Modeling and biological investigations of an unusual behavior of novel synthesized acridine-based polyamine ligands in the binding of double helix and G-quadruplex DNA

Three novel 2,7-substituted acridine derivatives were designed and synthesized to investigate the effect of this functionalization on their interaction with double-stranded and G-quadruplex DNA. Detailed investigations of their ability to bind both forms of DNA were carried out by using spectrophotometric, electrophoretic, and computational approaches. The ligands in this study are characterized by an open-chain (L1) or a macrocyclic (L2, L3) framework. The aliphatic amine groups in the macrocycles are joined by ethylene (L2) or propylene chains (L3). L1 behaved similarly to the lead compound m-AMSA, efficiently intercalating into dsDNA, but stabilizing G-quadruplex structures poorly, probably due to the modest stabilization effect exerted by its protonated polyamine chains. L2 and L3, containing small polyamine macrocyclic frameworks, are known to adopt a rather bent and rigid conformation; thus they are generally expected to be sterically impeded from recognizing dsDNA according to an intercalative binding mode. This was confirmed to be true for L3. Nevertheless, we show that L2 can give rise to efficient π-π and H-bonding interactions with dsDNA. Additionally, stacking interactions allowed L2 to stabilize the G-quadruplex structure: using the human telomeric sequence, we observed the preferential induction of tetrameric G-quadruplex forms. Thus, the presence of short ethylene spacers seems to be essential for obtaining a correct match between the binding sites of L2 and the nucleobases on both DNA forms investigated. Furthermore, current modeling methodologies, including docking and MD simulations and free energy calculations, provide structural evidence of an interaction mode for L2 that is different from that of L3; this could explain the unusual stabilizing ability of the ligands (L2>L3>L1) toward G-quadruplex that was observed in this study.     

Measurement of ultimate tensile strength and Young modulus in LYSO scintillating crystals

Scintillating crystals are employed in high energy physics, in medical imaging, diagnostic and security. Two mechanical properties of lutetium-yttrium oxyorthosilicate cerium-doped Lu_2(1−x)Y_2xSiO₅:Ce with x=0.1 (LYSO) crystals have been measured: the ultimate tensile stress (σ_UTS) and the Young elastic modulus (E). Measurements are made by means of a 4-points loading device and the experimental results account for an elastic-brittle stress-strain relation, which depends heavily on the specimen preparation and the material defects. σ_UTS along the [0 1 0] tensile direction ranges within 68.14 and 115.61 MPa, which, in the lowest case, is more than twice with respect to those measured for PbWO₄ (PWO), exhibiting a marked difference between the annealed and the not-annealed samples. The mean elastic modulus (E), along the same direction, is E=1.80×10¹¹ (±2.15×10¹⁰) N/m², with lower dispersion respect to UTS data. This type of analysis and study can be included into quality control procedures of crystals, based on samples taken out of production; such procedures can be established for industrial processing of crystals aimed to the high energy physics (calorimeters) and medical imaging (PET, etc.) applications.     

Integrating load balancing and locality in the parallelization of irregular problems

An irregular problem models the evolution of a system where several elements are irregularly distributed in a domain. The evolution modifies this distribution in a way that cannot be foreseen and the behavior of each element depends upon the elements close to it according to a problem dependent relation. Starting from a hierarchical representation of the domain, we define a parallelization methodology that includes a load balancing strategy that preserves this locality property and a strategy to collect information distributed onto the processing nodes.     

Characterization of human skin impedance after electrical treatment for transdermal drug delivery

A measurement technique based on Electrical Impedance Spectroscopy (EIS) aimed at discriminating electrical effects of the electrical treatment from the electrical characteristics of drug delivery in human skin is presented. The technique turns out to be useful as the first and most crucial step in determining the drug delivered into the skin after electrical treatment. After recalling the background of electrical measurements principle and electrical modeling of biological tissues, the proposed measurement procedure is illustrated. Then, experimental tests of in vivo characterization of the procedure are reported, and the obtained results are discussed.     

Lower bounds on the rotation distance of binary trees

The rotation distanced(S,T) between two binary trees S, T of n vertices is the minimum number of rotations to transform S into T. While it is known that d(S,T)?2n−6, a well-known conjecture states that there are trees for which this bound is sharp for any value of n?11. We are unable to prove the conjecture, but we give here some simple criteria for lower bound evaluation, leading for example to individuate some “regular” tree structures for which d(S,T)=3n/2−O(1), or d(S,T)=5n/3−O(1).     

A decentralized kinematic control architecture for collaborative and cooperative multi-arm systems

In this paper a two-layer decentralized framework for kinematic control of cooperative and collaborative multi-robot systems is developed. The motion of the system is specified at the workpiece level, by adopting a task-oriented formulation for cooperative tasks. The first layer computes the motion of the single arms in the system. In detail, the control unit of each robot computes the end-effector motion references in a decentralized fashion on the basis of the knowledge of the assigned cooperative task and the motion references computed by its neighbors. Then, in the second layer, each control unit computes the reference joint motion of the corresponding manipulator from the end-effector reference motion. The approach is, then, tested in simulation on a work-cell composed by several manipulators, and experimentally on a dual-arm kinematically redundant work-cell composed by industrial manipulators.     

Planar packing of trees and spider trees

In [A. García, C. Hernando, F. Hurtado, M. Noy, J. Tejel, Packing trees into planar graphs, J. Graph Theory (2002) 172-181] García et al. conjectured that for every two non-star trees there exists a planar graph containing them as edge-disjoint subgraphs. In this paper we prove the conjecture in the case in which one of the trees is a spider tree.     

SVD-Based Techniques for Zero-Padded Block Transmission Over Fading Channels

In this paper, the performance of filter bank transceivers in the presence of a dispersive time-variant channel is investigated. It is well known that filter bank transceivers can be adapted to the channel transfer function to yield intersymbol interference (ISI) cancellation. When the channel is time variant, several problems arise, since the transceiver should be changed whenever the channel evolves. In this paper, we will allow both the transmitter and the receiver to change and satisfy the interference-free condition, under the assumption of a zero-padded block transmission. In this case, the optimum transmitter-receiver pair can be computed by using a singular value decomposition (SVD) of the channel matrix. A fast receiver adaptation based on SVD tracking is presented. Simulation results show that minimum performance loss with respect to the optimum receiver can be achieved for our reduced complexity receiver