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Strongly degraded cellulosic artworks usually need deacidification and consolidation. Alkaline nanoparticles are known to be effective in neutralizing the acidity, while cellulose ...nanocrystals have the potential to be used as compatible and effective strengthening agents.
We have grafted cellulose nanocrystals with oleic acid using a 1′1-carbonyldiimidazole-mediated procedure, to increase their dispersibility in organic solvents, and synthesized Ca(OH)2 or CaCO3 nanoparticles via a solvothermal process. Grafted nanocellulose and alkaline nanoparticles were used to prepare ethanol-based “hybrids”. Prior to the application, the physico-chemical properties of nanocellulose dispersions and “hybrids” were studied by rheology and small-angle X-ray scattering.
Cellulose nanocrystals were effectively grafted and stably dispersed in ethanol. It was shown that the use of ethanol as a dispersing medium, and the addition of alkaline nanoparticles act in a synergistic way, increasing the interactions between grafted cellulose nanocrystals, leading to the formation of clusters. These dispersions are thixotropic, a behavior particularly appealing to conservation purposes, since they can be applied in the liquid state, or, when a more confined application is required, they can be applied in a gel-like state. As a result of the application, an improvement in the mechanical properties of paper and an increase of pH were obtained.
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The reaction of Ca(OH)2 with CO2 to form CaCO3 (carbonation process) is of high interest for construction materials, environmental applications and art preservation. Here, the ...“Boundary Nucleation and Growth” model (BNGM) was adopted for the first time to consider the effect of the surface area of Ca(OH)2 nanoparticles on the carbonation kinetics.
The carbonation of commercial and laboratory-prepared particles’ dispersions was monitored by Fourier Transform Infrared Spectroscopy, and the BNGM was used to analyze the data. The contributions of nucleation and growth of CaCO3 were evaluated separately.
During carbonation the boundary regions of the Ca(OH)2 particles are densely populated with CaCO3 nuclei, and transform early with subsequent thickening of slab-like regions centered on the original boundaries. A BNGM limiting case equation was thus used to fit the kinetics, where the transformation rate decreases exponentially with time. The carbonation rate constants, activation energies, and linear growth rate were calculated. Particles with larger size and lower surface area show a decrease of the rate at which the non-nucleated grains between the boundaries transform, and an increase of the ending time of Ca(OH)2 transformation. The effect of temperature on the carbonation kinetics and on the CaCO3 polymorphs formation was evaluated.
Background
Asparaginase is a critical component of lymphoblastic leukemia therapy, with intravenous pegaspargase (PEG) as the current standard product. Acute adverse events (aAEs) during PEG infusion ...are difficult to interpret, representing a mix of drug‐inactivating hypersensitivity and noninactivating reactions. Asparaginase Erwinia chrysanthemi (ERW) is approved for PEG hypersensitivity, but is less convenient, more expensive, and yields lower serum asparaginase activity (SAA). We began a policy of universal premedication and SAA testing for PEG, hypothesizing this would reduce aAEs and unnecessary drug substitutions.
Procedure
Retrospective chart review of patients receiving asparaginase before and after universal premedication before PEG was conducted, with SAA performed 1 week later. We excluded patients who had nonallergic asparaginase AEs. Primary end point was substitution to ERW. Secondary end points included aAEs, SAA testing, and cost.
Results
We substituted to ERW in 21 of 122 (17.2%) patients pre‐policy, and 5 of 68 (7.4%) post‐policy (RR, 0.427; 95% CI, 0.27–0.69, P = 0.028). All completed doses of PEG yielded excellent SAA (mean, 0.90 units/mL), compared with ERW (mean, 0.15 units/mL). PEG inactivation post‐policy was seen in 2 of 68 (2.9%), one silent and one with breakthrough aAE. The rate of aAEs pre/post‐policy was 17.2% versus 5.9% (RR, 0.342; 95% CI, 0.20–0.58, P = 0.017). Grade 4 aAE rate pre/post‐policy was 15% versus 0%. Cost analysis predicts $125 779 drug savings alone per substitution prevented ($12 402/premedicated patient).
Conclusions
Universal premedication reduced substitutions to ERW and aAE rate. SAA testing demonstrated low rates of silent inactivation, and higher SAA for PEG. A substantial savings was achieved. We propose universal premedication for PEG be standard of care.
Modern and contemporary art materials are generally prone to irreversible colour changes upon exposure to light and oxidizing agents. Graphene can be produced in thin large sheets, blocks ultraviolet ...light, and is impermeable to oxygen, moisture and corrosive agents; therefore, it has the potential to be used as a transparent layer for the protection of art objects in museums, during storage and transportation. Here we show that a single-layer or multilayer graphene veil, produced by chemical vapour deposition, can be deposited over artworks to protect them efficiently against colour fading, with a protection factor of up to 70%. We also show that this process is reversible since the graphene protective layer can be removed using a soft rubber eraser without causing any damage to the artwork. We have also explored a complementary contactless graphene-based route for colour protection that is based on the deposition of graphene on picture framing glass for use when the direct application of graphene is not feasible due to surface roughness or artwork fragility. Overall, the present results are a proof of concept of the potential use of graphene as an effective and removable protective advanced material to prevent colour fading in artworks.A single or multilayer graphene veil grown by chemical vapour deposition can be used to protect artworks against colour fading, with a protection factor of up to 70%.
In this paper, we propose a new algorithm for the segmentation of multiresolution remote-sensing images, which fits into the general split-and-merge paradigm. The splitting phase singles out clusters ...of connected regions that share the same spatial and spectral characteristics. These clusters are then regarded as atomic elements of more complex structures, particularly textures, that are gradually retrieved during the merging phase. The whole process is based on a recently developed hierarchical model of the image, which accurately describes its textural properties. In order to reduce the computational burden and preserve contours at the highest spatial definition, the algorithm works on the high-resolution panchromatic data first, using low-resolution full spectral information only at a later stage to refine the segmentation. It is completely unsupervised, with just a few parameters set at the beginning, and its final product is not a single segmentation map but rather a sequence of nested maps which provide a hierarchical description of the image, at various scales of observations. The first experimental results, obtained on a remote-sensing Ikonos image, are very encouraging and confirm the algorithm potential.
Alkaline earth metal hydroxide nanoparticles dispersions have demonstrated to be efficient for the preservation of cellulose-based artifacts, providing a stable neutral environment and, if in excess, ...turning into mild alkaline species. New formulations tailored for specific conservation issues have been recently obtained via a solvothermal reaction, starting from bulk metal, and short chain alcohols. Using this synthetic procedure, stable, and high concentrated calcium hydroxide nanoparticles dispersions can be obtained. The characterization of nanoparticles was carried out by dynamic light scattering, transmission electron microscopy and X-ray powder diffraction and showed that the dispersed systems are particularly suitable for the application on porous substrates. In a direct application of this technology, acidic paper and canvas samples were artificially aged after deacidification using calcium hydroxide nanoparticles dispersed in short chain alcohols. Cellulose viscosimetric polymerization degree (DPv), cellulose pyrolysis temperature, and samples’ pH were evaluated upon the aging and in terms of protective action arising from the applied treatment. In particular, determinations of DPv clearly showed that the degradation of acidic paper and canvas samples proceeds at higher rates with respect to deacidified samples. These evidences were also confirmed by the thermogravimetric analysis of samples, in which the benefits due to the deacidification treatments are measured in terms of pyrolysis temperature of cellulose. These new formulations of nanoparticles dispersions expand the palette of available tools for the conservation of cellulose-based works of art, such as easel paintings, and manuscripts, potentially opening the way for the intervention on parchment and leather, whose preservation is a particularly challenging task.
Cellulose‐based artefacts are highly prone to degradation, especially in the presence of acidic compounds, which trigger the depolymerization of cellulose chains and lead to a loss in the original ...mechanical resistance of the material. Calcium hydroxide nanoparticles dispersed in organic solvent have been recently proposed for the deacidification of cellulose‐based artworks. In this work, changes induced on paper by a deacidification treatment, following an acidification bath, were studied by nuclear magnetic resonance (NMR) relaxometry and by the so‐called NMR diffraction of water trapped in the cellulose network. The deacidification treatment modifies intrachain and interchain bonds in hydrolyzed and degraded cellulose, leading to a buffered cellulose network configuration, which is similar to that characterizing the untreated reference sample in terms of relaxation parameters. Overall, calcium hydroxide nanoparticles are demonstrated effective in hindering the degradation of cellulose induced by acids and ageing in strong environmental conditions, even from the standpoint of cellulose network arrangement. It is worth noting, too, that the unilateral NMR device used for the relaxation measurements may represent a powerful tool for the preservation of cellulose‐based artworks because it allows for the monitoring of the conservation status of cellulose in a completely non‐invasive manner.
Two‐dimensional NMR relaxation and NMR diffraction are effective in tracking bond modifications in acidic/deacidified cellulose, proving an ideal noninvasive tool to assess the preservation of cellulose‐based artworks from degradation and ageing, even under strong environmental conditions, by application of calcium hydroxide nanoparticles.
The prominent degradation mechanism of cellulose is the acid-catalyzed hydrolysis of glycosidic bonds, which results in the decrease of the degree of polymerization (DP) and, macroscopically, in the ...dramatic decay of the mechanical resistance of cellulose-based materials. Alkaline nanoparticles in organic solvents have been recently proposed for the deacidification of cellulose-based artworks. Their effectiveness has been demonstrated in previous studies, by pH and DP measurements, colorimetric and thermal analyses. Herein, the changes in the cellulosic network following an acidification bath and a consequent deacidification treatment using Ca(OH)
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nanoparticles, have been investigated by NMR self-diffusion dynamics of water and related to the changes of samples’ DPs. The deacidification treatment modifies intra- and inter-chain interactions, leading to a buffered cellulose network configuration similar to that characterizing the untreated reference sample in terms of diffusive parameters and confining environment. Such results are plausibly due to a rearrangement in connectivity of the cellulosic network, even though with a different physical fingerprint with respect to the reference sample. The analysis of tortuosity of the cellulosic network in acidic and deacidified samples confirms this conclusion, further corroborating the idea that calcium hydroxide nanoparticles are an effective tool to hamper the degradation of cellulose induced by acids and aging in strong environmental conditions, even from the standpoint of cellulose network arrangement.
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