Background and aim Dental tourism, which reflects the provision of health care services abroad, also includes a travelling component. Air travel after dental intervention may cause barotrauma and ...barodontalgia. This paper aimed to provide guiding principles regarding the minimal time interval between dental procedures and air travel to prevent these adverse effects.Methods A literature search was performed to reveal information with regards to complications related to flights following dental treatments. There is little research in this area and most of it has been conducted on the military aircrew population, which has different characteristics of flight and personnel than civilian commercial flights.Results The recommended time of flying is one week after most dental intervention and six weeks after a sinus lift procedure. The minimal time required between a procedure and flight is 24 hours after restorative treatment, 24-48 hours after simple extraction, 72 hours after nonsurgical endodontic procedure, surgical extraction, and implant placement, and at least two weeks after sinus lift procedure.Conclusions The provided guidelines may serve as a starting point for the clinician's decision-making. The tailoring of an individual treatment plan to the patient should take into consideration the patient's condition, dental procedure, complications and flight characteristics. Further research based on commercial flights is needed to formulate more accurate guidelines for the civilian population.
The properties of new coatings with nanopigments (NPs) prepared by the dye mixture treatment of montmorillonite modified with cationic surfactants were investigated. The colorimetric parameters of ...polymer films with nanopigments were determined. The mutual interference of the dyes in their adsorption on nanoparticles and their colourfastness (photostability) to light was analysed. The properties of oligomer/monomer compositions with synthesised nanopigments designed for the printing of non-metallic surfaces were discussed. The structure of nanopigments and polymerised oligomer/monomer compositions was revealed by small-angle X-ray diffraction, UV–Vis spectra, and atomic force microscopy. NPs with a wide colour range were prepared using dye mixtures. One other advantage of these NPs over NPs based on individual dyes is the possibility to increase the total concentration of the colouring components in the NPs and to increase the colourfastness.
The effect of polymer film elongation leading to the thinning of the film up to three times on the decay of transients was studied. Kinetics of benzophenone (B) triplet state 3 B* and ketyl free ...radical BH• in soft rubber poly(ethylene-co-butylene) (abbreviated as E) was investigated by nanosecond laser flash photolysis. We monitored decay kinetics of the triplet state of 3 B* and of BH• decay in the polymer cage and decay of BH• in the polymer bulk. The fast exponential decay of 3 B*(lifetime τT ≈ 200 ns) is accompanied by hydrogen atom abstraction from E with the formation of BH• and a polymer free radical R•. The decay of BH• in the polymer cage occurs during τc ≈ 1 μs. Cage recombination, in turn, was followed by a cross-termination of BH• in the polymer bulk (τb ≈ 100 μs under our conditions) and is characterized by a rate constant k b ≈ 108 M–1 s–1. We studied changes of rates of transients decay upon elongation (thinning) of E. Decay of 3 B* is practically independent of elongation of the film. Recombination of BH• in the solvent bulk occurs with a two times lower k b than in a nonelongated E. The decrease in k b is ascribed mainly to a lower fractional polymer free volume V f in elongated E compared with that in nonelongated E. Dependencies of log10 k b versus l − 1 , where l is the thickness of the film, turned out to be linear with a negative slope. At the same l recombination proceeds slower in the elongated elastomer compared with the nonelongated elastomer. Cage effect increases twice as well due to a lower rate of radicals escape from the polymer cage in the elongated film. We observed relatively large effects of external magnetic field (B = 0.2T) on the kinetics of cage recombination and recombination in the polymer bulk. Magnetic field effect on recombination rates in the cage and in the solvent bulk does not depend on elongation.
The photoinduced reactions of benzophenone (B) in biaxially oriented polypropylene (BOPP) were studied with nanosecond laser photolysis (N2 laser, λ337.1 nm). The first observed transient was a ...triplet state 3 B*. Decay of 3 B* led to formation of a radical pair (RP) of BH• and R• , where R• is a radical formed by hydrogen abstraction from BOPP (RH) by 3 B*. We studied BOPP after the preheating for a short time in a temperature range 298–423 K, which is essentially lower than its melting point of 453 K. All measurements with not-heated and with preheated (annealed) BOPP were made at 298 K. A radical pair (RP) apparently decays as a contact pair 3BH• , R• in nonheated BOPP. A critical phenomenon takes place: dissociation of RP with a formation of free radicals in the polymer bulk is observed at preheating temperature T crit ≈ 403 K and at a higher T. The physical process of heating and cooling of BOPP apparently resulted in the restructuring of crystallites, their agglomeration, shrinking of the distribution of crystallites according to their sizes in BOPP. Overall BOPP becomes softer which manifests itself in the radical kinetics. The decay kinetics of 3 B* and RP in the cage fits well the first-order law. Rate constants were obtained. Radicals BH• , which exit into the polymer bulk at temperatures of preheating T ≥ 403 K, decay by cross-termination according to the second-order law. A relatively high rate constant ∼108 M–1·s–1 for this reaction was obtained due to diffusion of BH• enclosed in the soft amorphous phase of BOPP. Properties of BOPP containing B were studied with ESR, DSC, IR, and WAXD.
The decay kinetics of intermediates produced under photolysis of benzophenone (B) dissolved in soft rubber poly(ethylene-co-butylene) films (abbreviated as E) was studied by ns laser flash photolysis ...in the temperature range of 263-313 K. We monitored decay kinetics of the triplet state of (3)B* and of benzophenone ketyl free radical BH˙. The fast exponential decay of (3)B* (life-time τT ≈ 200 ns) is accompanied by hydrogen atom abstraction from E with a formation of BH˙ and a polymer free radical R˙. Decay of (3)B* was followed by decay of BH˙ in the polymer cage (geminate recombination) with τc ≈ 1 μs. Cage recombination in turn was followed by a decay of BH˙ in the polymer bulk (τb ≈ 100 μs). Fortunately, all three processes are separated in time. Both cage and bulk reactions were decelerated by the application of magnetic field (MF) of 0.2 T by approximately 20%. Geminate recombination was fit to the first-order kinetic law, and recombination in the solvent bulk fits well to the second-order law. Both geminate recombination and recombination in the solvent bulk are predominantly a reaction between BH˙ and R˙. It was assumed that the reaction radius ρ12 and a mutual diffusion coefficient D12 of BH˙ and R˙ are the same for the cage and bulk recombination, respectively. This led to an estimation of ρ12 = 3.3 nm and D12 = 1 × 10(-7) cm(2) s(-1). These values are discussed. We obtained activation energy, Eact, equal to 6 kcal mol(-1) and 7 kcal mol(-1) for cage decay and for recombination in the polymer bulk, respectively. These Eact coincide with each other within experimental error of their determination (±0.5 kcal mol(-1)). This indicates the same diffusion character in the cage and in the polymer bulk. It was demonstrated that an exponential model of cage effect sufficiently describes the obtained experimental data in rubber.
Ultraviolet‐visible (UV‐vis) absorption, flash photolysis, and 1H and 13C NMR spectroscopy were used to investigate the mechanism of formation and structure of complexes in the ...1',3',3'‐trimethylspiro2H‐1‐benzopyran‐2,2'‐indoline (SP, also well known as BIPS) with Al3+ (inorganic salts) in ethanol (EtOH), methanol (MeOH), and in aqueous MeOH solutions. A labile (equilibrium constants ≤ 5000 M−1) complex of SP and Al3+ with broad absorption band in the UV‐vis with λmax = 380 nm appeared promptly in the presence of an excess of Al3+. The slow formation of a stable complex (SC) between Al3+ and two merocyanine (MC) forms of SP with an intensive absorption band at λmax = 430 nm is observed with a yield of 1.0 upon keeping the solutions of these two compounds at constant concentration ratio Al3+ ≥SP/2 in the dark. The rate constants of such SC formation were close to the corresponding rate constant of the transformation of SP into MC in the dark (5.0×10−5‐1×10‐3 s‐1, depending upon the solvent). The photolysis of the SC with visible light (λ > 400 nm) results in the total conversion of the SC into SP. The SC forms promptly after the addition of Al3+ at concentrations of the same order as those of MC. This method allows detection of Al3+ to concentrations as low as 50 nM. The kinetics and thermodynamic parameters of the SP and MC reactions and of their complex formation with Al3+ are discussed.
A new stable colored complex of a merocyanine form of 1',3',3'‐trimethylspiro2H‐1‐benzopyran‐2,2'‐indoline with Al3+ was observed. Spectroscopic, kinetic, and thermodynamic properties of the study systems are presented. The developed method allows detection of Al3+ at concentrations as low as 50nM.
Laser Flash Photolysis of Benzophenone in Polymer Films Levin, Peter P; Khudyakov, Igor V
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
10/2011, Letnik:
115, Številka:
40
Journal Article
Recenzirano
With a nanosecond laser we studied flash photolysis of benzophenone (BP) dissolved in four different polymer films. We measured kinetics of decay of a triplet state of benzophenone 3BP as well as ...kinetics of decay of benzophenone ketyl free radicals BPH•. Polymer matrices have plenty of reactive C–H bonds, and the hydrogen abstraction by 3BP leads to a formation of geminate pair which either recombines into molecular products or dissociates. Decay kinetics of 3BP is well described by dispersive kinetics and in particular by the kinetic law suggested in Albery W. J. ; et al. J. Am. Chem. Soc. 1985, 107, 1854 . We observed a broader distribution of rate constants in hard films. It was observed that the decay kinetics of transients radicals in the “hard” polymers is quite satisfactory described by the same law for dispersive kinetics. Kinetics of radicals decay in “soft” polymers is satisfactorily described as a diffusion- enhanced reaction. Effect of a hardness of polymer matrix on the measured kinetic parameters is discussed.
Photoinduced elementary reactions of low-MW compounds in polymers is an area of active research. Cured organic polymer coatings often undergo photodegradation by free-radical paths. Besides practical ...importance, such studies teach how the polymer environment controls elementary free-radical reactions. Presented here is a review of recent literature which reports such studies by product analysis and by a time-resolve technique of photochemical reaction inside the cage of a polymer and in the bulk of a polymer. It was established that application of moderate external magnetic field allows the control of the kinetics of free radicals in elastomers. Preheating and stretching of elastomers affect reactivity of photoproduced radicals.
The luminescent properties of photocured aliphatic and aromatic network polycarbonate methacrylates, containing organic fluorescent dyad, have been studied. The dyad molecule includes two ...photosensitive fragments—tetraarylimidazole with a hydroxyl group and azomethinocoumarin—in each of which excited state intramolecular proton transfer (ESIPT) occurs, leading to the appearance of two emissions: blue (450 nm) and green (535 nm). It was established that the ratio of the intensities of these emissions depends very significantly on the excitation wavelength, as well as on the length, flexibility and polarity of the matrix oligomeric bridges.
To build a catalog of peptides presented by breast cancer cells, we undertook systematic MHC class I immunoprecipitation followed by elution of MHC class I-loaded peptides in breast cancer cells. We ...determined the sequence of 3196 MHC class I ligands representing 1921 proteins from a panel of 20 breast cancer cell lines. After removing duplicate peptides, i.e., the same peptide eluted from more than one cell line, the total number of unique peptides was 2740. Of the unique peptides eluted, more than 1750 had been previously identified, and of these, sixteen have been shown to be immunogenic. Importantly, half of these immunogenic peptides were shared between different breast cancer cell lines. MHC class I binding probability was used to plot the distribution of the eluted peptides in accordance with the binding score for each breast cancer cell line. We also determined that the tested breast cancer cells presented 89 mutation-containing peptides and peptides derived from aberrantly translated genes, 7 of which were shared between four or two different cell lines. Overall, the high throughput identification of MHC class I-loaded peptides is an effective strategy for systematic characterization of cancer peptides, and could be employed for design of multi-peptide anticancer vaccines.
By employing proteomic analyses of eluted peptides from breast cancer cells, the current study has built an initial HLA-I-typed antigen collection for breast cancer research. It was also determined that immunogenic epitopes can be identified using established cell lines and that shared immunogenic peptides can be found in different cancer types such as breast cancer and leukemia. Importantly, out of 3196 eluted peptides that included duplicate peptides in different cells 89 peptides either contained mutation in their sequence or were derived from aberrant translation suggesting that mutation-containing epitopes are on the order of 2–3% in breast cancer cells. Finally, our results suggest that interfering with MHC class I function is one of the mechanisms of how tumor cells escape immune system attack.
•We identified more than 2800 unique HLA peptides from a panel of basal, luminal, and claudin-low subtype of cell lines.•HLA binding prediction across all tested cells allowed us to propose a way used by cancer cells to avoid the immune attack.•We identified 16 previously known immunogenic peptides. Importantly, 8 of them were shared between different cell lines.•We also identified 89 neoepitopes, 7 of which were shared between different cell lines.
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