Impact of the Paper Degradation State and Constituents on Its Behavior During and After X-ray Exposure

Paper is a complex biopolymer material which contains papermaking additives and often bears inks and other graphic media. Cultural heritage paper-based artefacts are most often deteriorated to some extent. This research explores how intrinsic factors such as constituents and degradation state can impact the modifications incurred in aged papers during and after X-ray examination. To this end laboratory model papers, artificially aged, and 18th and 19th century archival documents, with and without additives (gelatin, calcium carbonate) and iron gallate ink, were exposed to Synchrotron X-ray radiation at doses that were previously shown to incur damage in unaged cotton papers (0.7 to 4 kGy). Glycosidic scissions, hydroxyl free radicals, UV luminescence and yellowing were measured immediately after the irradiation, and were monitored over a period of three years. The depolymerization of cellulose was lower in the aged papers, as well as in the papers containing calcium carbonate and gelatin, than in the unaged fully cellulosic papers. Compared to the papers with no additives, there were more hydroxyl free radicals in the papers with calcium carbonate and slightly less in the gelatin sized papers. UV luminescence and yellowing both appeared post-irradiation, with a delay of several weeks to months, while the intensity of the responses was impacted by the various paper constituents. The papers with iron gallate ink showed limited degradation in the low doses range, most probably due to recombination of the free radicals produced. Doses below 4 kGy did not cause yellowing or UV luminescence of the archival papers within the whole monitoring period. At higher doses (26 to 36 kGy), a slight UV luminescence appeared after 21 months, as well as a slight yellowing after three years, in some of them. No clear correlation between the degradation induced by the irradiation and the constituents in the paper nor its conservation state could be made. The archival papers in good conservation state depolymerized to the same extent as the model papers, while the most degraded archival papers were less impacted than the latter.

Synthesis and properties of nanostructures based on lanthanum fluoride for photodynamic therapy of tumors of the cranial cavity and bone tissue

The aim of the work is the synthesis of nanostructures based on lanthanum fluoride, promising for use in photodynamic therapy of tumors in organs of cranial cavity and bone tissues; a study of their structural properties and luminescence spectra. Synthesis of LaF3:Tb3+ was carried out by coprecipitation of components from aqueous and alcoholic (methanol) solution. As precursors were used: La(NO3)3×6H2O, TbCl3, NH4F. All reagents have qualification “chemically pure”. Distilled water and methanol were used as solvent. The synthesis of nanosized magnetite in the single-domain state was performed by the Elmore method. Synthesized nanodisperse samples are characterized by XRD analysis, DTGA, TEM. The magnetic properties and spectra of UV luminescence were also studied. It has been found that the XRD-patterns of LaF3:Tb3+ samples synthesized in water and methanol do not differ fundamentally. Under the experimental conditions, the most perfect crystals of hexagonal syngony were formed during crystallization in an autoclave. Their average size was ~ 15 nm. In TEM images, the length of the crystals exceeds the width by 3–4 times. Crystals are prone to aggregation and the formation of chain structures. The UV luminescence spectrum of the synthesized nanodisperse samples in aqueous medium at the concentration of 0.5 mg/ml and excited by ultraviolet radiation is characteristic of the structure of LaF3:Tb3+. Ensembles of particles Fe3O4/LaF3:Tb3+ NCs were synthesized. Transmission electron microscopy has shown that the shapes of particles of NCs and LaF3:Tb3+ nanocrystals are fundamentally different. Particles of Fe3O4/LaF3:Tb3+ NCs have a spherical shape, which is characteristic of structures of the core-shell type. X-ray diffraction patterns of NCs confirm this conclusion. The conditions for the synthesis of NCs did not significantly change the magnetic properties of their nuclei, single-domain Fe3O4 nanoparticles (NPs). The luminescence spectrum of Fe3O4/LaF3:Tb3+ NCs differs significantly from the spectrum of samples of nanodispersed LaF3:Tb3+ both in intensity and in the structure of the bands. These spectral differences may be due to differences in structure, features of the nanocrystalline structure, the content of the LaF3:Tb3+ scintillator and Tb3+ ions in samples of LaF3:Tb3+ nanocrystals and shells of Fe3O4/LaF3:Tb3+ nanocomposites. Composites of dispersed 60S bioglass with nanodispersed crystalline LaF3:Tb3+ in the dry state, and distilled water, showed the presence of luminescence upon excitation by UV radiation. The results of research show the prospects of the synthesized nanodispersed luminophors LaF3:Tb3+, for use as a source of luminescent radiation in optopharmacology and photodynamic therapy of tumors in organs of cranial cavity and bone tissues. Optimization of luminescent properties of the original nanodispersed luminophors, their compositions with bioactive glass, luminescent shells in the composition of magnetosensitive NCs, as well as the technology of manufacturing of these structures will significantly allow us to improve their performance characteristics. The results of the work indicate the prospects of the synthesized structures for further research under the conditions of excitation by high-permeability “soft” X-ray radiation for use in optopharmacology and photodynamic therapy of tumors in organs of cranial cavity and bone tissues. Optimization of properties of the original nanodispersed luminophors, their compositions with bioactive glass and magnetosensitive carriers Fe3O4 will allow us to improve significantly their performance characteristics.

Design and Process Optimization of a New Reaction Cavity for High-Temperature MOCVD AlGaN Growth

AlGaN offers new opportunities for the development of the solid-state ultraviolet (UV) luminescence, detectors and high-power electronic devices, however, problems such as low growth rate and poor crystallization quality are common in the growing process of AlGaN material. In this paper, a new reaction cavity for high-temperature MOCVD AlGaN growth was carried out through the research of resistance heated, and the thermal field of high-temperature MOCVD growth was numerically simulated. Based on the high-temperature MOCVD reaction cavity, an orthogonal experimental method was used to simulate the process parameters, and the range, variance and matrix analysis were conducted on the calculation results. The finite element analysis was conducted on the temperature field, pressure field, velocity field, and the high-temperature MOCVD AlGaN growth model was established.