Surface and volume non-invasive methods for the structural monitoring of the bass-relief ‘Madonna con Bambino’ (Gorizia,Northern Italy)

Abstract

Structural analysis of marble statues, carried out by non-invasive and in situ methods, is crucial to define the state of conservation of the artworks and to identify the deterioration phenomena that can affect them. In this work, we combined in situ non-destructive techniques, ultrasonic tomography (US), ultraviolet-induced visible fluorescence (UV-IF) and X-ray fluorescence (XRF) to study the bass-relief ‘Madonna con Bambino’ (Gorizia, Italy). The US revealed the presence of some metallic pivots, associated with areas of high sound velocity; moreover, a more degraded area has been identified in the lower part of the bass-relief. The acquired UV-IF image confirmed the presence of surface degradation, allowing a preliminary evaluation of the extension of a fracture, from surface to bulk. In addition, the different materials (both original and/or integrations) that compose the studied surface have been identified. The XRF has contributed to define the nature of the inorganic materials applied during undocumented previous restoration works on the surface as filler for lacunae.     

Degradation of Phosphorylated Poly(N-Vinylcarbazole) by Thermogravimetry ‡

Abstract

The thermal degradation of phosphorylated poly(N-vinylcarbazole) was studied by thermogravimetry. The onset degradation temperature decreases with respect to that of unmodified poly(N-vinylcarbazole), indicating a lower thermal stability for the phosphorylated sample. The activation energy values for the degradation process were calculated from the thermograms by treating it as a kinetic analysis; these values are smaller than those for unmodified samples and depend on molecular weight, phosphorous contents, and heating rate.     

Full Non-rigid Group of Sponge and Pina

The non-rigid molecule group theory (NRG) in which the dynamical symmetry operations are defined as physical operations is a new field in chemistry. Smeyers and Villa computed the r-NRG of the triple equivalent methyl rotation in pyramidal trimethylamine with inversion and proved that the r-NRG of this molecule is a group of order 648, containing a subgroup of order 324 without inversions (see J. Math. Chem. 28(4) (2000) 377–388). In this work, a computational method is described, by means of which it is possible to calculate the symmetry group of molecules. We study the full non-rigid group (f-NRG) of Sponge and Pina molecules with C ₂ and C _i point groups, respectively. It proved that these are groups of order 162 and 13122 with 54 and 3240 conjugacy classes, respectively. The character tables of these groups are also computed.     

Technical-scientific investigations to detect the temporal vicissitudes of the funeral monument of Innocent VIII (Giovanbattista Cibo, 1484–1492), compared with that of Sixtus IV (Francesco della Rovere 1471–1484), both made by Antonio del Pollaiolo

Abstract

The restoration of the funeral monument of Innocent VIII (Giovan-Battista Cibo, 1484–1492) was executed by Sante Guido with the support of the Knights of Columbus. The praiseworthy intervention aimed at restoring the monument from polluting aerodynamic agents has at the same time enabled a careful study of the work regarding, above all, the authenticity of the current coloring in relation to the original presentation intended by Antonio del Pollaiolo. In particular, an attempt has been made to uncover the historical vicissitudes of the work: from its realization to the present restoration. In this regard, I would like to recall that, as reported by Pasquale Rotondi, the restoration of a work is a very special moment in which it is possible to carry out all the studies aimed at understanding the causes which have determined its state of conservation, as well as, of course, its constituent elements and its implementing methods.     

Flammability and Thermal Oxidative Degradation Kinetics of Magnesium Hydroxide and Expandable Graphite Flame Retarded Polypropylene Composites

The flammability and the thermal oxidative degradation kinetics of expandable graphite (EG) with magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results show that EG is a good synergist for improving the flame retardancy of PP/MH composite and the effect is enhanced with decreasing EG particle size. The Kissinger method and Flynn‐Wall‐Ozawa method were used to determine the apparent activation energy (E) for degradation of PP and flame retarded PP composites. The data obtained from the TGA curve indicate that EG markedly increases the thermal degradation temperature of PP/MH composites and improves the thermal stability of the composites. The kinetic results show that the values of E for degradation of flame retarded PP composites is much higher than that of neat PP, especially PP/MH composites with suitable amount of EG, which indicates that the flame retardants used in this work have a great effect on the mechanisms of pyrolysis and combustion of PP.     

A High-Performance Liquid Chromatography Study of D-Cellobiose Degradation Under Fenton Conditions

Abstract

Cellobiose was used to model chemical processes taking place during the weathering of cotton fiber cellulose. High-performance liquid chromatography (HPLC) showed that the products of cellobiose degradation were D-glucose and organic acids under Fenton-type conditions (ferrous ion plus H₂0₂). Hydrogen peroxide was added directly or photochemically generated in situ by the action of UV light upon aqueous ferrous ammonium sulfate. Effects on D-cellobiose degradation caused by added peroxide or ferrous ion were nonitored at varying concentrations and under UV light and dark conditions. Increasing concentrations of peroxide or ferrous ion resulted in greater degradation. Samples exposed to UV light (350 nm) experienced greater degradation than those not exposed.     

Sphaerococcus coronopifolius (Rhodophyta,Gigartinales): a Mediterranean red alga with potential and applications in restoration

Abstract

Experimental studies conducted on some species of Mediterranean red algae allowed to identify Sphaerococcus coronopifolius Stackhouse as a valid alternative to the Pacific alga Gloiopeltis furcata (Postels & Ruprecht) J. Agardh, for the extraction of a material usable as natural consolidant and adhesive in the field of restoration. Promising results have been observed by comparing the extracts obtained from these two algae after the same extraction procedure. Chemical analysis (FTIR) revealed that S. coronopifolius has qualities similar to G. furcata. Even more promising results for S. coronopifolius compared to G. furcata were observed after the analysis of pH and conductivity, and the adhesion tests carried out on both extracts.     

Thermal behavior of some N,N-dimethylbiguanide derivatives displaying antimicrobial activity

N,N-Dimethylbiguanide derivatives (HDMBG)X, where X=CH₃COO (1), Cl (2) and NO₃ (3) respectively, exhibit in vitro antimicrobial activity on representative bacterial and fungal strains. The presence of N,N-dimethylbiguanidium ion for all derivatives was evidenced by IR and ¹H NMR spectra. Thermal analysis gave information on their decomposition steps and also on the accompanying thermodynamic effects. According to TG and DTG curves processes as melting, oxidative degradation as well as oxidative condensation of –C=N– units occur. The different nature of the anions results different melting points. Paracyanide formation at various condensation degrees was observed.     

Application of microemulsions for the removal of synthetic resins from paintings on canvas

Abstract

Traditional cleaning methods with organic solvents often are not suitable for removal of aged resin so researchers have to find new formulations. In this work, a case study is reported in which new microemulsions were applied on the surface of a painting covered by some aged resin layers used during a previous restoration. Based on the quality of the intervention and the analysis of a sample of the varnish carried out with both MALDI-TOF and ATR-IR spectrometers, it was conjectured that this undesired material could be an acrylic polymer. So it was chosen to use xylene, ethyl acetate and propylene carbonate (XYL and EAPC) microemulsions (O/W oil in water). The first is able to solubilise only acrylic polymers, the second may solve both acrylic and vinyl resins. The first has had the greatest effect allowing complete varnish removal and original artwork restoration.     

Synthesis of new aromatic polyamides containing α-amino phosphonate with high thermal stability and low heat release rate

The new aromatic polyamides containing α-amino phosphonate were synthesized from phosphorus-based dicarboxylic acid 4 and various aromatic diamines by direct polycondensation reaction. Dicarboxylic acid 4 was successfully synthesized from trimethyl phosphite, 4-aminobenzoic acid and terephthaldehyde via a three-component reaction. The polymerization reaction produced the polyamides 6a–f with high yield and desirable inherent viscosities. The thermal properties of the all samples were investigated by thermo-gravimetric analysis (TGA). The TGA results in N₂ exhibited the 10% mass loss temperatures (T₁₀) in the ranges of 324–345 °C, while the T₁₀ resulted from thermo-oxidative degradation were higher than those. The main data obtained by microscale combustion calorimetry revealed acceptable combustion properties such as very low peak of heat release rate for the synthesized polyamides 6a–f. The all of the results indicated that these polyamides can be potentially utilized as additive for improvement of thermal resistance and combustion behavior of thermoplastic materials.

     

Dioxidouranium isothiosemicarbazone coordination compounds: synthesis,characterization, crystal structure,and thermal behavior

Five uranium complexes with UO₂L′(solv) formula (L′: prepared by condensation reaction between 2-hydroxyacetophenon S-pentyl isothiosemicarbazone (H₂L) and 5-bromosalicylaldehyde (Sal); solv: ethanol (1), 2-propanol (2), 2-butanol (3), ethylene glycol (4), 1,2-propanediol (5)) were synthesized through template reactions between H₂L, Sal, and UO₂(CH₃COO)₂?2H₂O for 1 and recrystallization of 1 in appropriate solvents for the other complexes. The compounds are characterized by melting point, elemental analyses, FT-IR, ¹H NMR, ¹³C NMR, TGA, and X-ray crystallography. Molecular structures of the obtained crystals, determined by X-ray diffraction analysis, showed that the complexes have distorted pentagonal bipyramidal geometry. In all complexes, the bianionic tetradentate ligand (N₂O₂) with phenolic oxygens (O3, O4), thioamidic and azomethine nitrogen donor atoms is coordinated to the metal center in equatorial positions and the solv molecules occupied the fifth equatorial site and finally linear UO₂ is located in axial position. The thermal behavior of the complexes was studied with TGA and DTG data and the results revealed three weight loss stages. The Coats–Redfern method is used for all degradation steps to determine kinetic parameters.     

Synthesis, structures, and properties of 3,6-di-tert-butyl-o-benzosemiquinone complexes of copper(i) with 1,5-diaza-3,7-diphosphacyclooctanes

Two new 3,6-di-tert-butyl-o-benzosemiquinone complexes of copper(i) (2a and2b) with 1,3,5,7-tetraphenyl-1,5-diaza-3,5-diphosphacyclooctane (1a) and 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane (1b), respectively, were synthesized. Their structures in solution and in the crystalline state were studied. According to the results of X-ray diffraction analysis, the copper(i) atom in molecules2a and2b is in a pseudotetrahedral environment and is directly coordinated to two P atoms of the diazadiphosphacyclooctane ligand and two O atoms of the benzosemiquinone ligand. In complex2a, ligand1a adopts a chair-boat conformation typical of all complexes with eight-membered cyclic 1,5-donors studied previously. Unlike ligand1a, the ligand in complex2b adopts a chair-chair (crown) conformation identical with that of the free ligand. Both complexes are paramagnetic in the solid state and in solutions. The parameters of the isotropic ESR spectra of complexes2a and2b are typical of four-coordinateo-semiquinone copper(i) complexes with bidentate bisphosphine ligands. Based on analysis of the isotropic ESR spectra, it was suggested that compound2b in solutions exists as two isomers, which differ in the conformation of the eight-membered heterocycle (chair-boat or chair-chair). Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1806–1812, October, 2000.     

Thermal behavior of some new triazole derivative complexes

A series of new complexes with mixed ligands of the type [ML(C₃H₃O₂)₂]·nH₂O (((1) M=Mn, n=1; (2) M=Co(II), n=2; (3) M=Ni(II), n=4; (4) M=Cu(II), n=1.5; (5) M=Zn(II), n=0; L=3-amino-1,2,4-triazole and (C₃H₃O₂)=acrylate anion) were synthesized and characterised by chemical analysis and IR data. In all complexes the 3-amino-1,2,4-triazole acts as bridge while the acrylate acts as bidentate ligand except for complex (5) where it is found as unidentate. The thermal behaviour steps were investigated in nitrogen flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion and 3-amino-1,2,4-triazole degradation respectively. The final products of decomposition are the most stable metal oxides, except for complex (4) that leads to metallic copper.     

New analogs of temporin-LK1 as inhibitors of multidrug-resistant (MDR) bacterial pathogens

The peptide temporin-LK1 (1) was obtained from the skin secretion of frog Limnonectes kuhlii (Ranidae). It is a unique antimicrobial peptide with 17 residues, including four L-phenylalanines and single glycine. Mass spectrometry and Edmand degradation were used for the determination of sequence of amino acids in temporin-LK 1 (1), and confirmed by cDNA cloning. We report here the synthesis and structural studies of temporin-LK1 (1) and its analogs 2–4. Peptides 2–4 were prepared by substitution of achiral glycine residue of temporin-LK1 (1) with D-alanine, L-phenylglycine, and L-naphthylalanine, respectively. Peptides 1–4 were evaluated against multidrug-resistant (MDR) strains of Staphylococcus aureus and Pseudomonas aeruginosa. Analog 2 was found active against all MDR strains of S. aureus and P. aeruginosa at a much lower dose than the clinically used antibiotics.     

The Photolysis of Polyvinylpyrrolidone in Aqueous Solutions in the Presence of Oxygen and Cupric Ions

Abstract

The oxidative photolysis of polyvinylpyrrolidone with light of λ = 2537 Å has been studied over a range of oxygen pressures and polymer concentrations. The results show that chain scission and cross linking take place simultaneously. In the range where cross linking is a negligible component, a mechanism based on chain scission due to components which lead to chain scission without intervention of oxygen, and a component which leads to chain scission via hydroperoxide side groups, has been proposed. This mechanism accounts satisfactorily for all observed features of the reaction. The degree of degradation at any one time decreases with oxygen pressure. Cupric ions, with or without oxygen present, have very little influence on the degradation process. However, the UV spectra of PVP in the presence of cupric ions are different from those without them.     

Thermal degradation behavior of some ruthenium complexes with fluoroquinolone derivatives as potential antitumor agents

Three new complexes with ligands belong to the fluoroquinolone class having the general formula [RuL₂Cl₂]Cl nH₂O ((1) L: norfloxacin (nf), n = 4; (2) L: ciprofloxacin (cp), n = 3; (3) L: enrofloxacin (enro), n = 5) were synthesized and characterized by chemical analysis UV–Vis and IR spectroscopy. In all complexes fluoroquinolone derivative acts as bidentate chelate ligand. The thermal behavior steps were investigated in synthetic air flow. The thermal transformations are complex processes according to TG and DTG curves including dehydration, quinolone derivative degradation, as well as RuCl₃ conversion in RuO₂.     

A new curvularin glycoside and its cytotoxic and antibacterial analogues from marine actinomycete Pseudonocardia sp. HS7

Five curvularin macrolides (1–5) were isolated from the cultured broth of marine actinomycete Pseudonocardia sp. HS7 that was obtained from the cloacal aperture of sea cucumber Holothuria moebii. The structures of these isolates were characterized as (11S,15R)-11-hydroxycurvularin (1), (11R,15R)-11-hydroxycurvularin (2), curvularin-7-O-α-D-glucopyranoside (3), trans-dehydrocurvularin (4) and curvularin (5) based on their NMR and HRESIMS data as well as chemical degradation. Compound 3 is a new macrolide with a rare α-D-glucopyranose substituent. Compounds 1–4, 5a and 5c (the acyl products of 5), suppressed the proliferation of all six tested cancer cell lines and 4 is the most active compound with IC₅₀ values ranging from 0.59 to 3.39 μM. The 11-hydroxycurvularins 1 and 2 also showed antibacterial activity inhibiting the growth of Escherichia coli.     

Biodegradation of Polycaprolactone by Microorganisms from an Industrial Compost of Household Refuse. Part II

Abstract

The rate of biodegradation of polycaprolactone samples, hydroxy (M _n = 4000 and 37000) and methoxy (M _n = 4000) terminated, by mixed cultures of microorganisms from a suspension of compost, and by a pure culture of an actinomycete isolated from it, has been monitored by the measurement of oxygen consumption. The dependence on polymer molecular weight suggests that initiation of degradation occurs in the vicinity of chain ends. Further analysis of the residues allows primary considerations about the bacterial metabolism of the substrate.     

Comparative isoconversional thermal analysis of Artemisia vulgaris hydrogel and its acetates; a potential matrix for sustained drug delivery

Abstract

Artemisia vulgaris hydrogel (AVH) was acetylated (AAVH) and characterized by FTIR, CP/MAS ¹³C-NMR spectroscopic techniques and thermogravimetric analysis. Flynn–Waal–Ozawa model was used to investigate thermal degradation kinetics. Energy of activation (Ea) values of first and major thermal degradation steps were found to be 128.14 and 116.85 kJmol^?1 for AVH and AAVH, respectively. Thermodynamic triplet, order of degradation reaction, integral procedural decomposition temperature (IPDT) and comprehensive index of intrinsic thermal stability (ITS) were also taken into account. In vitro caffeine release from AVH-based matrix tablets indicates potential of AVH for the development of oral delivery systems for sustained drug release.     

Two multifunctional organic-inorganic hybrid complexes based on polyoxometalates,BiEDTA and sodium linker: crystal structures,photochromic, and catalytic performances

Two 3-D organic–inorganic hybrid supermolecular complexes, Na(BiHEDTA·2H₂O)₃(PW₁₂O₄₀)·2H₃O (BiPW) and Na(BiHEDTA·2H₂O)₃(PMo₁₂O₄₀)·2H₃O·2H₂O (BiPMo) ethylenediamine tetraacetic acid (EDTA) have been synthesized by solution method and characterized by ultraviolet visible (UV–vis) spectroscopy, thermogravimetric-differential thermal analysis, photoluminescence, cyclic voltammetry, and single-crystal X-ray diffraction (XRD). XRD analysis reveals that BiPW and BiPMo are isostructural with 3-D architectures assembled by 2-D layer tetranuclear cation and a Keggin-type polyoxoanion. Although these two hybrids exhibit similar structures, the properties depend on the nature of polyoxoanion [PM₁₂O₄₀]^3? (M = W, Mo). Under UV irradiation, BiPW and BiPMo show fast response of reversible and irreversible photochromism, respectively. BiPW exhibits excellent photocatalytic activity in degradation of methyl orange dyes under irradiation of UV–visible light. It can be reused for at least six cycles without obvious loss of activity in the degradation experiments; BiPMo shows catalytic activity in elimination of methanol. The elimination rate of methanol reaches 56.9% when the concentration of methanol is 2.3 g·m^?3 and the flow velocity is 10 mL·min^?1 at 100 °C.