One-pot TiO2-catalyzed synthesis of nucleic bases and acyclonucleosides from formamide: implications for the origin of life

A novel one-pot TiO2-catalyzed synthesis of nucleobases and acyclonucleosides from formamide is reported. Since formamide can be formed under prebiotic conditions, these reactions have implications for the origin of life. While a number of purine derivatives have been found as products of non-TiO2-catalyzed reactions, important compounds that would not otherwise occur (namely, thymine, 5-hydroxymethyluracil, and acyclonucleosides) are formed in acceptable yields by TiO2-catalyzed reactions. Moreover, TiO2 selectively affects the rates of degradation of nucleobases, as single units and when embedded in polynucleotides.     

Structural reliability assessment of cracked pipes: The role of probability of detection data

The structural reliability of industrial pipes, including those in the nuclear, oil, and gas industries, has a significant impact on the safety of people and the environment. This work aims to develop a computational structural reliability model method in conjunction with the failure assessment diagram method and the user‐defined probability of detection curves of non‐destructive testing are used. The concept of “reliability factor of a repair” is proposed. Then, the effects of the pipe inspection considering different user‐defined probability of detection curves and different values of the reliability factor of a repair on probability of failure are discussed. The main results include the identification of cases where performing repairs do not guarantee an improved reliability, as well as the consequences of considering the repair as a “perfect process” which result in non‐conservative assessments.     

Neural projection techniques for the visual inspection of network traffic

A crucial aspect in network monitoring for security purposes is the visual inspection of the traffic pattern, mainly aimed to provide the network manager with a synthetic and intuitive representation of the current situation. Towards that end, neural projection techniques can map high-dimensional data into a low-dimensional space adaptively, for the user-friendly visualization of monitored network traffic. This work proposes two projection methods, namely, cooperative maximum likelihood Hebbian learning and auto-associative back-propagation networks, for the visual inspection of network traffic. This set of methods may be seen as a complementary tool in network security as it allows the visual inspection and comprehension of the traffic data internal structure. The proposed methods have been evaluated in two complementary and practical network-security scenarios: the on-line processing of network traffic at packet level, and the off-line processing of connection records, e.g. for post-mortem analysis or batch investigation. The empirical verification of the projection methods involved two experimental domains derived from the standard corpora for evaluation of computer network intrusion detection: the MIT Lincoln Laboratory DARPA dataset.     

Application of formal languages in polynomial transformations of instances between NP-complete problems

We propose the usage of formal languages for expressing instances of NP-complete problems for their application in polynomial transformations. The proposed approach, which consists of using formal language theory for polynomial transformations, is more robust, more practical, and faster to apply to real problems than the theory of polynomial transformations. In this paper we propose a methodology for transforming instances between NP-complete problems, which differs from Garey and Johnson’s. Unlike most transformations which are used for proving that a problem is NP-complete based on the NP-completeness of another problem, the proposed approach is intended for extrapolating some known characteristics, phenomena, or behaviors from a problem A to another problem B. This extrapolation could be useful for predicting the performance of an algorithm for solving B based on its known performance for problem A, or for taking an algorithm that solves A and adapting it to solve B.     

Whispering-gallery acoustic sensing: characterization of mesoscopic films and scanning probe microscopy applications

Full understanding of the physics underlying the striking changes in viscoelasticity, relaxation time, and phase transitions that mesoscopic fluid-like films undergo at solid-liquid interfaces, or under confinement between two sliding solid boundaries, constitutes one of the major challenges in condensed matter physics. Their role in the imaging process of solid substrates by scanning probe microscopy (SPM) is also currently controversial. Aiming at improving the reliability and versatility of instrumentation dedicated to characterize mesoscopic films, a noninvasive whispering-gallery acoustic sensing (WGAS) technique is introduced; its application as feedback control in SPM is also demonstrated. To illustrate its working principle and potential merits, WGAS has been integrated into a SPM that uses a sharp tip attached to an electrically driven 32-kHz piezoelectric tuning fork (TF), the latter also tighten to the operating microscope's frame. Such TF-based SPMs typically monitor the TF's state of motion by electrical means, hence subjected to the effects caused by the inherent capacitance of the device (i.e., electrical resonance differing from the probe's mechanical resonance). Instead, the novelty of WGAS resides in exploiting the already existent microscope's frame as an acoustic cavity (its few centimeter-sized perimeter closely matching the operating acoustic wavelength) where standing-waves (generated by the nanometer-sized oscillations of the TF's tines) are sensitively detected by an acoustic transducer (the latter judiciously placed around the microscope's frame perimeter for attaining maximum detection). This way, WGAS is able to remote monitoring, via acoustic means, the nanometer-sized amplitude motion of the TF's tines. (This remote-detection method resembles the ability to hear faint, but still clear, levels of sound at the galleries of a cathedral, despite the extraordinary distance location of the sound source.) In applications aiming at characterizing the dynamics of fluid-like mesoscopic films trapped under shear between the TF probe and the solid substrate, WGAS capitalizes on the well-known fact that the TF's motion is sensitively affected by the shear-forces (the substrate and its adsorbed mesocopic film playing a role) exert on its tip, which occurs when the latter is placed in close proximity to a solid substrate. Thus, WGAS uses a TF as an efficient transducer sandwiched between (i) the probe (that interact with the substrate and mesoscopic film), and (ii) the acoustic cavity (where an assessment of the probe mechanical motion is obtained). In short, WGAS has capability for monitoring probe-sample shear-force interactions via remote acoustic sensing means. In another application, WGAS can also be used as feedback control of the probe's vertical position in SPM. In effect, it is observed that when the microscope's probe stylus approaches a sample, a monotonic change of the WGAS acoustic signal occurs in the last ~20 nm before the probe touches the solid sample's surface, which allows implementing an automated-control of the probe-sample distance for safely scanning the tip across the sample surface. This principle is demonstrated by imaging the topographic features of a standard sample. Finally, it is worth to highlight that this alignment-free acoustic-based method offers a very direct assessment of the probe's mechanical motion state (the mechanical and the WGAS acoustic frequency responses coincide), which makes the WGAS a convenient metrology tool for studying surface interactions, including interfacial friction at the nanometer scale.     

An optimal fuzzy control system in a network environment based on simulated annealing. An application to a drilling process

This paper shows a strategy for the optimal tuning of a fuzzy controller in a networked control system using an offline simulated annealing approach. The optimal tuning of the fuzzy controller using a maximum known delay is based on the integral time absolute error (ITAE) performance index. The goal is to obtain the optimal tuning parameters for the input scaling factors where the ITAE performance index is minimized. In this study, a step change in the force reference signal is considered a disturbance, and the goal is to assess how well the system follows set-point changes using the ITAE criterion. In order to improve the efficiency of high-performance drilling processes while preserving tool life, the current study focuses on the design and implementation of an optimal fuzzy-control system for drilling force. Simulation results demonstrate good convergence properties of the proposed strategy. Experimental tests of the drilling of two materials (GGG40 and 17-4 PH) corroborate the excellent transient response and the minimum overshoot predicted by the simulation results. Thus, the optimal fuzzy control system reduces the influence of the increase in cutting force that occurs at larger drill depths, eliminating the risk of rapid drill wear and catastrophic drill breakage.     

A parallel strategy for biological sequence alignment in restricted memory space

Recently, many organisms had their DNA entirely sequenced, and this reality presents the need for aligning long DNA sequences, which is a challenging task due to its high demands for computational power and memory. The algorithm proposed by Smith–Waterman (SW) is an exact method that obtains optimal local alignments in quadratic space and time. For long sequences, quadratic complexity makes the use of this algorithm impractical. In this scenario, parallel computing is a very attractive alternative. In this paper, we propose and evaluate z-align, a parallel exact strategy based on the divergence concept to locally align long biological sequences using an affine gap function. Z-align runs in limited memory space, where the amount of memory used can be defined by the user. The results collected in a cluster with 16 processors presented very good speedups for long real DNA sequences. With z-align, we were able to compare up to 3 MBP (mega base-pairs) DNA sequences. As far as we know, this is the first time 3 MBP sequences are compared with an affine gap exact variation of the SW algorithm. Also, by comparing the results obtained with z-align and the popular BLAST tool, it is clear that z-align is able to produce longer and more significant alignments.     

M-CASH: A real-time resource reclaiming algorithm for multiprocessor platforms

Resource reclaiming schemes are typically applied in reservation-based real-time uniprocessor systems to support efficient reclaiming and sharing of computational resources left unused by early completing tasks, improving the response times of aperiodic and soft tasks in the presence of overruns. In this paper, we introduce a novel and efficient reclaiming algorithm, named M-CASH, for multiprocessor platforms. M-CASH leverages the resource reservation approach offered by the Multiprocessor CBS server offering significant improvements. The correctness of the algorithm is formally proven and its performance is evaluated through extensive synthetic simulations.

Segmentation and quantification of COVID-19 infections in CT using pulmonary vessels extraction and deep learning

Multimedia Tools and Applications - At the end of 2019, the World Health Organization (WHO) reported pneumonia that started in Wuhan, China, as a global emergency problem. Researchers quickly...     

Optimised photocatalytic degradation of a mixture of azo dyes using a TiO(2)/H(2)O(2)/UV process

The aim of the present study was to optimise the photocatalytic degradation of a mixture of six commercial azo dyes, by exposure to UV radiation in an aqueous solution containing TiO(2)-P25. Response surface methodology, based on a 3(2) full factorial experimental design with three replicates was employed for process optimisation with respect to two parameters: TiO(2) (0.1-0.9 g/L) and H(2)O(2) (1-100 mmol/L). The optimum conditions for photocatalytic degradation were achieved at concentrations of 0.5 g TiO(2)/L and 50 mmol H(2)O(2)/L, respectively. Dye mineralisation was confirmed by monitoring TOC, conductivity, sulfate and nitrate ions, with a sulfate ion yield of 96% under optimal reactor conditions. Complete decolorisation was attained after 240 min irradiation time for all tested azo-dyes, in a process which followed a pseudo-first kinetic order model, with a kinetic rate constant of approximately 0.018 min(-1). Based on these results, this photocatalytic process has promise as an alternative for the treatment of textile effluents.