Semantic foundations for generalized rewrite theories

Rewriting logic (RL) is a logic of actions whose models are concurrent systems. Rewrite theories involve the specification of equational theories of data and state structures together with a set of rewrite rules that model the dynamics of concurrent systems. Since its introduction, more than one decade ago, RL has attracted the interest of both theorists and practitioners, who have contributed in showing its generality as a semantic and logical framework and also as a programming paradigm. The experimentation conducted in these years has suggested that some significant extensions to the original definition of the logic would be very useful in practice. These extensions may develop along several dimensions, like the choice of the underlying equational logic, the kind of side conditions allowed in rewrite rules and operational concerns for the execution of certain rewrites. In particular, the Maude system now supports subsorting and conditional sentences in the equational logic for data, and also frozen arguments to block undesired nested rewrites; moreover, it allows equality and membership assertions in rule conditions. In this paper, we give a detailed presentation of the inference rules, model theory, and completeness of such generalized rewrite theories. Our results provide a mathematical semantics for Maude, and a foundation for formal reasoning about Maude specifications.     

A simple GC–MS method for the screening of betulinic,corosolic, maslinic,oleanolic and ursolic acid contents in commercial botanicals used as food supplement ingredients

The occurrence of triterpene pentacyclic acids in plants is extensive, but little is known about their availability in commercial extracts. A simple GC–MS method for the simultaneous determination of betulinic, corosolic, maslinic, oleanolic and ursolic acids was developed and applied to 38 different commercial plant extracts sold as ingredients for dietary supplements. A suitable protocol was set up to perform routine control of a diverse array of samples with different botanical, chemical and physical characteristics. Remarkable quantities of corosolic acid were found in dried extracts from aerial parts of Lagerstroemia speciosa and Ortosiphon stamineus (14233 and 1132 mg/kg, respectively), while oleanolic acid was abundant in O. stamineus and Crataegus monogyna flowers (2774 and 2339 mg/kg); ursolic was identified in O. stamineus, C. monogyna, L. speciosa and Arctostaphylos uva-ursi leaves (7773, 4165, 2108 and 1034 mg/kg). Only L. speciosa was rich in maslinic acid (4958 mg/kg), while minor amounts of betulinic acid (257 and 80 mg/kg) were detected in L. speciosa and C. monogyna extracts. Lower quantities of triterpenic acids were identified in dried extracts of Harpagophyton procumbens root, propolis, Punica granatum root, Styrax benzoin, Vaccinium myrtillus fruits and Vitis vinifera seeds. Decoctions and fluid extracts lacked or contained very low amounts of triterpenic acids. Results are discussed in terms of quality and safety of these ingredients.     

Identification of natural dyes on laboratory-dyed wool and ancient wool, silk, and cotton fibers using attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy and Fourier transform Raman spectroscopy

Attenuated total reflection (ATR) infrared and Fourier transform (FT) Raman spectra were obtained from wool threads dyed in the laboratory with natural dyes used in antiquity, following a procedure similar to ancient methods for dyeing wool. The ATR spectra were primarily dominated by the signals of the wool, making it difficult to identify the dye on the fibers only by visual inspection of the infrared spectrum. However, the Raman spectra showed more significant characteristics attributable to the dyes as previously studied in the literature on modern synthetic dyes. A library-search method was thus applied to the second derivatives of both the ATR and Raman spectra to verify the possibility of identifying the dye. Two libraries were constructed, one consisting of the ATR spectra of undyed wool (raw, washed, and mordanted) and the transmission spectra of pure dyes and the other consisting of the Raman spectra of undyed wool and of pure dyes. Correlation and first-derivative correlation search algorithms were used. The results presented here suggest that the two types of spectroscopy are complementary in this kind of work, allowing the almost complete identification of historic dyes on wool. In fact, through the combined use of the two searches, most dyes were identified with a good index of similarity and within the first five hits. Only for annatto was identification totally impossible using either technique. Subsequently the same method was applied to wool, silk, and cotton threads taken from ancient Caucasian and Chinese textiles.     

Post-welding formability of AZ31 magnesium alloy

The plastic flow behaviour and formability of friction stir welded AZ31 magnesium alloys were widely investigated. Flow curves were obtained in extended ranges of temperature (250–350 °C) and strain rate (0.001–0.1 s⁻¹) by means of uniaxial tensile tests; furthermore, forming limit curves were determined using the hemispherical punch method in the same range of temperature but with a constant crosshead speed of 0.1 mm/s. The results were compared with those obtained, under the same experimental conditions, on the base material. The flow stress levels of joint and base material are very similar up the peak of the flow curve although the equivalent strains at the peak and to failure are usually lower than those of base material. However, at the highest temperature and lowest strain rate investigated (350 °C and 0.001 s⁻¹), the flow behaviour of the welded joint tends to be similar to the one of the base alloy. Finally, formability of the friction stir welded material, evaluated in terms of forming limit curves, is usually lower than the one of the base material.     

Selective effect of cholesterylphosphoserine on intracellular cholesterol transport

Cholesteryl-3β-phosphoserine (CPHS) is a synthetic steroid affecting intracellular cholesterol transport. To compare CPHS with the well-known inhibitors progesterone and U18666A, we examined cholesterol transport in three human cell lines: the monocytic U-937, the endothelial ECV-304, and the lymphoid Jurkat. Under low density lipoprotein (LDL) loading, CPHS inhibited cholesterol esterification in U-937 and ECV-304 cells but not in Jurkat cells. In contrast, CPHS inhibited the mobilization of plasma membrane cholesterol induced by 25-hydroxycholesterol, brefeldin A, or sphingomyelinase in all cell lines. In cells pulse-labeled with [³H] cholesterol, CPHS decreased incorporation of cholesterol and inhibited its esterification. In prelabeled cells, CPHS promoted cholesterol efflux and enhanced the cyclodextrin-mediated removal of plasma membrane cholesterol. CPHS did not affect endogenous cholesterol synthesis nor acylcoenzyme A: cholesterol acyltransferase activity. These data suggest that, unlike progesterone and U18666A, CPHS inhibits intracellular cholesterol transport by specifically affecting the movements of cholesterol in the plasma membrane. Owing to this restricted site of action, CPHS may help to clarify the role of the plasma membrane in cholesterol trafficking. For example, the lack of an effect of CPHS on the esterification of LDL-derived cholesterol in Jurkat cells suggests that most of the LDL-derived cholesterol in these cells is directly delivered to the endoplasmic reticulum without cycling through the plasma membrane.     

Sphingomyelinase increases 2-deoxyglucose uptake and glucose metabolism of human platelets

Recent studies have shown that the sphingomyelinase (SMase) catalyzed hydrolysis of sphingomyelin (SM) represents an important cell signalling pathway. Control of SMase activity appears to be crucial for the regulation of multiple biological events in different cell systems; in particular, SMase activity appears to be involved in the control of vascular functions and in atherogenic events. Here we report that SMase treatment of human platelets significantly increases 2-deoxyglucose uptake by decreasing K(m) value of sugar transport and increasing sugar diffusion. In addition SMase treatment enhances basal glycolytic flux of platelets as well as the stimulation of the flux induced by suboptimal concentration of thrombin. The present study demonstrates that exposure of platelets to SMase, which may take place in vivo in physiological and/or in pathological conditions, modifies biochemical parameters of resting and stimulated platelets which are essential for cell physiological role.     

Effect of temperature,strain rate and fibre orientation on the plastic flow behaviour and formability of AZ31 magnesium alloy

The sheet formability of AZ31 magnesium alloy has been widely investigated by means of uniaxial tensile and hemispherical punch tests, performed at different temperatures and strain rates, using samples with different fibre orientations. The results of the uniaxial tensile tests were analysed in terms of flow curves, ductility and microstructural evolution. They show that the flow stress decreases and ductility increases as temperature rises and strain rate reduces; the ductility is almost independent of the fibre orientation that, however, slightly affects the flow stress values. The formability, described by the forming limit curves (FLCs), improves with increasing temperature and decreasing strain rate. Moreover, formability along the rolling direction (RD) is higher than that along the transversal one (TD), even if the FLCs obtained along the TD have a larger extension in the drawing side than the ones along the RD. Such behaviours were related to the constitutive parameters and microstructure developed during deformation.     

Modelling Dynamic Software Architectures using Typed Graph Grammars

Several recent research efforts have focused on the dynamic aspects of software architectures providing suitable models and techniques for handling the run-time modification of the structure of a system. A large number of heterogeneous proposals for addressing dynamic architectures at many different levels of abstraction have been provided, such as programmable, ad-hoc, self-healing and self-repairing among others. It is then important to have a clear picture of the relations among these proposals by formulating them into a uniform framework and contrasting the different verification aspects that can be reasonably addressed by each proposal. Our work is a contribution in this line. In particular, we map several notions of dynamicity into the same formal framework in order to distill the similarities and differences among them. As a result we explain different styles of architectural dynamisms in term of graph grammars and get some better insights on the kinds of formal properties that can be naturally associated to such different specification styles. We take a simple automotive scenario as a running example to illustrate main ideas.     

Effect of high alumina cement on permeability and structure properties of ZrO2 composites

Porous ZrO₂ based ceramics are widely used for filtration/separation processes due to the good chemical and thermal stability. For these applications it is desirable that the material have a controlled porous structure in order to obtain good permeability. In this study Ca stabilized ZrO₂ composites were developed from a starting mixture of pure ZrO₂ containing different mole proportions of calcium aluminate cement. Ceramics disks were uniaxially pressed and subsequently sintered at 1300–1450 °C. The influence of process parameters such as chemical compositions and sintering temperature on textural characteristics (volume fraction of pores, pore size distribution) and permeability was followed by apparent density measurements, Hg porosimetry and N₂ permeation, respectively. Sintered microstructure was examined by scanning electron microscopy SEM. The XRD analysis showed that m-ZrO₂ transformed to tetragonal and/or cubic ZrO₂, these phases probably coexisted at relatively low CaO addition. For 30 mol% addition, amount of the cubic Ca_0.15Zr_0.85O_1.85 phase appreciably increased. At 50 mol% CaO, CA₂ was the major phase of the composite with minor CaZrO₃ formation whereas relative content c-ZrO₂ is slightly reduced.The composites had 30–40 vol% porosity with typical pore radius of 1–1.3 μm and the corresponding Darcian permeability k₁ values varied between 2 and 4 × 10^?14 m², such structure parameters slightly increased for high cement addition. The k₁ of ceramics produced from 50 mol% CaO composition remained nearly constant up to 1450 °C due to similar densification degree. The experimental permeability dependence on pore structure parameters as well as the comparison with the value estimated by Ergun's equation are showed.