Search

ASTM A213 T91 steel is widely used in power plants and petrochemical industry for long-term service components. Due to its high resistance to creep, thermomechanical fatigue and corrosion, the use of grade 91 steel allows usual plant service parameters to be raised up to ultra-supercritical conditions (600 °C, 300 bar) so that performances are remarkably increased. The strongest factors that affect performances are the time of exposure, the temperature and the applied stress: such parameters can dramatically decrease the service life of a plant component. The improved mechanical properties of grade 91 are strictly related to its specific microstructure: a tempered martensite matrix with fine precipitates embedded in. Two typologies of secondary phases are present: M23C6 carbides (where M = Cr/Fe/Mo/Mn) and finely dispersed MX-type carbonitrides (where M = V/Nb and X = C/N). This study is focused on the microstructure evolution of grade 91 steel under creep conditions. First, three sets of laboratory-aged specimens heated in oven at 550 °C, 600 °C and 650 °C were examined; the exposure time was up to 50,000 h. Furthermore, the influence of stress on the microstructure in two sets of samples was evaluated: a first batch of specimens cut from an ex-service tube of a petrochemical plant (over 100,000 h of service at 580 °C and 19–25 bar) and a second set of samples coming from another ex-service tube under ultra-supercritical conditions (605 °C, 252 bar) in a power plant. The microstructures were characterized by optical, scanning electron and transmission electron microscopy and the results were compared to the literature. Some interesting trends were evidenced, in terms of secondary phases precipitation and coarsening, as well as martensite recovery. Furthermore, the applied stress seems to influence size and number of Laves phase particles.

With the increasing interest in the potential benefits of nanotechnologies, concern is still growing that they may present emerging risks for workers. Various strategies have been developed to assess the exposure to nano-objects and their agglomerates and aggregates (NOAA) in the workplace, integrating different aerosol measurement instruments and taking into account multiple parameters that may influence NOAA toxicity. The present study proposes a multi-metric approach for measuring and sampling NOAA in the workplace, applied to three case studies in laboratories each dedicated to materials with different shapes and dimensionalities: graphene, nanowires, and nanoparticles. The study is part of a larger project with the aim of improving risk management tools in nanomaterials research laboratories. The harmonized methodology proposed by the Organization for Economic Cooperation and Development (OECD) has been applied, including information gathering about materials and processes, measurements with easy-to-use and hand-held real-time devices, air sampling with personal samplers, and off-line analysis using scanning electron microscopy. Significant values beyond which an emission can be attributed to the NOAA production process were identified by comparison of the particle number concentration (PNC) time series and the corresponding background levels in the three laboratories. We explored the relations between background PNC and microclimatic parameters. Morphological and elemental analysis of sampled filters was done to identify possible emission sources of NOAA during the production processes: rare particles, spherical, with average diameter similar to the produced NOAA were identified in the nanoparticles laboratory, so further investigation is recommended to confirm the potential for worker exposure. In conclusion, the information obtained should provide a valuable basis for improving risk management strategies in the laboratory at work.

ASTM A213 T91 steel is used in power plants and petrochemical industry, for long-term service components. The improved mechanical properties of grade 91 are strictly related to its specific microstructure: a tempered martensite matrix with fine precipitates embedded in. Despite low alloy heat resistant ferritic steels, that have a well known operational experience, T91 service performances are still faintly consolidated, because this material has serviced only in a limited number of plants, since the eighties. Most of the available data were obtained by laboratory tests on relatively short term creep strength and corrosion properties. The investigations reported in this paper represent an important opportunity to describe and better evaluate the damage evolution of the grade T91 steel after more than 100000 h of exposure in severe conditions (580 °C, 18–26 bar, combustion environment). Our results suggest that the steel suffered by different damage forms, which appear on definite portions of the tube cross section. The main degradation forms observed, in fact, into the tube bulk are both the martensite recovery and the microstructural evolution. This latter promoted mostly Laves phase precipitation and coarsening. On the other hand, both the outer and the inner wall side, suffered mainly by severe oxidation/carburization. Especially on the outer surface, the massive carbide precipitation has caused an evident loss of ductility so that the mechanical properties of the tube appear appreciably reduced.

After 10 years of service, one high-pressure cylinder made by 34CrMo4 low alloy steel fractured catastrophically, causing extensive damages. The cylinder was filled with a commercially available mixture of nitrogen, argon and carbon dioxide. A failure analysis has been carried out in order to identify the cause of rupture. The examination of cross sections specimens has revealed several branched cracks originating at cylinder inner wall side and propagating across the bulk. The observation of fracture surfaces supported the hypothesis of an environmental attack that affected the cylinder inner surface. No evidences of other damage form have been found: the chemical analysis, the microstructure examination and the mechanical tests performed provided results in full compliance with the technical specifications of the alloy. On the basis of such considerations, it can be assumed that the cylinder fractured by stress corrosion cracking. The exposition to a CO/CO 2 containing atmosphere in presence of undesired traces of moisture promoted the local damage, as long as the applied tensile stress triggered cracks formation and propagation. Then, a progressive reduction of the effective toughness occurred, leading to a sudden, catastrophic, overload rupture.

The scope and limitations of gold-catalyzed tandem cycloisomerization/fluorination reactions of unprotected 2-alkynylanilines to have access to 3,3-difluoro-2-aryl-3H-indoles and 3-fluoro-2-arylindoles are described. An unprecedented aminoauration/oxidation/fluorination cascade reaction of 2-alkynylanilines bearing a linear alkyl group on the terminal triple bond is reported.

A tandem gold(I)-catalyzed aminocylization/fluorination and a two-step, one-pot gold(III)-catalyzed cyclization/electrophilic fluorination provide a convenient and general method for the synthesis of 3,3-difluoro-2-substituted-3H-indoles in good yield under mild conditions. Extension of the procedure to the synthesis of 2-aryl-3-fluoro-1H-indoles is described. The reaction proceeds smoothly in green ethanol and does not require any base, acid, or N-protective group.

The Small Punch test is a miniaturized non-intrusive methodology that allows performing creep tests using very small specimens. It can be used for the residual lifetime assessment of in service components. In the last years, numerous applications of Small Punch Testing as well as related pre-normative work and Round Robin exercises have led to new insights which motivate a revision of the current Code of Practice for Small Punch Testing (CWA 15627, Dec. 2007) and/or its transfer in an EN norm. In this paper we present the state-of-art of the small punch technique: its performances, usefulness and critical aspects have been discussed and some examples have been reported. Some measurements carried out during the round-robin exercises have been reported: several testing laboratories are cooperating in a round-robin on a virgin P92 material. The tests are still in progress, so only preliminary data will be shown in this paper. A series of measurements performed during the pre-normative time will also be shown: a serviced (116,000 hours) ASME A213 T91 tube, installed in a petrochemical plant has been investigated. Small punch tests were performed and the residual life was then estimated by Omega Method. A microstructure characterization has been also reported. The results obtained encourage new efforts for material testing by SPT; sampling, however, was found as a critical step if the analyzed material may suffer from localized damage.

ASTM A 297 grade HP steels are widely employed for radiant tubes in reforming furnaces: this class of heat resistant alloys shows high creep and corrosion resistance, ensuring good performances in extreme pressure and temperature conditions. The typical microstructure of such materials is an austenitic matrix surrounded by a network of interdendritic carbides, which contain chromium and other carbide forming elements, namely Nb, Ti, W, Zr and Y. During long service life, these high strength materials may suffer aging or even severe damage, especially when process conditions allow coke deposition, or maintenance procedures are not carried properly. Service aging can be summarized, for HP steels, in terms of microstructure degradation: coalescence and coarsening of interdendritic precipitates, precipitation of secondary carbides in the austenite matrix and transformation of niobium-rich carbides in the G-phase silicide are the typical phenomena occurring on the microstructure of these alloys during service. Carburization can also occur in radiant tubes, since their inner wall side is exposed to hydrocarbon-rich process fluids: carbon diffuses into the metal matrix, causing massive precipitation of chromium-rich carbides. The alloy corrosion resistance is then reduced, resulting in surface attack, cracks development and a general wastage of the material. Furthermore, the high temperatures, which tubes are exposed to, can also induce creep, especially if a local tube overheating occurs: cavities and microcracks, mainly localized at precipitates, are the typical evidences of creep damage on HP steels. The present work is aimed on the damage characterization of several radiant tubes in HP alloys, after long term service aging in reforming plants. We employed optical and electron microscopy, EDX elements mapping and mechanical tests, in order to characterize and evaluate the various damages affecting the alloys. Microstructure evolution has been detected in all the analyzed tubes, but we found that such a phenomenon was strictly influenced by the chemical composition of each alloy, so that in presence of small amounts of titanium and tungsten, the chemical evolution of the secondary phases was appreciably contained. Creep also was observed in all the investigated tubes and its extent was found to be related to both alloy composition and process conditions. These latter have assumed to be the main driving factor for carburization, since we observed that slight differences in temperature, pressure, chemical composition of the process fluid and tube maintenance dramatically conditioned the performances of each tube. Massive precipitation and material degradation, in fact, were found in some cases, but, on the other side, no appreciable evidence of carburization damage was observed on other cases.

In this study, we reported the analysis of the medium polarity fraction obtained from an accession of Helichrysum microphyllum subsp. tyrrhenicum from La Maddalena Island. Besides several compounds already evidenced in this species and related genera, i.e. micropyrone (1), arzanol (2), helipyrone (3), acetyl-bitalin derivatives (4, 5), gnaphaliol (6), caffeic acid (7), ursolic acid (8), 7-O-β-(D-glucopyranosyl)-5-methoxy-1(3H)-isobenzofuranone (9), gnaphaliol-9-O-β-D-glucopyranoside (11) and gnaphaliol-3-O-β-D-glucopyranoside (12), the presence of a new glycosidic phthalide, 6-O-β-(D-glucopyranosyl)-4-methoxy-1(3H)-benzofuranone (10), was evidenced for the first time, which resulted in a structural isomer of compound (9). The occurrence of this new benzofuranone derivative is an additional evidence of the deep intraspecific variability expressed by this species, which was also stated for the non-volatile components, and may be a distinctive trait of the population growing on La Maddalena Island.

Taspine is an alkaloid found in the latex of certain trees belonging to the family of Euphorbiaceae, commonly called “Sangre de Drago” (Dragon's blood). Its structure and antineoplastic properties are well known. Here we report the total synthesis of taspine, starting from ferulic acid and isovanillin. The successful synthetic strategy was then applied to the synthesis of a symmetrical analogue TAS2C. Both the synthesised compounds were tested by ESI-MS (electrospray ionisation mass spectrometry) for their ability to bind different quadruplex and duplex DNA structures.

Reformer furnaces are used in petrochemical industry to produce hydrogen. Their most critical components are radiant tubes, where extreme temperature and pressure conditions required the deployment of high alloyed austenitic HP grade steels, owing to their superior strength to creep rupture and good corrosion resistance. Nevertheless, these high strength alloys undergo damage when process conditions allow coke deposition and maintenance procedures are not carried properly. Two radiant tubes, coming from two different plants and made of HP40Nb and HP40Nb microalloy steels respectively, are investigated here to highlight the endured damage after 85,000–96,000 h of service at maximum temperature of ∼950 °C. Light optical microscopy (LOM) and scanning electron microscopy (SEM) analyses both confirmed significant aging in both tubes, as revealed by a substantial microstructural evolution consisting of phases transformation and precipitation, as well as cavitation and incipient microcracking in the bulk. Mechanical testing demonstrated the considerable worsening of mechanical properties following such a microstructural deterioration. However, noticeable differences between the two tubes were discovered as far as type and distribution of damage, and extent of the aged zone. The small differences in alloys composition seem not sufficient alone to explain such dissimilarity in behaviour because, in addition to creep damage, one tube showed also clear evidence of carburization. Instead it is argued that differences in process conditions (i.e. temperature, pressure chemical composition of process fluids and steam–hydrocarbon ratio) and cleaning maintenance for decoking (i.e. type and frequency) may have synergistically triggered different damage mechanisms responsible for the different form of degradation on each reformer tube.

In this paper, we report an extensive electrospray ionization mass spectrometry (ESI-MS) study of the noncovalent interactions between different intermolecular and intramolecular G-quadruplex structures and several perylene and coronene ligands. The selectivity of these compounds toward quadruplex structures with respect to duplex DNA, a fundamental topic for the biological evaluation and the pharmacological application of these ligands as potential chemotherapeutic agents, has also been investigated. After exploring this topic according to the classical approach based on the very simple duplex model of an autocomplementary dodecamer, we extended our analysis reporting for the first time a competition ESI-MS experiment in the presence of genomic DNA fragments. Whereas those ligands showing a high level of selectivity between quadruplex and duplex oligonucleotides, in terms of binding constants and percentage of bound DNA, confirmed their selectivity in the competition experiment, the contrary was not always true: some ligands showing poor selectivity with the autocomplementary dodecamer resulted selective in the presence of genomic DNA fragments. This result suggests that physiologically nonrelevant interactions are possible with a short duplex oligonucleotide. This means that the dodecamer can fail in representing a biologically significant structural model, or, better, that it can be used to quickly screen potentially selective molecules, but bearing in mind the high probability of false negative results.

Four new perylene derivatives with three and four basic side-chains are reported here as G-quadruplex interactive compounds. The new perylene derivatives are readily soluble in water and not self-aggregated, in contrast to what happens with the previously reported two side-chain perylene derivatives. All four compounds are able to induce the G-quadruplex and to inhibit 50% of telomerase activity at about 5 microM concentration, showing a similar efficiency with respect to each other. Molecular modelling studies are presented to try to explain these findings.

In developing G-quadruplex interactive telomerase inhibitors two main features have to be taken into account: the hydrophobic interactions with the G-quartet plane and the electrostatic interactions with the negatively charged phosphates of the four grooves. In this paper, we report the synthesis of four hydrosoluble coronene derivatives, which are characterized by a large hydrophobic aromatic core and four orthogonal hydrophilic side chains. We have studied their ability to induce both inter- and intramolecular G-quadruplex structures and found a significant selectivity of all the coronene derivatives for the intramolecular G-quadruplex. The efficiency in inhibiting human telomerase has been evaluated in a cell-free system and the experimental results correlate with the relative affinities of these compounds for the G-quadruplex monomeric structure, as derived by molecular modelling simulations. Thus, the coronene derivatives can be considered as a new class of telomerase inhibitors, although further investigations are surely necessary to fully exploit their features.

Several lipophilic perylene and coronene derivatives, employed mainly as liquid crystalline dyes are known and their synthesis has been widely studied. We have applied an analogue strategy using hydrophilic substituents to obtain highly water soluble perylene diimides (4) and a new hydrosoluble coronene derivative (CORON, 6), whose molecular features appear particularly suitable for inducing G-quadruplex DNA structures and inhibiting human telomerase.

A tandem gold(I)-catalyzed aminocylization/fluorination and a two-step, one-pot gold(III)-catalyzed cyclization/electrophilic fluorination provide a convenient and general method for the synthesis of 3,3-difluoro-2-substituted-3H-indoles in good yield under mild conditions. Extension of the procedure to the synthesis of 2-aryl-3-fluoro-1H-indoles is described. The reaction proceeds smoothly in green ethanol and does not require any base, acid, or N-protective group.

Following previous studies on anthraquinone and acridine-based G-quadruplex ligands, here we present a study of similar aromatic cores, with the specific aim of increasing G-quadruplex binding and selectivity with respect to duplex DNA. Synthesized compounds include two and three-side chain xanthone and xanthene derivatives, as well as a dimeric “bridged” form. ESI and FRET measurements suggest that all the studied molecules are good G-quadruplex ligands, both at telomeres and on G-quadruplex forming sequences of oncogene promoters. The dimeric compound and the three-side chain xanthone derivative have been shown to represent the best compounds emerging from the different series of ligands presented here, having also high selectivity for G-quadruplex structures with respect to duplex DNA. Molecular modeling simulations are in broad agreement with the experimental data.

Based on previous work on both perylene and coronene derivatives as G-quadruplex binders, a novel chimeric compound was designed: N,N′-bis[2-(1-piperidino)-ethyl]-1-(1-piperidinyl)-6-[2-(1-piperidino)-ethyl]-benzo[ghi]perylene-3,4:9,10-tetracarboxylic diimide (EMICORON), having one piperidinyl group bound to the perylene bay area (positions 1, 12 and 6, 7 of the aromatic core), sufficient to guarantee good selectivity, and an extended aromatic core able to increase the stacking interactions with the terminal tetrad of the G-quadruplex. The obtained “chimera” molecule, EMICORON, rapidly triggers extensive DNA damage of telomeres, associated with the delocalization of telomeric protein protection of telomeres 1 (POT1), and efficiently limits the growth of both telomerase-positive and -negative tumor cells. Notably, the biological effects of EMICORON are more potent than those of the previously described perylene derivative (PPL3C), and more interestingly, EMICORON appears to be detrimental to transformed and tumor cells, while normal fibroblasts expressing telomerase remain unaffected. These results identify a new promising G-quadruplex ligand, structurally and biologically similar on one side to coronene and on the other side to a bay-monosubstituted perylene, that warrants further studies.

Telomerase is responsible for the immortal phenotype of cancer cells and telomerase inhibition may specifically target cancer cell proliferation. Ligands able to selectively bind to G-quadruplex telomeric DNA have been considered as telomerase inhibitors but their mechanisms of action have often been deduced from a non-quantitative telomerase activity assay (TRAP assay) that involves a PCR step and that does not provide insight on the mechanism of inhibition. Furthermore, quadruplex ligands have also been shown to exert their effects by affecting association of telomere binding proteins with telomeres. Here, we use quantitative direct telomerase activity assays to evaluate the strength and mechanism of action of hydrosoluble perylene diimides (HPDIs). HPDIs contain a perylene moiety and different numbers of positively charged side chains. Side chain features vary with regard to number and distances of the charges. IC50 values of HPDIs were in the low micromolar (0.5-5 mu M) range depending on the number and features of the side chains. HPDIs having four side chains emerged as the best compounds of this series. Analysis of primer elongation products demonstrated that at low HPDI concentrations, telomerase inhibition involved formation of telomeric G-quadruplex structures, which inhibited further elongation by telomerase. At high HPDI concentrations, telomerase inhibition occurred independently of G-quadruplex formation of the substrate. The mechanism of action of HPDIs and their specific binding to G-quadruplex DNA was supported by PAGE analysis, CD spectroscopy and ESI-MS. Finally, competition Telospot experiments with duplex DNA indicated specific binding of HPDIs to the single-stranded telomeric substrates over double stranded DNA, a result supported by competitive ESI-MS. Altogether, our results indicate that HPDIs act by stabilizing G-quadruplex structures in single-stranded telomeric DNA, which in turn prevents repeat addition processivity of telomerase. (C) 2011 Elsevier Masson SAS. All rights reserved.

A series of bay-substituted perylene derivatives is reported as a new class of G-quadruplex ligands. The synthesized compounds have differing N-cyclic substituents on the bay area and differing side chains on the perylene major axis. ESI-MS and FRET measurements highlighted the strongest quadruplex binders in this series and those showing the highest quadruplex/duplex selectivity. Several biological assays were performed on these compounds, which showed that compound 5 (PPL3C) triggered a DNA damage response in transformed cells with the formation of telomeric foci containing phosphorylated γ-H2AX and 53BP1. This effect mainly occurred in replicating cells and was consistent with Pot1 dissociation. Compound 5 does not induce telomere damage in normal cells, which are unaffected by treatment with the compound, suggesting that this agent preferentially kills cancer cells. These results reinforce the notion that G-quadruplex binding compounds can act as broad inhibitors of telomere-related processes and have potential as selective antineoplastic drugs.

Complexation of Zn(II) ions by cyclam cored dendrimers appended with four (G0), eight (G1) and 16 naphthyl chromophores (G2) at the periphery have been investigated in CH3CN-CH2Cl2 1 : 1 (v/v) solution by absorption and emission, ESI-mass and H-1 NMR spectroscopy. The results obtained can be interpreted by the formation of complexes of 2 : 1 dendrimer to metal stoichiometry, at low metal ion concentration, and 1 : 1 complexes upon further addition of Zn(II) ions, for all the dendrimer generations. Upon addition of a molecular clip C2- consisting of two anthracene sidewalls bridged by a benzene group with two sulfate substituents in the para positions, heteroleptic complexes of general formula [GnZnC] are formed. Interestingly, in these complexes, a very efficient quenching (practically 100%) of the dendrimer naphthyl luminescence and sensitization (ca. 90%) of the clip anthracene emission take place. The complex [G2ZnC] exhibits a very high molar absorption coefficient in the UV spectral region owing to the 16 naphthyl chromophores of the dendrimer and the two anthracene units of the clip (epsilon = 1.7 x 10(5) M-1 cm(-1) at 263 nm). Furthermore, the excitation energy absorbed by the naphthyl chromophores is efficiently funneled to the two anthracene units of the clip, which emits in the blue spectral region.

Triazatruxene derivatives find many applications as lipophilic compounds, but few examples of hydrosoluble derivatives have been reported so far. In this paper, we compare different synthetic routes for the preparation of hydrophilic triazatruxene derivatives and define the most versatile pathway. The synthesized compounds are fluorescent not only in organic solvents, as reported for other lipophilic derivatives, but also in water, making them particularly suitable for biological applications.

Most known perylene diimides are lipophilic, with few exceptions of hydrophilic derivatives. Even in the latter case, the compounds have limited water solubility and show a strong tendency to self-aggregation. In this paper we present the synthesis of four new perylene derivatives with three and four basic side chains, obtained by functionalizing the bay-area of perylene. These molecules show great solubility in aqueous media as hydrochlorides and their tendency to self-aggregate is remarkably reduced with respect to the previously synthesized two-chained perylene diimides. Their different spectroscopic properties in various solvents and conditions are reported and discussed.