Sorption thermodynamics of organic pollutants onto zeolitic tuff: Isosteric and standard enthalpy

The isotherms of sorption of six organic pollutants (benzyl alcohol, phenol, cyclohexanol, o-xylene, toluene and cyclohexane) from water solutions onto a zeolitic tuff (Si/Al ratio = 2.4) have been determined by batch experiments at 4; 14; 24 and 34C. Sorbitivity (amount of solute sorbed per unit dry mass sorbent at the equilibrium) was very low for all molecules tested, particularly so for the hydroxyl compounds. Comparison of Freundlich parameters and the values of isosteric and standard enthalpy as determined in the present study with analogous data for immobilized humic acid and humic acid-zeolite adducts confirms that the sorbing properties of the adducts are not the sum of its components.     

Biexponential and diffusional kurtosis imaging, and generalised diffusion-tensor imaging (GDTI) with rank-4 tensors: a study in a group of healthy subjects

Object Clinical diffusion imaging is based on two assumptions of limited validity: that the radial projections of the diffusion propagator are Gaussian, and that a single directional diffusivity maximum exists in each voxel. The former can be removed using the biexponential and diffusional kurtosis models, the latter using generalised diffusion-tensor imaging. This study provides normative data for these three models. Materials and methods Eighteen healthy subjects were imaged. Maps of the biexponential parameters D _fast, D _slow and f _slow, of D and K from the diffusional kurtosis model, and of diffusivity D′ were obtained. Maps of generalised anisotropy (GA) and scaled entropy(SE) were also generated, for second and fourth rank tensors. Normative values were obtained for 26 regions. Results In grey versus white matter, D _slow and D′ were higher and D _fast, f _slow and K were lower. With respect to maps of D′, anatomical contrast was stronger in maps of D _slow and K. Elevating tensor rank increased SE, generally more significantly than GA, in: anterior limb of internal capsule, corpus callosum, deep frontal and subcortical white matter, along superior longitudinal fasciculus and cingulum. Conclusion The values reported herein can be used for reference in future studies and in clinical settings.     

FRP Confinement of Tuff and Clay Brick Columns: Experimental Study and Assessment of Analytical Models

In recent years, fiber-reinforced polymer (FRP) wrapping effectiveness has been clearly confirmed especially with reference to concrete structures. Despite evident advantages of FRP based confinement on members subjected to compressive overloads due to static or seismic actions, the use of such technique in the field of masonry has not been fully explored. Thus, to assess the potential of confinement of masonry columns, the present paper shows the results of an experimental program dealing with 18 square cross sections (listed faced tuff or clay brick) masonry scaled columns subjected to uniaxial compression load. In particular, three different confinement solutions have been experimentally analyzed in order to evaluate and compare the effectiveness of uniaxial glass FRP, carbon FRP, and basalt FRP laminates wrapping. The main experimental outcomes are presented and discussed in the paper considering mechanical behavior of specimens, axial stress-axial strain relationships, and effective strains at failure on the reinforcement. Test results have showed that the investigated confining systems are able to provide significant gains both in terms of compressive strength and ductility of masonry columns. Results of the presented experimental activity along with data available in the literature have been finally used to assess the reliability of the main existing analytical models; refined equations have been then proposed to minimize the scattering between theoretical predictions and experimental available data.     

FRP Strengthening of Full-Scale PC Girders

Every year, several prestressed concrete (PC) bridge girders are accidentally damaged by overheight vehicles or construction equipment impact. Although complete replacement is sometimes deemed necessary, repair and rehabilitation can be far more economical, especially when the time and the installation cost of the repair system are drastically reduced. The use of fiber-reinforced polymer (FRP) composites to restore the original capacity of impacted PC girders are being increasingly considered for bridge applications due to their high strength-to-weight ratios, corrosion and fatigue resistance, their ease of transport and handling and their potential for tailorability. Experimental data on full-scale PC girders strengthened by using FRP laminates are very limited; the present paper is intended as an extension of a previous experimental work conducted by writers [as reported by M. Di Ludovico et al. ACI Struct. J. 102(5), 97–109 (2005)] on three full-scale PC specimens. In particular, tests on five full-scale (1,300 mm long, 1,050 mm high) PC I-shaped girders with RC slabs, designed according to ANAS (Italian Transportation Institute) standard specifications, are presented. One beam was used as control and the other four were intentionally damaged in order to simulate a vehicle impact by removing the concrete cover and by cutting a different percentage of tendons (17% on two specimens and 33% on the remaining two). The repair, by using externally bonded carbon FRP (CFRP) laminates installed by wet manual layup, was aimed at restoring the ultimate flexural capacity of the member, taking particular attention to the laminate’s anchoring system. Main experimental phases along with the comparison of tests results in terms of flexural capacity, deflections, strains, and failure modes are herein presented and discussed with reference to control, damaged, and CFRP strengthened specimens. The effectiveness of the adopted anchorage systems is also evaluated.     

Nanowires and Nanostructures that Grow like Polymer Molecules

Unique properties (e.g., rubber elasticity, viscoelasticity, folding, reptation) determine the utility of polymer molecules and derive from their morphology (i.e., one‐dimensional connectivity and large aspect ratios) and flexibility. Crystals do not display similar properties because they have smaller aspect ratios, they are rigid, and they are often too large and heavy to be colloidally stable. We argue, with the support of recent experimental studies, that these limitations are not fundamental and that they might be overcome by growth processes that mimic polymerization. Furthermore, we (i) discuss the similarities between crystallization and polymerization, (ii) critically review the existing experimental evidence of polymer‐like growth kinetic and behavior in crystals and nanostructures, and (iii) propose heuristic guidelines for the synthesis of “polymer‐like” crystals and assemblies. Understanding these anisotropic materials at the boundary between molecules and solids will determine whether we can confer the unique properties of polymer molecules to crystals, expanding them with topology, dynamics, and information and not just tuning them with size.     

THERMAL STRESSES IN MICROSTRETCH ELASTIC CYLINDERS

The present paper is concerned with the problem of thermal stresses in isotropic microstretch elastic cylinders. The temperature distribution is assumed to be a general polynomial in the axial coordinate. As in classical theory, the problem is reduced to solving the plane strain problem.     

Reference architectures modelling and compliance checking

Software and Systems Modeling - Reference architectures (RAs) are successfully used to represent families of concrete software architectures in several domains such as automotive, banking, and the...     

Minimally invasive mammary artery Doppler flow velocity evaluation in minimally invasive coronary operations

BACKGROUND: Left internal mammary artery Doppler flow velocity assessment during the Azoulay maneuver (patient's legs are passively lifted up and actively maintained by the patient) can increase the information on the anastomosis quality after left internal mammary artery to left anterior descending coronary artery grafting after the left anterior, small thoracotomy operation. METHODS: One hundred patients had an early postoperative angiography and a Doppler flow velocity assessment at rest and during the Azoulay maneuver. Peak and mean systolic velocities, peak and mean diastolic velocities, and peak and mean diastolic to systolic velocity ratios were recorded in all patients. RESULTS: In 95 patients with no restrictive conduit or anastomosis, peak and mean diastolic to systolic velocity ratios increased during the Azoulay maneuver; all but 1 patient showed at least one ratio equal to or greater than 1. In 4 patients with restrictive conduit or anastomosis, peak and mean diastolic to systolic velocity ratios were always less than 1 during the Azoulay maneuver. In the patient with an occluded conduit these ratios were less than 0.6. CONCLUSIONS: Peak and mean diastolic to systolic velocity ratios less than 1 during the Azoulay maneuver are suggestive of conduit or anastomosis malfunction. If we limit the angiographic controls to these patients, it is very likely that a pathologic anastomosis or conduit will not be missed.     

Statistical analysis of the stereolithographic process to improve the accuracy

Stereolithography (SL) is a widely used technology in the field of rapid prototyping. However, the dimensional accuracy of SL products is today still limited; therefore, this technology needs to be optimized for high precision applications. This paper presents a statistical analysis of the stereolithographic process, in order to find out the combination of parameters leading to the best accuracy of the manufactured parts. A particular benchmark was designed and a global error index was introduced to evaluate the global distortion of built parts. The Taguchi methodology was employed for the optimization. A Viper Si₂ machine by 3D Systems was used in both the modalities allowed from this system: Normal and High Resolution.Moreover, a detailed analysis of the resin polymerization mechanism was performed; from this study it emerged that the post-curing process is not always necessary if the process parameters are chosen for not having uncured areas.