Historical constructions are exposed to weathering conditions and atmospheric pollution for many years which demolish the historical material as well as dramatically influence their visual aspects. Nowadays, the development of conservative coatings with weather-resistant, self-cleaning, and hydrophobic properties is a promising challenge for carbonate stones. In this study, a simple synthesis route is developed to obtain organic-inorganic hybrid nanocomposites. The main components of the acrylate coatings are methyl methacrylate, 3-(trimethoxysilyl)propyl methacrylate (TMSM). Tetraethyl orthosilicate (TEOS) is added to the coating to improve the thermal resistance of the coating. Perfluorooctyl-trichlorosilane (FOTCS) is added to the coating to improve the weathering resistance and hydrophobic behaviour of the coating. Also, titanium dioxide (TiO 2 ) is added to improve the thermal resistance and photocatalytic feature of the coating. The results confirmed significant enhancement in contact angle and weathering resistance that originates from adding an organofluorine component in the structure of the coating. A hybrid coating includes acrylate monomers as the binder and chemical substances include an organosilane (TEOS), fluorinated silane (FOTCS) and titania nanoparticles (TiO 2 ) has appropriate properties like thermal resistance, mechanical resistance, weathering resistance, hydrophobicity, and selfcleaning that can be used as a protective coating for the precious stone-made cultural heritages.

BackgroundThis randomized study was aimed to compare the diagnostic value of two head-up tilt testing protocols using sublingual nitroglycerin for provocation in patients with recurrent unexplained syncope and normal heart.MethodsThe patients with normal findings in physical examination, electrocardiography and echocardiography were randomly submitted to one of upright tilt test protocols. The only difference between two protocols was that nitroglycerin was administered after a five minute resting phase in supine position during protocol B. We also considered eighty normal persons as the control group.ResultsOut of 290 patients that underwent tilt testing, 132 patients were in group A versus 158 patients in group B. Both groups had an identical distribution of clinical characteristics. Tilt test was positive in 79 patients in group A (25 in passive phase, 54 in active phase) versus 96 patients in group B (43 in passive phase, 53 in active phase). There was no significant difference between results in two groups (P value= 0.127). Forty cases were tested with protocol A and forty underwent tilt testing with protocol B. Tilt test was positive in 4 cases with protocol A versus 3 cases in protocol B. The positive rates of tilt testing with protocol A was 60% while it was 61% in protocol B. The specificity of testing with protocol A was 90% and it was 92.5% in protocol B.ConclusionsAccording to our data, adding a period of rest and returning to supine position before nitroglycerin administration had no additional diagnostic yield.