A formally verified hybrid system for safe advisories in the next-generation airborne collision avoidance system

The Next-Generation Airborne Collision Avoidance System (ACAS X) is intended to be installed on all large aircraft to give advice to pilots and prevent mid-air collisions with other aircraft. It is currently being developed by the Federal Aviation Administration (FAA). In this paper, we determine the geometric configurations under which the advice given by ACAS X is safe under a precise set of assumptions and formally verify these configurations using hybrid systems theorem proving techniques. We consider subsequent advisories and show how to adapt our formal verification to take them into account. We examine the current version of the real ACAS X system and discuss some cases where our safety theorem conflicts with the actual advisory given by that version, demonstrating how formal hybrid systems proving approaches are helping to ensure the safety of ACAS X. Our approach is general and could also be used to identify unsafe advice issued by other collision avoidance systems or confirm their safety.     

Antioxidant properties of industrial heat-treated milk

Milk is a source of antioxidant compounds in a delicate balance between anti- and pro-oxidative processes. This research aims at evaluating the antioxidant properties of industrial heat treated milk (UHT, Microfiltered and High Quality Pasteurized) with particular attention towards the characterization of unsaponifiable fraction, rich in antioxidant compounds, and its contribution to radical scavenging activity. Total polyphenol content, FRAP, DPPH and colour, often related to antioxidant properties, were performed on milk. Moreover, the unsaponifiable fraction of milk samples was studied for: (a) α-tocopherol, β-carotene, retinol isomers, cholesterol and two previously developed indices Degree of Retinol Isomerization (DRI) and Degree of Antioxidant Protection (DAP); (b) DPPH assay; (c) a qualitative analysis of its major functional groups by Fourier Transformed infrared spectroscopy (FTIR) on Attenuated Total Reflectance (ATR). UHT milk showed the highest values in all assays, probably due to the development of antioxidant compounds, that occur during this severe heat-treatment and confirmed by a moderate correlation (r?=?0.6791) between DPPH and b*(yellowness). On unsaponifiable fraction, differences were detected on 13-cis retinol and confirmed by DRI index and specific vibrations of functional groups of antioxidants were identified in FTIR-ATR spectra.     

Unusual Lipid A from a Cold‐Adapted Bacterium: Detailed Structural Characterization

Colwellia psychrerythraea 34H is a Gram‐negative cold‐adapted microorganism that adopts many strategies to cope with the limitations associated with the low temperatures of its habitat. In this study, we report the complete characterization of the lipid A moiety from the lipopolysaccharide of Colwellia. Lipid A and its partially deacylated derivative were completely characterized by high‐resolution mass spectrometry, NMR spectroscopy, and chemical analysis. An unusual structure with a 3‐hydroxy unsaturated tetradecenoic acid as a component of the primary acylation pattern was identified. In addition, the presence of a partially acylated phosphoglycerol moiety on the secondary acylation site at the 3‐position of the reducing 2‐amino‐2‐deoxyglucopyranose unit caused tremendous natural heterogeneity in the structure of lipid A. Biological‐activity assays indicated that C. psychrerythraea 34H lipid A did not show an agonistic or antagonistic effect upon testing in human macrophages.     

On-line 2-satisfiability

We deal with the followingon-line 2-satisfiability problemP(m, n): starting fromC(0)=true, consider a sequence ofm Boolean formulasC(k) (inn variables and in conjunctive normal form), each of them being the intersection of the previous one with a single clause which is the union of two literals. Solve the sequence of 2-satisfiability problemsC(k)=true,k=1,...,m. It is well known that a 2-satisfiability problem involvingm clauses can be solved inO(m) time. Thus, by a naive approach one can solveP(m, n) in overallO(m ²) time. We present an algorithm with overallO(nm) time complexity, which for every formula not only checks its satisfiability, but also actually computes a solution (if any), and moreover, detects all forced and all identical variables. Our algorithm makes use of an efficient on-line transitive closure procedure by Italiano. We discuss two applications to the design of integrated electronic circuits and to edge classification in automated perception.To the memory of Bob Jeroslow     

A study of the suitability of the KENTORT II eastern shale oil for asphalt paving applications

The uncertain future of petroleum reserves has fuelled the search for alternative resources. A feasibility study was conducted to determine potential paving applications of the oil extracted from eastern shale by the KENTORT II process. The eastern shale oil (ESO) in this study was separated into two drastically different viscosity portions, designated as ‘hard’ and ‘soft’ ESO. It was hypothesized that the ‘hard’ portion might enhance the asphalt performance by increasing the stiffness. It was discovered that the ‘hard’ ESO modified asphalt properties deteriorate significantly with time. On the other hand, the ‘soft’ ESO was found to exhibit desirable properties in an asphalt recycling application. Further studies are recommended to fully characterize the binder and mixture properties of ESO modified/rejuvenated asphalts.     

Normalized Cut optimization based on color perception findings. A comparative study

This paper proposes a methodology to obtain a fully automatic color segmentation algorithm based on the Normalized Cut (Ncut) proposed by Shi and Malik, using recent findings in color perception. A weighting matrix computed using a perceptually uniform color space (CIE \(L^*a^*b^*\) ) and color distance formulae correlated with the visually perceived color differences (CIE94 and CIEDE2000); a stopping condition related to perceptual criteria; an automatic parameters setting required to compute the affinity matrix are proposed. To test the proposed methodology, a wide study about the influence of the color space choice, different stopping conditions, and different similarity measurements is carried out. These alternatives are exhaustively evaluated using perception-related measurements (S-CIELAB) and general segmentation evaluation metrics applied to the 500 images of the Berkeley database. The results showed that the proposed method outperforms Ncut based on other color spaces, similarity measure or stopping conditions. Furthermore, the usability of the method is increased by replacing the manual parameter setting for an automatic.     

X-ray microscopy of plant cells by using LiF crystal as a detector

A lithium fluoride (LiF) crystal has been utilized as a new soft X-ray detector to image different biological samples at a high spatial resolution. This new type of image detector for X-ray microscopy has many interesting properties: high resolution (nanometer scale), permanent storage of images, the ability to clear the image and reuse the LiF crystal, and high contrast with greater dynamic range. Cells of the unicellular green algae Chlamydomonas dysosmos and Chlorella sorokiniana, and pollen grains of Olea europea have been used as biological materials for imaging. The biological samples were imaged on LiF crystals by using the soft X-ray contact microscopy and contact micro-radiography techniques. The laser plasma soft X-ray source was generated using a Nd:YAG/Glass laser focused on a solid target. The X-ray energy range for image acquisition was in the water-window spectral range for single shot contact microscopy of very thin biological samples (single cells) and around 1 keV for multishots microradiography. The main aim of this article is to highlight the possibility of using a LiF crystal as a detector for the biological imaging using soft X-ray radiation and to demonstrate its ability to visualize the microstructure within living cells.     

High-resolution water window X-ray imaging of in vivo cells and their products using LiF crystal detectors

High contrast imaging of in vivo Chlorella sorokiniana cells with submicron spatial resolution was obtained with a contact water window X-ray microscopy technique using a point-like, laser-plasma produced, water-window X-ray radiation source, and LiF crystals as detectors. This novel type of X-ray imaging detectors is based on photoluminescence of stable electronic point defects, characterized by high intrinsic resolution. The fluorescence images obtained on LiF crystals exposed in single-shot experiments demonstrate the high sensitivity and dynamic range of this new detector. The powerful performances of LiF crystals allowed us to detect the exudates of Chlorella cells in their living medium and their spatial distribution in situ, without any special sample preparation.     

An Empirical Investigation Into Typing Errors in Interactive Digital Television Applications

Remote controls are especially problematic for writing text, something necessary in many interactive digital TV applications (IDTV). In the context of research aimed at finding effective entry methods for IDTV applications, an empirical investigation was carried out and is presented in this article. The study analyzed the errors committed by 82 users in an experiment in which they wrote 7,395 sentences. Several typing methods suitable for IDTV contexts were used for experimentation. There were 3,562 of the sentences that registered at least one error. These errors were classified and their main causes analyzed, the particular characteristics of the users taken into account. The results show that the most frequent errors are proximity mistakes in all the evaluated methods. They appear in between 13.75% and 32.31% of the sentences, depending on the input method. Also, age and background are major aspects affecting the number and type of mistakes. The results could be the basis of changes in the design of conventional remote controls or in the design of advanced techniques for error recognition and correction.