Antibiotic and anesthetic drug release from double-setting α-TCP cements

The alpha phase of tricalcium phosphate (α-TCP) can form calcium-deficient hydroxyapatite (CDHA), similar to bone hydroxyapatite. α-TCP can be employed as a biocompatible cement and used as a drug vehicle. Double-setting α-TCP cement composed of acrylamide (α-TCP DS) has better mechanical properties than traditional α-TCP cement. However, no studies on the use of α-TCP DS-based systems for drug release have been reported. In this study, we prepared α-TCP- and α-TCP DS-based samples containing gentamicin sulfate, lidocaine hydrochloride, bupivacaine hydrochloride and levobupivacaine hydrochloride. The properties of the samples were characterized, and the use of the samples as vehicles for these drugs was evaluated. The cements were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, mechanical property tests and apparent porosity evaluation. The drug release in vitro was determined using ultraviolet–visible absorption spectroscopy. For statistical analysis, a confidence interval of 95% with a significance level < 5% was used. Neither the hydrogel nor the drugs interfered with the formation of CDHA, but they increased the mechanical strength of the studied cement. The Peppas–Sahlin model described the mechanisms involved in the drug-release kinetics process, revealing that Fickian diffusion was the main drug-release mechanism with a small influence from the Case II mechanism.     

Tidal current energy potential assessment in the Avilés Port using a three-dimensional CFD method

Clean Technologies and Environmental Policy - Tidal energy is considered as an energy resource of maximum interest in both technical and research fields due to its largely unexploited energy...     

Monte Carlo TD(λ)-methods for the optimal control of discrete-time Markovian jump linear systems

In this paper, we present an iterative technique based on Monte Carlo simulations for deriving the optimal control of the infinite horizon linear regulator problem of discrete-time Markovian jump linear systems for the case in which the transition probability matrix of the Markov chain is not known. We trace a parallel with the theory of TD(λ) algorithms for Markovian decision processes to develop a TD(λ) like algorithm for the optimal control associated to the maximal solution of a set of coupled algebraic Riccati equations (CARE). It is assumed that either there is a sample of past observations of the Markov chain that can be used for the iterative algorithm, or it can be generated through a computer program. Our proofs rely on the spectral radius of the closed loop operators associated to the mean square stability of the system being less than 1.     

SAR image processing using adaptive stack filter

Stack filters are a special case of non-linear filters. They have a good performance for filtering images with different types of noise while preserving edges and details. A stack filter decomposes an input image into several binary images according to a set of thresholds. Each binary image is filtered by a Boolean function. The Boolean function that characterizes an adaptive stack filter is optimal and is computed from a pair of images consisting of an ideal noiseless image and its noisy version. In this work the behavior of adaptive stack filters on synthetic aperture radar (SAR) data is evaluated. With this aim, the equivalent number of looks for stack filtered data are calculated to assess the speckle noise reduction capability of this filter. Then a classification of simulated and real SAR images is carried out on data filtered with a stack filter trained with selected samples. The results of a maximum likelihood classification of these data are evaluated and compared with the results of classifying images previously filtered using the Lee and the Frost filters.     

Discovering filter keywords for company name disambiguation in twitter

A major problem in monitoring the online reputation of companies, brands, and other entities is that entity names are often ambiguous (apple may refer to the company, the fruit, the singer, etc.). The problem is particularly hard in microblogging services such as Twitter, where texts are very short and there is little context to disambiguate. In this paper we address the filtering task of determining, out of a set of tweets that contain a company name, which ones do refer to the company. Our approach relies on the identification of filter keywords: those whose presence in a tweet reliably confirm (positive keywords) or discard (negative keywords) that the tweet refers to the company.We describe an algorithm to extract filter keywords that does not use any previously annotated data about the target company. The algorithm allows to classify 58% of the tweets with 75% accuracy; and those can be used to feed a machine learning algorithm to obtain a complete classification of all tweets with an overall accuracy of 73%. In comparison, a 10-fold validation of the same machine learning algorithm provides an accuracy of 85%, i.e., our unsupervised algorithm has a 14% loss with respect to its supervised counterpart.Our study also shows that (i) filter keywords for Twitter does not directly derive from the public information about the company in the Web: a manual selection of keywords from relevant web sources only covers 15% of the tweets with 86% accuracy; (ii) filter keywords can indeed be a productive way of classifying tweets: the five best possible keywords cover, in average, 28% of the tweets for a company in our test collection.     

Generating certified code from formal proofs: a case study in homological algebra

We apply current theorem proving technology to certified code in the domain of abstract algebra. More concretely, based on a formal proof of the Basic Perturbation Lemma (a central result in homological algebra) in the prover Isabelle/HOL, we apply various code generation techniques, which lead to certified implementations of the associated algorithm in ML. In the formal proof, algebraic structures occurring in the Basic Perturbation Lemma are represented in a way, which is not directly amenable to code generation with the available tools. Interestingly, this representation is required in the proof, while for the algorithm simpler data structures are sufficient. Our approach is to establish a link between the non-executable setting of the proof and the executable representation in the algorithm, which is to be generated. This correspondence is established within the logical framework of Isabelle/HOL—that is, it is formally proved correct. The generated code is applied to and illustrated with a number of examples.     

An unified approach for DTC design using interactive tools

This paper presents an interactive tool for dead-time compensator design. The tool is based on an unified dead-time compensator and considers models commonly used in industrial process control. The main contribution of this work is that the proposed tool and controller are simple to analyze and tune as they are based on an unique modified structure of the Smith predictor valid for every type of dead-time process (including integrating and unstable systems). Simple frequency analysis and block diagram transformations are used together with simulations to illustrate the main problems associated to the control of dead-time processes. Several examples of typical processes are presented to illustrate the fundamental concepts associated to the control of these systems. The interactive tool is not only useful for designing and analyzing but also for training and educational purposes.     

Cryptanalysis of the RNTS system

Internet of Things is a paradigm that enables communication between different devices connected to a local network or to Internet. Identification and communication between sensors used in Internet of Things and devices like smart-phones or tablets are established using radio frequency identification technology. However, this technology still has several security and privacy issues because of its severe computational constraints. In 2011, Jeong and Anh proposed the combined use of an authentication radio frequency identification protocol together with a ticket issuing system for bank services (in J. Supercomput. 55:307, 2011). In this paper we show that their message generation is weak, because it abuses the XOR operation and the use of a counter, which leaks too much secret protocol information. Our analysis shows important security faults that ruin most of the security properties claimed in the original paper. More precisely, information privacy (via a disclosure and leakage attack) and location privacy (traceability attack) are both compromised. Moreover, an attacker can disrupt the proper working of the system by exploiting the fact that message integrity is not properly checked.     

Rethinking universal accessibility: a broader approach considering the digital gap

The universal accessibility concept is usually formulated in terms that ignore the socioeconomic and sociopolitical contexts. Therefore, it has impact only on a small fraction of the global population of people with disabilities. This issue raises the need for a comprehensive approach that takes into account issues related to literacy, availability of technology, digital literacy, the use of minority languages, etc.