State space reduction by non-standard semantics for deadlock analysis

In recent years many techniques have been developed for automatically verifying concurrent systems and most of them are based on the representation of the concurrent system by means of a transition system. State explosion is one of the most serious problems of this approach: often the prohibitive number of states renders the verification inefficient and, in some cases, impossible.

We propose a method for reducing the state space of the transition system corresponding to a CCS process that suites deadlock analysis. The reduced transition system is generated by means of a non-standard operational semantics containing a set of rules which are, in some sense, an abstraction, preserving deadlock freeness, of the inference rules of the standard semantics. Our method does not build the standard transition system, but directly generates an abstract system with a fewer number of states, so saving memory space. We characterize a class of processes whose abstract transition system is not exponential in the number of parallel components.     

Nicola Zabaglia and the School of Practical Mechanics of the Fabbrica of St. Peter’s in Rome

Nicola Zabaglia, master mason of the Fabbrica of St. Peter’s and inventor of many ingenious mechanical devices for restoration, was also the director of the “School of Practical Mechanics” for the education of young labourers. At a time when traditional operational experience was strongly rivalled by the coeval achievements in the theory of mechanics and its effect on building, the work of Zabaglia became an instrument of propaganda. Since empirical practice and the oral transmission of operational knowledge were called into question by the pressing progress of science as well as by new institutions, the works of Zabaglia and his talented students were not only an influential model of cohesion between architecture, building yard and applied mechanics, but also a melancholy epilogue of a practical tradition inexorably condemned to oblivion.     

Syntactic reductions for efficient deadlock analysis

A well‐known problem in the verification of concurrent systems based on model checking is state explosion: concurrent systems are often represented by automata with a prohibitive number of states. A reduction technique to reduce state explosion in deadlock checking is presented. The method is based on an automatic syntactic simplification of a calculus of communicating systems (CCS) specification, which keeps the parts of the program structure that may lead to a deadlock and deletes the other parts. Copyright © 2002 John Wiley & Sons, Ltd.     

Influence of regioirregular structural units on the crystallization of isotactic polypropylene

Seven samples of isotactic polypropylene were examined to study the influence on the formation of the γ crystalline phase of possible regiodefects along the chain. Wide‐angle X‐ray diffraction allowed the determination of the percentage of the γ phase in the samples and ¹³C‐NMR spectroscopy was used to correlate the development of the γ phase with the existence of regioirregular structural units along the chain. Furthermore, it was possible to appraise the contributions given by the different families of lamellae to the small‐angle X‐ray diffraction patterns. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 375–384, 2001     

Sequential Motion of 4D Printed Photopolymers with Broad Glass Transition

The term “4D printing” refers to the development of stimulus‐responsive structures through 3D printing of active smart materials, typically shape memory polymers. A noteworthy aim of this research field is to obtain objects able to display complex shape‐shifting motions, such as sequential transformations over time. In this work, this peculiar response is studied on a commercial photopolymer, printed by stereolithography and featuring, on the basis of its inherent broad glass transition, the so‐called “temperature‐memory effect” (TME). The TME, that is, a response in which the shape memory effect occurs on a region controlled by the deformation temperature, is studied in shape memory cycles where the deformation temperature is systematically varied, so to provide a correlation between deformation and recovery temperatures. This also allows to properly select two temperatures at which deforming a specimen along a multistep history, so as to finally separate each recovery process on the temperature and time scales. This sequential recovery is studied in double folded bars, with arms deformed at different temperatures, and on a properly designed self‐locking clamp. The obtained results are promising for the realization of smart temperature‐responsive structures printed with one single polymer and capable of multiple shape transformations.     

Effect of electrospun fibers of polyhydroxybutyrate filled with different organoclays on morphology,biodegradation, and thermal stability of poly(ε‐caprolattone)

The properties of nanocomposites of poly(ε‐caprolattone) (PCL) were studied, the pristine PCL was implemented with the introduction of electrospun fibers of polyhydroxybutyrate (PHB), containing a cationic (Cloisite) or an anionic (Perkalite) clay. These multicomponent composites containing a very low amount of clay confined in fibers are different from usual nanocomposite materials containing clay dispersed in the polymer matrix, which are produced by solvent casting or melt extrusion. To analyze the influence of the different fillers on the final composite, a preliminary study on PHB cast films and fibers prepared from the same solution was carried out, and then a thorough analysis was accomplished of the behavior of these particular nanocomposites PCL/PHB fibers/clay to elucidate the effects of the filled electrospun fibers on the PCL matrix. The structure and morphology of the samples were characterized by wide‐angle X‐ray diffraction and small angle X‐ray scattering; differential scanning calorimetry and thermogravimetric analysis were used to understand the influence of the fillers on the thermal behavior and stability; mechanical properties were evaluated and biodegradation studies were carried out. The PHB electrospun fibers and the fractured surface of the final composites were examined by scanning electron microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42342.     

Hot topic: Bisphenol A in cow milk and dietary exposure at the farm level

Chemical hazards may enter the milk chain during primary production. The study, for the first time, investigated the occurrence of bisphenol A (BPA) levels in cow milk samples collected on the farm following manual or mechanical milking and from the cooling tank. We applied a new monitoring model based on the identification of the hazards at each stage of the milk chain to identify potential pathways for contamination along the milk chain. We evaluated exposure to BPA through milk consumption based on detected contamination levels and the temporary tolerable daily intake established by the European Food Safety Authority (EFSA). Milk samples (n = 72) were analyzed using liquid chromatography with fluorescence detection. The mean BPA concentrations were 0.757 µg/L in manually milked samples, 0.580 µg/L in mechanically milked samples, and 0.797 µg/L in milk from the cooling tank. Bisphenol A occurred in the milk chain as a result of different stages of milking, and reached the highest levels at the end of the milk chain. Although the dietary intake of BPA was below the EFSA's temporary tolerable daily intake, exposure to BPA, even at low doses, through milk consumption represents a public health concern. Therefore, to ensure milk safety, new monitoring plans should be applied based on the identification of hazards at each stage of the milk chain.     

Chromatic weathering of black limestone quarried in Varenna (Lake Como,Italy)

The causes of chromatic weathering in black limestone have been investigated on samples from the main quarry of Varenna (Lake Como, Italy), which provided building stones for Lombard architecture. Our studies have been carried out combing colorimetric, mineralogical, chemical, microstructural and geochemical observations. The results suggest that the chromatic weathering affecting the surfaces of black limestone is not due to oxidation of the original organic matter present in the bulk, as believed. Chemical and mechanical weathering associated with the deposition of new organic matter are the most important phenomena occurring on the surface, leading to a diffuse roughness of surface and de-cohesion.     

Hair analysis for abused drugs by capillary zone electrophoresis with field-amplified sample stacking

The present paper describes the methodological optimisation and validation of a capillary zone electrophoresis method for the determination of morphine, cocaine and 3,4-methylenedioxymethamphetamine (MDMA) in hair, with injection based on field-amplified sample stacking. Diode array UV absorption detection was used to improve analytical selectivity and identification power. Analytical conditions: running buffer 100 mM potassium phosphate adjusted to pH 2.5 with phosphoric acid, applied potential 10 kV, temperature 20 degrees C, injection by electromigration at 10 kV for 10 s, detection by UV absorption at the fixed wavelength of 200 nm or by recording the full spectrum between 190 and 400 nm. Injection conditions: the dried hair extracts were reconstituted with a low-conductivity solvent (0.1 mM formic acid), the injection end of the capillary was dipped in water for 5 s without applying pressure (external rinse step), then a plug of 0.1 mM phosphoric acid was loaded by applying 0.5 psi for 10 s and, finally, the sample was injected electrokinetically at 10 kV for 10 s. Under the described conditions, the limit of detection was 2 ng/ml for MDMA, 8 ng/ml for cocaine and 6 ng/ml for morphine (with a signal-to-noise ratio of 5). The lowest concentration suitable for recording interpretable spectra was about 10-20-times the limit of detection of each analyte. The intraday and day-to-day reproducibility of migration times (n = 6), with internal standardisation, was characterised by R.S.D. values < or = 0.6%; peak area R.S.D.s were better than 10% in intraday and than 15% in day-to-day experiments. Analytical linearity was good with R2 better than 0.9990 for all the analytes.     

Concurrent behavior: A construct to specify the external behavior of objects in object databases

We present a linguistic construct to define concurrency control for the objects of an object database. This construct, calledconcurrent behavior, allows to define a concurrency control specification for each object type in the database; in a sense, it can be seen as a type extension. The concurrent behavior is composed by two parts: the first one, calledcommutativity specification, is a set of conditional rules, by which the programmer specifies when two methods do not conflict each other. The second part, the constraint specification, is a set of guarded regular expressions, calledconstraints, by which the programmer defines the allowed sequences of method calls. At each time during an actual execution, a subset of constraints may be active so limiting the external behavior of the object. A constraint becomesactive when its guard is verified, where a guard is composed of the occurrence of some method callm along with the verification of a boolean expression on the object state and the actual parameters ofm. A constraint dies when a string of the language corresponding to the regular expression has been recognized. While the commutativity specification is devoted to specify the way in which the external behavior of an object is influenced by the existence of concurrent transactions in the system, the constraint specification defines the behavior of the object, independently from the transactions. Since the two parts of the concurrent behavior are syntactically distinct and, moreover, each of them consists of a set of independent rules, modularity in specifying the objects is enhanced, with respect to a unique specification. We outline an implementation of the construct, which is based on a look-ahead policy: at each method execution, we foresee the admissible successive behaviors of the object, instead of checking the admission of each request at the time it is actually made.