Polymerization by crystallization of trioxane from cyclohexane solutions in presence of 1,3-dioxolane

Trioxane–1,3-dioxolane copolymers of high molecular weights and good thermal stability are obtained with high yields by a crystallization-polymerization method. The feed consists of concentrated solutions of trioxane in cyclohexane in the presence of dissolved 1,3-dioxolane. The 1,3-dioxolane/trioxane molar ratio in the feed lies in the range 2 to 10%. The results are compared with those obtained from isothermal copolymerizations.     

A numerical method for solving equilibrium problems of masonry-like solids

This paper proposes a numerical method for the solution of equilibrium problems of solids which do not support tension. Some boundary-value problems are solved numerically and the solution obtained is compared to the exact one.

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Sommario In questo lavoro viene proposto un metodo numerico per la soluzione di problemi di equilibrio di solidi non resistenti a trazione. Vengono successivamente risolti numericamente alcuni problemi di equilibrio e la soluzione ottenuta è confrontata con quella esatta.

     

Elastic-plastic behaviour with work-hardening: An appropriate model for structural software

Summary A method is proposed for the stress analysis of structures subject to elastic and plastic deformations. The method can be adapted to exploit existing computing programs for elastic stress analysis and is sufficiently subtle to describe a variety of types of work-hardening, on the basis of a limited number of essential material parameters which can be read off usually available test graphs.

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Sommario Si propone un metodo per l'analisi di strutture soggette a deformazioni elasto-plastiche. Il metodo può essere adattato in modo da sfruttare programmi di calcolo, di cui già si disponga, per l'analisi elastica di strutture ed è sufficientemente duttile da consentire la rappresentazione di tipi diversi di incrudimento, con l'uso di un numero limitato di parametri materiali che possono dedursi da grafici sforzo-deformazione generalmente disponibili.

     

The Anti-Inflammatory Effect of a γ-Lactone Isolated from Ostrich Oil of Struthio camelus (Ratite) and Its Formulated Nano-Emulsion in Formalin-Induced Paw Edema

The ostrich oil of Struthio camelus (Ratite) found uses in folk medicine as an anti-inflammatory in eczema and contact dermatitis. The anti-inflammatory effect of a γ-lactone (5-hexyl-3H-furan-2-one) isolated from ostrich oil and its formulated nano-emulsion in formalin-induced paw edema was investigated in this study. Ostrich oil was saponified using a standard procedure; the aqueous residue was fractionated, purified, and characterized as γ-lactone (5-hexyl-3H-furan-2-one) through the interpretation of IR, NMR, and MS analyses. The γ-lactone was formulated as nano-emulsion using methylcellulose (MC) for oral solubilized form. The γ-lactone methylcellulose nanoparticles (γ-lactone-MC-NPs) were characterized for their size, shape, and encapsulation efficiency with a uniform size of 300 nm and 59.9% drug content. The γ-lactone was applied topically, while the formulated nanoparticles (NPs) were administered orally to rats. A non-steroidal anti-inflammatory drug (diclofenac gel) was used as a reference drug for topical use and ibuprofen suspension for oral administration. Edema was measured using the plethysmograph method. Both γ-lactone and γ-lactone-MC-NPs showed reduction of formalin-induced paw edema in rats and proved to be better than the reference drugs; diclofenac gel and ibuprofen emulsion. Histological examination of the skin tissue revealed increased skin thickness with subepidermal edema and mixed inflammatory cellular infiltration, which were significantly reduced by the γ-lactone compared to the positive control (p-value = 0.00013). Diuretic and toxicity studies of oral γ-lactone-MC-NPs were performed. No diuretic activity was observed. However, lethargy, drowsiness, and refusal to feeding observed may limit its oral administration.     

Matching signatures and Pfaffian graphs

Perfect matchings of k-Pfaffian graphs may be enumerated in polynomial time on the number of vertices, for fixed k. In general, this enumeration problem is #P-complete. We give a Composition Theorem of 2r-Pfaffian graphs from r Pfaffian spanning subgraphs. Constructions of k-Pfaffian graphs known prior to this seem to be of a very different and essentially topological nature. We apply our Composition Theorem to produce a bipartite graph on 10 vertices that is 6-Pfaffian but not 4-Pfaffian. This is a counter-example to a conjecture of Norine (2009) [8], which states that the Pfaffian number of a graph is a power of four.     

Equilibrium Problems and Limit Analysis of Masonry Beams

We consider planar straight and curved masonry beams with the constitutive equation from Orlandi (Ph.D. thesis, 1999) and Zani (Eur. J. Mech. A, Solids 23:467–484, 2004). After stating some results about the solution to the boundary value problem, the limit analysis for this kind of bodies is outlined, based on energetic considerations (Lucchesi et al. in Q. Appl. Math. 68:713–746, 2010). The static and kinematic theorems of limit analysis, which usually are justified in a heuristic way (Heyman in The Masonry Arch, 1982; Kooharian in Proc. - Am. Concr. Inst. 89:317–328, 1953), are examined from this point of view. It is seen that the kinematic theorem does not always hold but can be proved under some hypotheses that are frequently met in applications.     

Accurate measurement in the field of the earth of the general-relativistic precession of the LAGEOS II pericenter and new constraints on non-newtonian gravity

The pericenter shift of a binary system represents a suitable observable to test for possible deviations from the newtonian inverse-square law in favor of new weak interactions between macroscopic objects. We analyzed 13 years of tracking data of the LAGEOS satellites with GEODYN II software but with no models for general relativity. From the fit of LAGEOS II pericenter residuals we have been able to obtain a 99.8% agreement with the predictions of Einstein's theory. This result may be considered as a 99.8% measurement in the field of the Earth of the combination of the γ and β parameters of general relativity, and it may be used to constrain possible deviations from the inverse-square law in favor of new weak interactions parametrized by a Yukawa-like potential with strength α and range λ. We obtained |α| ? 1 × 10(-11), a huge improvement at a range of about 1 Earth radius.     

Bounded shear stress in masonry-like bodies

In the paper, a hyperelastic material with limited tensile and compressive strength is considered. In addition, the maximum value of the tangential component of the stress that can be attained on each plane depends on the intensity of the normal component. Previously formulated for the plane case, the constitutive equation of this material is now extended to three-dimensional bodies, constituting henceforth a generalization of the well-known model of masonry-like materials. The proposed constitutive law has been implemented in the finite element code MADY and has been applied to the study of masonry panels under different load conditions.