimum inhibitory concentration assessed for the fractions active against M. phaseolina was 10 times lower and more stable than the one estimated for the commercial fungicide pentachloronitrobenzene. These results suggest the use of B. vallismortis strain RHFS10 as a potential plant growth-promoting rhizobacteria as an alternative to chemical pesticides to efficiently control the phytopathogenic fungus M. phaseolina.