In Plane Behaviour of Masonry Walls Reinforced with Mortar Coatings and Fibre Meshes

Concerning strengthening techniques for existing masonry walls, the trend is toward the use of Fibre Reinforced Mortar (FRM) with both a significant increase of the mortar strength, and a drastic thickness reduction of the added external layers. In the present analysis, the focus is posed on some new lime mortar types which possess a very high strength in tension, although the elastic modulus remains in a normal range, leading so to a considerable toughness increase. The G-FRM system is composed with a glass fibre mesh which must possess a tensile resistance larger than the one of the mortar area including it, and this allows introducing some ductility in the composite. A total of 14 diagonal compression tests of masonry walls reinforced with G-FRM have been completed at LISG (Structural Engineering and Geotechnics Laboratory, University of Bologna), encompassing different FRM combinations. More precisely, the walls were reinforced with three different lime mortar compounds with layer thicknesses of 12, 15 and 30 mm, and reinforced with two different glass fibre meshes and two different arrangements of steel micro-wire strips. The performed tests showed that the interpretation of the observed behaviour needs a sound theoretical basis of the experimental setup, avoiding the simple analysis reported in standards and codes. A finite element model of the experimental setup was prepared, able to identify the features of the observed behaviour. Following this suggestion, a new theoretical model based on Mohr-Coulomb plasticity was defined and applied to the interpretation of a large database of experimental tests with a very good agreement

One-sample aggregate data meta-analysis of medians

An aggregate data meta-analysis is a statistical method that pools the summary statistics of several selected studies to estimate the outcome of interest. When considering a continuous outcome, typically each study must report the same measure of the outcome variable and its spread (e.g., the sample mean and its standard error). However, some studies may instead report the median along with various measures of spread. Recently, the task of incorporating medians in meta-analysis has been achieved by estimating the sample mean and its standard error from each study that reports a median in order to meta-analyze the means. In this paper, we propose two alternative approaches to meta-analyze data that instead rely on medians. We systematically compare these approaches via simulation study to each other and to methods that transform the study-specific medians and spread into sample means and their standard errors. We demonstrate that the proposed median-based approaches perform better than the transformation-based approaches, especially when applied to skewed data and data with high inter-study variance. In addition, when meta-analyzing data that consists of medians, we show that the median-based approaches perform considerably better than or comparably to the best-case scenario for a transformation approach: conducting a meta-analysis using the actual sample mean and standard error of the mean of each study. Finally, we illustrate these approaches in a meta-analysis of patient delay in tuberculosis diagnosis

Experimental characterization of mortar by testing on small specimens

The experimental characterization of mortar mechanical properties in existing masonry constructions is considerably complex. Whereas bricks parameters can be assessed with a sufficient precision, the mortar properties are very difficult to obtain and the results are highly dispersed. For instance, the in-situ techniques based on the measurement of the amount of energy required to drill a small cavity provide very scattered values that should be handled cautiously. Also, the characterization of existing mortar joints by means of surface testing may be difficult, since the surface decay or even the presence of new restoration mortar may spoil the results. On the other hand, tests on small mortar cubes or double punch tests usually lead to inaccurate estimates of mechanical characteristics, since the confining effect exercised by bricks on the mortar layer is completely disregarded. Another difficulty is the extraction of undisturbed specimens from the joints of existing brickwork. Such problems can be overcome by laboratory destructive testing on small specimens including both bricks and mortar. This activity is suitable for existing historic buildings, since it does not inflict severe damage on the structural element. This work presents the results of a comprehensive experimental program on cores including a central mortar layer along a symmetry plane. Such specimens were easily extracted by different panels of an existing historical building using a common core drill. The cores were subjected to splitting test with a particular set-up, providing 30°, 45° or 60° inclinations of the mortar layer with respect to the loading plane. This test induces a mixed compression–shear stress state in the central mortar layer. The experimental results have been interpreted using different failure criteria in order to assess the mechanical properties of mortar.Postprint (published version

Interpretation formulas for in situ characterization of mortar strength

Abstract The in situ characterization of mortar mechanical properties is a mandatory activity in every structural assessment of existing monumental buildings. Fine and complex numerical models are meaningless if the material parameters are hypothetical or based on reference values since there exist thousands of mortar compositions and brick types and aging processes do change values in a not easily predictable way. Therefore direct investigation of the mortar courses is a key ingredient, and this requires specific tools able to deal with thin layers of materials and requirements of conservation. There are however several ways able to investigate mortars without extracting consistent specimens, and most of them can be interpreted within the common framework of a Mohr-Coulomb plasticity constitutive behavior. Several of these techniques are even capable to discriminate superposed repointing layers of sufficient depth. In the paper, some versatile and effective mortar investigation techniques are reviewed and the formulas for the strength class definition are presented. Then, the predictive ability of the proposed formulas is checked against large experimental campaigns. Finally, an interesting investigation on the Ponte Taro bridge in Parma is used in comparing the results of different experimental tools. The data show a general good agreement among the mechanical properties extracted with the proposed procedures

Ion acceleration by radiation pressure in thin and thick targets

Abstract Radiation Pressure Acceleration (RPA) by circularly polarized laser pulses is emerging as a promising way to obtain efficient acceleration of ions. We briefly review theoretical work on the topic, aiming at characterizing suitable experimental scenarios. We discuss the two reference cases of RPA, namely the thick target ("Hole Boring") and the (ultra)thin target ("Light Sail") regimes. The different scaling laws of the two regimes, the related experimental challenges and their suitability for foreseen applications are discussed

Supposed trans-Atlantic migration of Heterostegina around the Eocene/Oligocene boundary

According to our hypothesis, Heterostegina ocalana migrated eastward through the previously much narrower Atlantic Ocean around the Eocene/Oligocene boundary. Sporadic populations of H. n. sp., its phylogenetic successor, survived in the western part of the Neotethys until the end of the Rupelian, when they became extinct

Corneal Deposit of Ciprofloxacin after Laser Assisted Subepithelial Keratomileusis Procedure: A Case Report

Purpose. To report one case of corneal antibiotic deposition after ciprofloxacin administration in Laser Assisted Subepithelial Keratomileusis (LASEK). Methods. One case of post-LASEK treatment resulted in corneal precipitates and poor wound healing. Debris was analyzed with dark field microscopy and placed on a blood-agar plate seeded with a susceptible stain of Staphylococcus aureus (ATCC 29213). Results. The alterations resolved with discontinuation of ciprofloxacin treatment, although some residual deposits persisted subepithelially for 6 months. Analysis of precipitates revealed polydisperse crystalline needles of 183 μm average length (SD = 54 μm) and the excised precipitate demonstrated a zone of inhibition. Conclusions. Fluoroquinolone antibiotic drops have been used extensively in postsurgical treatment of refractive surgery. Corneal precipitates have been previously reported in the literature, but up to now nothing has been documented after LASEK. Polypharmacy during refractive surgery may impair epithelialisation, and clinical management should reduce toxic environment and promote ocular surface stability when performing surface ablations

A comparison of analytic approaches for individual patient data meta-analyses with binary outcomes

Abstract Background Individual patient data meta-analyses (IPD-MA) are often performed using a one-stage approach-- a form of generalized linear mixed model (GLMM) for binary outcomes. We compare (i) one-stage to two-stage approaches (ii) the performance of two estimation procedures (Penalized Quasi-likelihood-PQL and Adaptive Gaussian Hermite Quadrature-AGHQ) for GLMMs with binary outcomes within the one-stage approach and (iii) using stratified study-effect or random study-effects. Methods We compare the different approaches via a simulation study, in terms of bias, mean-squared error (MSE), coverage and numerical convergence, of the pooled treatment effect (β 1) and between-study heterogeneity of the treatment effect (τ 1 2 ). We varied the prevalence of the outcome, sample size, number of studies and variances and correlation of the random effects. Results The two-stage and one-stage methods produced approximately unbiased β 1 estimates. PQL performed better than AGHQ for estimating τ 1 2 with respect to MSE, but performed comparably with AGHQ in estimating the bias of β 1 and of τ 1 2 . The random study-effects model outperformed the stratified study-effects model in small size MA. Conclusion The one-stage approach is recommended over the two-stage method for small size MA. There was no meaningful difference between the PQL and AGHQ procedures. Though the random-intercept and stratified-intercept approaches can suffer from their underlining assumptions, fitting GLMM with a random-intercept are less prone to misfit and has good convergence rate