This paper studied in situ, by Micro-Raman spectroscopy, the very early hydration of C 3 A in the presence and absence of sulphates and with sucrose as anadditive. For C 3 A hydration in the absence of gypsum,whencarbonation is not avoided,carbonate-AFm phases are formed, but in the presence of gypsum, hydroxi-AFmare the main phases. Ettringite is the AFm stable phase developed initially at70 minutes of hydration with gypsum and no monosulphate is formed. In the presence of sucrose, this salt, instead of sulphate,is adsorbed over the surface of the C 3 A, avoiding its reaction with sulphates until sucrose desorption. Three hours are necessary to leadto ettringite formation. A nucleation poisoning/adsorption surface mechanism is proposed for added sucrose systems. Keywords: Hydration; Micro-Raman; Admixture; Ca 3 Al 2 O 6 ; sucrose; ESEM/EDS. 1INTRODUCTIONThe characterization of the very early hydration of cement is difficult, since fresh cement pastes are highly reactive andmost materials characterization techniques (i.e. XRD, SEM, etc.)present some difficulties with the analysis of humid samples;moreover, the early developed phases must be altered when removing the free water. Drying of the cement samples, removes free water but also candegradeettringite,monosulphateand carboaluminatephases.In addition, solvent exchangemethods produce replacement of free water by an organic solvent that also can be absorbed into the surface of the phases [1][2][3][4].Thus, alternative procedures should be proposed in order to avoid any change in the sample composition. In this context, Micro-Raman spectroscopy is a very useful technique since no sample preparation is needed and insituexperiments can be performed without sample transformation.Tri-calcium aluminate (3CaO•Al 2 O 3 , C 3 A) is the most reactive phase of Portland cement (PC)that reacts with water, producing a rapid setting due toformation of metastable hexagonal hydrates (C 4 AH 13 and C 2 AH 8 ), thatevolves towards a stable phase, cubic hydrogarnet[5], C 3 AH 6 .A settingregulator, usually gypsum, is added to cement in order to control the rapid setting,the C 3 A reaction with calcium sulphate leading to ettringite(Ca 6 Al 2 (SO 4 ) 3 (OH) 12 •26H 2 O) formation. The mechanism controlling the first stage of the C 3 A-gypsum reaction is the adsorption of calcium and sulphate ions on active dissolution sites of C 3 A. That slows down the rate gradually due to the reduction of the surface area of C 3 A as the particles dissolve [6][7][8][9].Admixtures can be added to cement in order to modify normal properties; in particular retarders inhibit the setting and hardening of concrete.Sucrose,one of the most commonly used retarders, is an effective hydration inhibitor because it selectively adsorbs at C 3 A surfaces, with its ring structure intact, resulting in higher local surface coverage [10].
PurposeAccommodating intraocular lenses (A-IOLs) require capturing the ciliary muscle forces. Prior work demonstrated strong photo-initiated bonding between strips of capsular bag and poly(2-hydroxyethyl methacrylate); (pHEMA) polymer in an extraocular setting. We demonstrate that photobonding can be achieved intraocularly.MethodsPhacoemulsification was performed in porcine eyes (<24 hours postmortem). A commercial intraocular lens (IOL; pHEMA-MMA material) was inserted in the capsular bag. Surface contact between the lens and capsular bag was ensured by continuous air infusion into the anterior chamber of the eye, which provided sufficient pressure at the interface, as well as oxygen. The capsular bag and IOL then were stained with 0.1% photosensitizer Rose Bengal (RB) solution. A fiberoptic probe connected to a diode-laser (532 nm) was used to locally irradiate the capsular bag–IOL interface intraocularly. The bonding breaking load was evaluated in a uniaxial stretcher.ResultsPhotobonding occurred in the 0.8 to 1.6 W/cm2 irradiance range and 2.5 to 7 minutes irradiation time. Average forces of 0.12 N stretched but did not break the bond. These forces, applied uniaxially, are higher than the summed net accommodating force of the ciliary muscle along the entire equator (0.08 N). In two cases, the zonulae broke before the bonded region.ConclusionsPhotobonding between the capsular bag and IOL polymer can be achieved intraocularly, in a procedure compatible with standard cataract surgery. This technique will enable the mechanisms of A-IOLs not to rely on capsular bag integrity or natural haptic fibrosis.Translational RelevanceIntraocular photobonding holds promise to enable operation of A-IOLs to restore accommodation in presbyopia, affecting 100% of the population >45 years old. Intraocular bonding of polymer material to ocular tissue also may find other applications in ophthalmology.
The red fluorescence of chlorophyll is demonstrated by means of a laboratory photograph. Under ultraviolet light the chlorophyll dissolved in ethanol is fluorescent in the red range.
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