Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD4OL (Spearman's rank correlation coefficient [r(s)], -0.33; P < 0.001), sNox2-dp (r(s), -0.57; P < 0.0001), and urinary excretion of isoprostanes (r(s), -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2 alpha-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation

Effect of Pressure on the Shear Properties of Elastomeric Compounds

High Damping Rubber (HDR) is used in the manufacturing of elastomeric bearing for seismic isolation of building and structures. In service rubber bearings are subjected to a permanent vertical load which may change at the occurrence of the earthquake, and potential shear deformation induced by the seismic ground motion. This study investigates the response of five commercial elastomeric compounds used in the manufacture of HDRB with shear modulus between 0.4MPa and 1.4 MPa, and equivalent viscous damping between 0.06 and 0.16 under combined compression and shear, with compressive stresses ranging from 0 up to 18 MPa. Soft rubbers seem to be more sensitive to the compression load than hard rubbers as far as the damping factor is concerned, whereas the influence of the compression load on the shear modulus seems to be peculiar of every mixture and not apparently related on the hardness, which can explain the inconsistencies found in literature relevant to the studies on full scale rubber bearings

Experimental Assessment of High Damping Rubber Under Combined Compression and Shear

High damping rubber (HDR) is used in the manufacturing of elastomeric bearings for seismic isolation of building and structures. In practical situations, rubber bearings are subjected to a permanent vertical load which may change at the occurrence of the earthquake, and concurrent shear deformation, due to either service movements of the structure or earthquake-induced ground motion. The study presents an experimental procedure for the assessment of HDR specimens under combined compression and shear, reproducing the same typical load regimes which rubber isolators experience in service. Five commercial HDRs were tested according to the procedure. The results point to the importance of considering the influence of the compression stress for a correct understanding of the behavior of HDRs under cyclic shea

DYNAMIC RESPONSES OF RUBBER COMPOUNDS FOR ANTI-SEISMIC ISOLATORS

The mechanical properties of the elastomers used in the manufacture of seismic rubber isolators are sensitive to mechanical and environmental working conditions, therefore resulting in large variation ranges of the performance of seismic isolation systems installed in buildings and structures. The study investigates the cyclic stress–strain behavior of several elastomer compounds used in the manufacture of anti-seismic rubber bearings. The influence of mechanical and environmental factors, including strain amplitude, number of cycles, frequency, air temperature, and application of concurrent compressive and shear stresses, on the shear properties of the compounds is assessed. The results are analyzed and used to calculate modification factors of design properties for each compound. The variability of the mechanical properties is studied and compared to the requirements on production rubber bearings set in the current European standard on anti-seismic device

RE-CENTRING CAPABILITY OF FRICTION PENDULUM SYSTEM: EXPERIMENTAL INVESTIGATION

In this paper the re-centring capability of the Friction Pendulum System (FPS) is investigated in shake table tests carried out on a steel frame mock up. FPS prototypes with different coefficient of friction are studied. The response of the isolation system is analysed in terms of residual displacements after the end of the earthquake and accumulation of irreversible displacements during a sequence of successive ground motions. The features of the FPS that ensure sufficient re-centring capability are identifie

Experimental Assessment of the Re-Centring Capability of Curved Sliding Bearings in Shake Table Tests

The re-centring capability of isolation systems with curved sliding bearings is investigated in shake table tests carried out on a 1-story steel frame with rectangular plan, scaled at one third-length scale and isolated with four bearings. The coefficient of friction of the bearings is varied by changing the material or lubrication condition of the pads, and the response is assessed under different sequences of ground motion waveforms in terms of residual displacement after the ground motion and accrual of displacements after a series of identical earthquakes. Current code re-centering provisions are finally checked against the experimental data

RE-CENTRING CAPABILITY OF FRICTION PENDULUM SYSTEM: PARAMETRIC INVESTIGATION

Self-centring capability after the seismic shaking is one of the fundamental functions required to seismic isolation systems. Low re-centering capacity may lead to serious damage and even structural collapse due to excessive cumulative displacements. Near fault quakes, frequently characterized by large pulse, may have a strong impact on the behavior of the isolation systems leading in some cases, to instability phenomena. In this paper are reported some preliminary results relevant to an extensive parametric study aimed to investigate the re-centering capability of Friction Pendulum System (FPS) isolators and its sensitivity to pulse-like ground motions. A wide range of devices and ground motions, characterized by different values of the isolator characteristic parameters (equivalent radius Req and coefficient of friction eq) and of the pulse-like characteristics of the seismic ground motion has been considered. The latters have been calculated in terms of the “predominant period” of the ground motion and through the introduction of a “kinetic Pulse Index” defined in terms of the rate of transmission of the kinetic energy. The preliminary results, discussed herein in terms of maximum and residual displacements of the isolators, show that both the mechanical properties of the isolator (restoring stiffness and frictional damping) and the characteristics of the ground motion, but also their relationships, may have an important influence on the recentering capability of the device

Lateral shear cyclic testing of full-scale precast bearing wall panels with inner lightening profiles and mechanical connections / prove cicliche a taglio laterale di elementi di muro prefabbricati con profili di alleggerimento e connessioni meccaniche

Un innovativo elemento di muro portante prefabbricato con elementi di alleggerimento interni e connessioni meccaniche \ue8 stato recentemente proposto come un\u2019evoluzione dei sistemi tradizionali a grandi pannelli impiegati per la costruzione di edifici resi-denziali. Il comportamento flessionale del muro proposto \ue8 stato oggetto di precedenti attivit\ue0 di ricerca che hanno incluso prove sismiche su un edificio multipiano in scala al vero. L\u2019articolo presenta i risultati di prove di taglio laterale cicliche svolte presso il laboratorio LPMSC del Politecnico di Milano su quattro elementi di muro rivolte alla caratterizzazione del comportamento meccanico del muro a taglio con l\u2019impiego di differenti schemi di disposizione di armatura di parete. Sono stati identificati diver-si modi di rottura a taglio, da taglio-trazione diagonale in muri debolmente armati a taglio-scorrimento orizzontale in muri mag-giormente armati. Un modello puntoni e tiranti \ue8 stato inoltre impiegato per fornire un\u2019interpretazione ingegneristica ai risultati sperimentali.An innovative precast shear wall with inner lightening profiles and mechanical connections has been recently proposed as an evo-lution of the standard large panel technology for residential precast systems. The structural behaviour of the proposed wall system under flexure has been previously assessed, including seismic testing of a full-scale multi-storey building. This paper presents the results of lateral shear tests carried out at the LPMSC laboratory of Politecnico di Milano on four precast bearing wall panel ele-ments of this system, aimed at characterising its structural behaviour under shear and the influence of different shear reinforce-ment layouts. Different shear failure modes have been identified, from diagonal tension-shear in weakly-reinforced walls to hori-zontal sliding-shear in heavily-reinforced walls. A strut and tie model was also set up to give the experimental results an enginee-ring interpretation

Vitamin E-coated filter decreases levels of free 4-hydroxyl-2-nonenal during haemodialysis sessions

Uraemic subjects undergoing chronic haemodialysis show increased oxidative stress. The use of non-biocompatible filters and reduced antioxidative defences are important sources of reactive oxygen species (ROS) release. The highly oxidative environment accelerates the onset and progression of tissue damage and atherosclerotic cardiovascular disease. The aldehyde 4-hydroxyl-2-nonenal (HNE) is probably the best marker of oxidative stress. In this study, the concentration of plasma HNE was evaluated in eight uremic subjects during two sessions of haemodialysis: the first using a standard biocompatible filter and the second using a filter coated with vitamin E. Baseline plasma levels of HNE were elevated, and dropped during haemodialysis. At the end of the session, however, low levels were maintained only when the vitamin E-modified filter was used. By contrast, a marked increase in HNE was recorded at the end of the session in all subjects who underwent haemodialysis with the conventional filter. This study provides evidence that the vitamin E-coated filter plays a role in counteracting oxidative stress. The chronic use of vitamin E-modified filters in haemodialysed subjects might help to counterbalance oxidative attack and, consequently, contribute to preventing cardiovascular disease