Space–Time Coding for Multiuser Ultra-Wideband Communications

In this paper, we present the construction of full rate, fully diverse, and totally real space-time (ST) codes for ultra-wideband (UWB) transmissions. In particular, we construct two families of codes adapted to real carrierless UWB communications that employ pulse position modulation, pulse amplitude modulation, or a combination of the two. The first family encodes adjacent symbols and is constructed from totally real cyclic division algebras. The second family encodes the pulses used to convey one information symbol, and permits achieving high performance levels with reduced complexity. The first family of codes achieves only a fraction of the coding gain of the second one. Moreover, these coding gains are independent from the size of the transmitted constellation. For time-hopping multiple-access channels, the amplitude spreading code associated with the second family of codes is taken to be user-specific. In this case, a simple design criterion is proposed, and spreading matrices constructed according to this criterion permit reducing the level of multiple-access interference (MAI). Simulations performed over realistic indoor UWB channels verify the theoretical claims and show high performance levels and better immunity against MAI     

Top-down characterization of nucleic acids modified by structural probes using high-resolution tandem mass spectrometry and automated data interpretation

A top-down approach based on sustained off-resonance irradiation collision-induced dissociation (SORI-CID) has been implemented on an electrospray ionization (ESI) Fourier transform mass spectrometer (FTMS) to characterize nucleic acid substrates modified by structural probes. Solvent accessibility reagents, such as dimethyl sulfate (DMS), 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate (CMCT), and beta-ethoxy-alpha-ketobutyraldehyde (kethoxal, KT) are widely employed to reveal the position of single- vs double-stranded regions and obtain the footprint of bound proteins onto nucleic acids structures. Established methods require end-labeling of the nucleic acid constructs, probe-specific chemistry to produce strand cleavage at the modified nucleotides, and analysis by polyacrylamide gel electrophoresis to determine the position of the susceptible sites. However, these labor-intensive procedures can be avoided when mass spectrometry is used to identify the probe-induced modifications from their characteristic mass signatures. In particular, ESI-FTMS can be directly employed to monitor the conditions of probe application to avoid excessive alkylation, which could induce unwanted distortion or defolding of the substrate of interest. The sequence position of the covalent modifications can be subsequently obtained from classic tandem techniques, which allow for the analysis of individual target adducts present in complex reaction mixtures with no need for separation techniques. Selection and activation by SORI-CID has been employed to reveal the position of adducts in nucleic acid substrates in excess of 6 kDa. The stability of the different covalent modifications under SORI-CID conditions was investigated. Multiple stages of isolation and activation were employed in MS(n)() experiments to obtain the desired sequence information whenever the adduct stability was not particularly favorable, and SORI-CID induced the facile loss of the modified base. A new program called MS2Links was developed for the automated reduction and interpretation of fragmentation data obtained from modified nucleic acids. Based on an algorithm that searches for plausible isotopic patterns, the data reduction module is capable of discriminating legitimate signals from noise spikes of comparable intensity. The fragment identification module calculates the monoisotopic mass of ion products expected from a certain sequence and user-defined covalent modifications, which are finally matched with the signals selected by the data reduction program. Considering that MS2Links can generate similar fragment libraries for peptides and their covalent conjugates with other peptides or nucleic acids, this program provides an integrated platform for the structural investigation of protein-nucleic acid complexes based on cross-linking strategies and top-down ESI-FTMS.     

Sensitivity Analysis Methods to Design Optimal Ship Hulls

Automatic procedures for the design of ship hull geometries yielding minimal wave resistance and wave breaking are an attractive opportunity from both the economical and practical standpoints. Estimating the cost function gradient according to the Sensitivity Equation and Adjoint Methods (SEM, AM) instead of using the standard finite difference approximations has the potential of reducing the computational cost of the overall optimization procedure. Aim of this paper is to assess the actual extent of the cost reduction. Speed-up factors of up to 3.3 have been obtained in the evaluation of the cost function gradient and of about 1.6 in the overall optimization procedure applied to an optimal shape design problem of an existing tanker ship. The SEM and AM methods perform better than finite differences mainly because of (i) the smaller number of flow solutions needed to compute the cost function gradient and (ii) the opportunity of using the same LU factored matrix for both the flow solver and the SEM or AM equations, a circumstance arising as a consequence of having chosen a linearized potential flow model of the 3D free-surface problem.     

Hydroelastic optimization of a keel fin of a sailing boat: a multidisciplinary robust formulation for ship design

The paper presents a formulation for multidisciplinary design optimization of vessels, subject to uncertain operating conditions. The formulation couples the multidisciplinary design analysis with the Bayesian approach to decision problems affected by uncertainty. In the present context, the design specifications are no longer given in terms of a single operating design point, but in terms of probability density function of the operating scenario. The optimal configuration is that which maximizes the performance expectation over the uncertain parameters variation. In this sense, the optimal solution is “robust” within the stochastic scenario assumed. Theoretical and numerical issues are addressed and numerical results in the hydroelastic optimization of a keel fin of a sailing yacht are presented.     

Simultaneous removal of metals and organic compounds from a heavily polluted soil

The paper describes the results of treatment of soil samples, deriving from a dismissed industrial site, contaminated with several metals: Hg, Ni, Co, Zn, Pb, Cu, Cr, As and organic substances. The soil was subjected to remediation based on a process in which an oxidising leaching agent was produced electrochemically in-line in an undivided electrochemical cell reactor equipped with a Ti/Pt-Ir anode and a stainless steel cathode. Leaching of the soil samples was performed under dynamic conditions using a leaching column. A subsequent regeneration of the leaching solution, which consisted in electrodeposition of metals and electro-oxidation of organic substances, was carried out in a packed-bed reactor equipped with a centrally positioned graphite rod, serving as an anode, and stainless steel three-dimensional filling as a cathode. The study was focused on how and to which extent the metals present in the soil, as organic complexes, can be solubilised and how the process rates are impacted by the solution pH and other process variables. Data obtained under non-oxidising conditions, typically adopted for leaching of metals, are compared with the performance of chlorine-enriched leaching solutions. The results obtained under various conditions are also discussed in terms of the total organic carbon (TOC) removal from the water phase.     

Study of different nanostructured carbon supports for fuel cell catalysts

Pt clusters were deposited by an impregnation process on three carbon supports: multi-wall carbon nanotubes (MWNT), single-wall carbon nanohorns (SWNH), and Vulcan XC-72 carbon black to investigate the effect of the carbon support structure on the possibility of reducing Pt loading on electrodes for direct methanol (DMFC) fuel cells without impairing performance. MWNT and SWNH were in-house synthesised by a DC and an AC arc discharge process between pure graphite electrodes, respectively. UV-vis spectrophotometry, scanning and transmission electron microscopy, X-ray diffraction, and cyclic voltammetry measurements were used to characterize the Pt particles deposited on the three carbon supports. A differential yield for Pt deposition, not strictly related to the surface area of the carbon support, was observed. SWNH showed the highest surface chemical activity toward Pt deposition. Pt deposited in different forms depending on the carbon support. Electrochemical characterizations showed that the Pt nanostructures deposited on MWNT are particularly efficient in the methanol oxidation reaction.     

Presentation‐Oriented Key‐Frames Coding Based on Fractals

This paper focuses on the problem of key‐frames coding and proposes a new promising approach based on the use of fractals. The summary, made of a set of key‐frames selected from a full‐length video sequence, is coded by using a 3D fractal scheme. This allows the video presentation tool to expand the video sequence in a “natural” way by using the property of the fractals to reproduce the signal at several resolutions. This feature represents an important novelty of this work with respect to the alternative approaches, which mainly focus on the compression ratio without taking into account the presentation aspect of the video summary. In devising the coding scheme, we have taken care of the computational complexity inherent in fractal coding. Accordingly, the key‐frames are first wavelet transformed, and the fractal coding is then applied to each subband to reduce the search range. Experimental results show the effectiveness of the proposed approach.     

An application of kernel methods to gene cluster temporal meta-analysis

The application of various clustering techniques for large-scale gene-expression measurement experiments is a well-established method in bioinformatics. Clustering is also usually accompanied by functional characterization of gene sets by assessing statistical enrichments of structured vocabularies, such as the gene ontology (GO) [Gene Ontology Consortium. The gene ontology (GO) project in 2006. Nucleic Acids Research (Database issue), vol. 34; 2006. p. D322–6]. If different clusters are generated for correlated experiments, a machine learning step termed cluster meta-analysis may be performed, in order to discover relations among the components of such sets. Several approaches have been proposed: in particular, kernel methods may be used to exploit the graphical structure of typical ontologies such as GO. Following up the formulation of such approach [Merico D, Zoppis I, Antoniotti M, Mauri G. Evaluating graph kernel methods for relation discovery in GO-annotated clusters. In: KES-2007/WIRN-2007, Part IV, Lecture notes in artificial intelligence, vol. 4694. Berlin: Springer; 2007. p. 892–900; Zoppis I, Merico D, Antoniotti M, Mishra B, Mauri G. Discovering relations among GO-annotated clusters by graph kernel methods. In: Proceedings of the 2007 international symposium on bioinformatics research and applications. Lecture notes in computer science, vol. 4463. Berlin: Springer; 2007], in this paper we discuss, from an information-theoretic point of view, further results about its applicability and its performance.     

Image Analysis Techniques for Automated Hazelnut Peeling Determination

According to FAO statistics, in 2000, Italy was the second largest hazelnut (Corylus avellana, L. 1753) producer in the world. The price of the stock depends on the nut quality (kernel/nut ratio, nut and seed defect, percentage of peeling, and taste panel scores). The evaluation of peeling efficiency after toasting is generally conducted by trained operators in sight on 100 kernels. This work tests two alternative objective methods of after toasting peeling evaluation based on image analysis. Eleven hazelnut cultivars were analyzed and results were compared with the ones assessed by trained operators. Images were analyzed with two statistical approaches: fixed values of RGB thresholding and trained K Nearest Neighbors (KNN). Root mean squared error (RMSE), estimating the comparison between operators and the two image analysis-based techniques, shows better results for KNN (6.6) with respect to fixed threshold (15.9).     

Numerical Simulation of Electromagnetic Solitons and Their Interaction with Matter

A suitable correction of the Maxwell model brings to an enlargement of the space of solutions, allowing for the existence of solitons in vacuum. We review the basic achievements of the theory and discuss some approximation results based on an explicit finite-difference technique. The experiments in two dimensions simulate travelling solitary electromagnetic waves, and show their interaction with conductive walls. In particular, the classical dispersion, exhibited by the passage of a photon through a small aperture, is examined.