Geometry,mechanical properties and mounting of perforated plates for ballistic application

In this paper, the ballistic resistance of perforated plates made of different types of steel, mounting and geometry was investigated. Different types of steel in various heat treatment conditions were tested. Target mounting was also varied: rigid, oblique and hanging. Furthermore, four different perforated plate geometries were tested: two plate thicknesses and two hole diameters. Their behaviour was tested using impact from firing 12.7 mm M-8 API ammunition at eleven perforated plate samples. These samples were placed by means of a steel frame over a 13 mm RHA plate, at two distances. Damaged area on targets was correlated to ballistic resistance of the whole armour to find the optimal perforated plate. It was found that perforated plates, in optimized case offer a frequent fracture of the penetrating core in up to five parts. This debris is unable to penetrate the basic plate, offering mass effectiveness of the whole armour model of 1.76 and the mass effectiveness of the perforated plate of 5.91.     

Identification of acid attack on concrete of a sewage system

A sewage system, 300 km long, showed superficial deterioration of concrete just 2 years after construction. In order to re-habilitate the structure, it was necessary to identify the main mechanism of deterioration and to understand the heterogeneous distribution of the damage observed. The study was performed in a three stepped program: site investigation and sampling, laboratory tests and concrete petrography. During the site inspection it was recognized that there was dissolution of the concrete in some sectors of the structure, with the aggregate particles protruding in relation to the undulated surface. In some places a white to yellowish putty-like product could be excavated by hand. The main deterioration was observed above the water level. The composition of the atmosphere inside the sewer was assessed and a high content of hydrogen sulfide was detected. Sampling was performed in different structural elements which showed diverse exposition to the aggressive environment. Impregnated thin sections of concrete with fluorescent yellow dye were analyzed by optical microscope. Concrete petrography showed to be crucial for the diagnoses. The study showed that the putty-like product was composed by gypsum with small residual particles of siliceous sand which resisted to the acid attack. SEM/EDS was used to evaluate the content of sulfur in different sections of the concrete cores and also to characterize the putty-like product at the surface of the concrete. This study led to the confirmation of the presence of an extensive sulfuric acid attack with rather minor sulfate attack within the concrete due to the exposition to aggressive environment. It also showed that behind the superficial deteriorated level, the concrete was sound with no signs of internal deleterious reactions. Ammonium content in residual water might have also contributed to the superficial deterioration of the concrete sewer.     

Probabilistic optimization of welded joints maintenance versus fatigue and fracture

This paper presents a probabilistic maintenance optimization procedure for welded joints damaged by fatigue. The linear elastic fracture mechanics stands as a basis for fatigue crack growth while the crack depth at failure is determined according to brittle or ductile fracture. The first order reliability method being applied, the assessment is then based on reliability indices. At an inspection instant, different events can occur: no crack detection, crack detection, and repair. All these events are uncertain and are expressed in terms of probabilities. As they are cost-dependent, the total expected cost of maintenance could be obtained. The inspection instant is therefore searched by minimizing that total expected cost. Such an approach appears as a good compromise between reliability and costs. The paper provides some sensitivity studies and an application on a real case.     

Assessing the Recyclability of Supramolecularly Assembled Organocatalytic Species: A Theoretical Insight

Asymmetric organocatalytic synthesis is a powerful tool in organic chemistry to achieve desired stereoisomers in high purity via mild catalytic routes. The immobilization of homogeneous catalytic species onto heterogeneous phases embodies the evolution of asymmetric catalysis, since it allows the recycling of the catalyst for several runs until degradation. Previously reported non-covalent immobilization of proline-based catalysts for aldol reaction onto magnetic nanoparticles functionalized with β-cyclodextrin (MNP-β-CB) demonstrated the viability of the methodology. This paper proposes two new catalyst recycling strategies based on Cucurbit[7]uril (CB[7]) for the aldol reaction and the Robinson annulation. These recycling methodologies are conceptually different. The former relies on the homogeneous encapsulation of the catalyst in cucurbituril, CB[7] ⋅ Cat, and its recycling in the aqueous phase by extraction of the aldol product with organic solvents. The latter relies on the heterogeneous encapsulation of the catalyst as MNP-CB[7] ⋅ Cat2 system and its recycling by magnetic harvesting. Density functional theory (DFT) calculations have been employed to rationalize the thermodynamics of experimental results, and to suggest caveats and plausible improvements in view of a future catalytic design.     

Efficient computation of the Zassenhaus formula

A new recursive procedure to compute the Zassenhaus formula up to high order is presented, providing each exponent in the factorization directly as a linear combination of independent commutators and thus containing the minimum number of terms. The recursion can be easily implemented in a symbolic algebra package and requires much less computational effort, both in time and memory resources, than previous algorithms. In addition, by bounding appropriately each term in the recursion, it is possible to get a larger convergence domain of the Zassenhaus formula when it is formulated in a Banach algebra.     

Antioxidant capacity and vasodilatory properties of Mediterranean food: The case of Cannonau wine,myrtle berries liqueur and strawberry-tree honey

The aim of this work was to use different assays to evaluate the antioxidant and vasodilatory properties of three typical food products from the Mediterranean area and to correlate these activities with their phenolic content. For this purpose, red wines Cannonau, liqueurs obtained by cold maceration of myrtle (Myrtus communis L.) berries and bitter honeys obtained from strawberry-tree flowers (Arbutus unedo L.) were analysed. The total phenolic (TP) content was measured spectrophotometrically with a modified Folin–Ciocalteau method and phenolic compounds were identified and dosed by HPLC-DAD and LC-MS/MS. Antioxidant activities were evaluated with DPPH, FRAP and ABTS assays and the in vitro vasodilatory effects were assessed using norepinephrine precontracted rat aortic rings. Cannonau wines and myrtle liqueurs showed high levels of TP (1978 ± 279 and 1741 ± 150 mg GAE/L, respectively), linearly correlated to the results of FRAP, ABTS, and DPPH assays. Their maximal vasodilatory activity was 61.7 ± 4.1% and 53.0 ± 3.0%, respectively. Although strawberry-tree honey contained relatively high levels of phenolic compounds (922 ± 38 mg GAE/kg), it did not induce vasodilation, even at the highest dose tested (0.206 g/L). These results indicate that foods with high levels of phenolic compounds should be studied using several different biological assays before being recommended to the general public as functional foods.     

Carbon diffusion in α-iron: Evidence for quantum mechanical tunneling

Recent experimental data on the diffusion coefficient of carbon in α-iron below the liquid nitrogen temperature (LNT) question the classical approach to the observed temperature dependence. As the temperature is lowered below the LNT, the diffusion constant tends toward a nearly temperature-independent value rather than continuing its activated trend. The low-temperature branch is apparently characteristic of a quantum mechanical process dominated by tunneling in the ground state. Concomitantly, we apply an occurrence-probability approach to describing the overall temperature dependence as a single continuous rate. Within the adiabatic approximation, the electronic eigen value, depending parametrically on the nuclear coordinates, is taken to be the potential energy to control the motion of the nuclei. The resulting rate involves all horizontal-tunneling energy-conserving elastic transitions at the quantized energy levels of the migrating atom. A small though not negligible slope in the temperature dependence as the temperature is raised below 100 K is dealt with by complementing for the rate of a parallel one-phonon inelastic-tunneling process in excess of the basic elastic-tunneling rate. Our combined approach agrees well with the experimental data. In particular, the frequency of the coupled vibration is obtained virtually identical to the carbon vibrational frequency from inelastic neutron scattering data. The migrational barrier is also found to be within the limits expected for α-iron.     

Automobile accidents in patients with sleep apnea syndrome. An epidemiological and mechanistic study

AIM: To compare the pregnancy outcome, in particular gestational age and birth weight in women with systemic lupus erythematosus (SLE) diagnosed before and after pregnancy, and to review data on presence or absence of the antiphospholipid (aPL) antibody and flares of disease activity. METHOD: Case histories were reviewed of women with a diagnosis of SLE and an obstetric event attending Monash Medical Centre (MMC) over an eight year period (1988-96). Fifty-four pregnancies in 28 women were studied, with 44 occurring after the diagnosis of SLE (Group 1) and ten prior to the diagnosis of SLE (Group 2). RESULTS: In Group 1 there were 25 live births (63%) with 16 full term and nine premature deliveries, 12 spontaneous abortions, three foetal deaths in utero and four elective terminations. In Group 2 there were seven live births (70%), two spontaneous abortions and one foetal death in utero. The mean gestational age of live births was 35.8 weeks and 39.2 weeks respectively (p < 0.001). The mean birth weight of live births was 2448 g and 3030 g respectively (p < 0.023). a PL antibodies were positive in eight of 26 women tested with three live births and were negative in 18 of 26 women with 12 live births. Flares of disease activity occurred in 17 of 28 pregnancies. CONCLUSION: Pregnancy in women with a predisposition to SLE have a high risk of an adverse outcome. Clinical disease confers an additional risk. The mean gestational age and birth weight were significantly less in women with established disease. Mild flares in disease activity resulted in a favourable outcome while renal flares had a worse outcome.     

Crystal Structure of Human Soluble Adenylate Cyclase Reveals a Distinct,Highly Flexible Allosteric Bicarbonate Binding Pocket

Soluble adenylate cyclases catalyse the synthesis of the second messenger cAMP through the cyclisation of ATP and are the only known enzymes to be directly activated by bicarbonate. Here, we report the first crystal structure of the human enzyme that reveals a pseudosymmetrical arrangement of two catalytic domains to produce a single competent active site and a novel discrete bicarbonate binding pocket. Crystal structures of the apo protein, the protein in complex with α,β‐methylene adenosine 5′‐triphosphate (AMPCPP) and calcium, with the allosteric activator bicarbonate, and also with a number of inhibitors identified using fragment screening, all show a flexible active site that undergoes significant conformational changes on binding of ligands. The resulting nanomolar‐potent inhibitors that were developed bind at both the substrate binding pocket and the allosteric site, and can be used as chemical probes to further elucidate the function of this protein.