Antonino Recupero

Cardiovascular autonomic control in myotonic dystrophy type 1: a correlative study with clinical and genetic data

The autonomic nervous system has been evaluated in myotonic dystrophy with contradictory results and its relationship with heart disturbances remains unclear. Twenty-three patients with myotonic dystrophy type 1 were investigated by a battery of six cardiovascular autonomic tests and power spectral analysis of heart rate variability. Although 15 patients (65%) revealed abnormal or borderline results in some tests, only one patient had a definite autonomic damage, as indicated by two or more abnormal tests. As a group, myotonic dystrophy type 1 patients showed a significant reduction of heart rate variability during deep breathing (P < 0.0001). The exclusive involvement of parasympathetic tests suggests that a mild vagal dysfunction occurs in some myotonic dystrophy type 1 patients. The results indicate that such autonomic abnormalities are not: (1) part of a peripheral neuropathy; (2) related to cytosine-thymine-guanine repeat size or breathing pattern. Power spectral analysis showed a reduction of supine low-frequency band, which is, but not exclusively, a marker of sympathetic activity. It was inversely correlated to disease duration (P < 0.04), suggesting a progression as the disease advances. A low-frequency power, recorded after standing, was significantly associated (P < 0.02) with presence of heart involvement. Our findings suggest that a mixed, especially parasympathetic, autonomic dysfunction may occur in myotonic dystrophy type 1, although it is not a major finding. It could play a role in the occurrence of cardiac abnormalities, or increase the risk of sudden cardiovascular events.

Simple Plastic Model for Shear Critical SFRC Beams

A simple physical model, for prediction of ultimate shear strength of steel fiber-reinforced concrete (SFRC) beams is developed on the basis of a plastic approach originally proposed for reinforced concrete beams without stirrups. It is founded on the hypothesis that cracks can be transformed into yield lines, and thus is know as crack sliding model (CSM). First, the CSM is improved to take into account the shear strength increase for deep beams, due to the arch effect. Then, the effectiveness factors for fibrous concrete under biaxial stresses are evaluated, taking into account the postcracking tensile strength of SFRC and its ability to control slippage along shear cracks. With the aim of providing a handy and fast tool for design of SFRC beams without stirrups, a simplified design model is also derived. Finally, the proposed models are validated by the results of a large set of experimental tests taken from literature.

N-M-V INTERACTION DOMAINS FOR BOX AND I-SHAPED REINFORCED CONCRETE MEMBERS

This research proposes an approximate physical model to evaluate the N-M-V interaction resistance domains for box- and I-shaped concrete cross sections. The model subdivides the concrete beam in layers, with nearly constant stress fields, and determines the internal forces satisfying equilibrium of the cross section, applying the static theorem of plasticity. The resisting contribution of the web longitudinal reinforcement is also considered by including stress fields of variable inclination on the longitudinal element direction. The proposed model leads to a conservative evaluation of bearing capacity and allows for the numerical acquisition of the N-M-V interaction resistance domains of the indicated cross sections. The obtained N-M-V failure surfaces are in good agreement with experimental test evidence performed by other researchers.

Experimental test results vs. analytical prediction of welded joint strength in hybrid steel trussed concrete beams (HSTCBs)

The aim of the paper is to provide practical guidelines for the design of welded joints of steel truss for encased composite steel–concrete beams. The results of experimental tests are presented and interpreted. The steel truss is made of a steel plate acting as the bottom chord, made of S355 structural steel, coupled with steel rebars which form the upper chord, and steel inclined web rebars (V-reverse) welded to the two chord elements, both of them made of steel B450C. Butt welded joints of web bar to bottom steel plate and fillet welding joints of inclined web bars to top chord bars were tested, as they are different from the ones which are normally used due to the coupling of different steel types and complex geometry. For the prediction of strength of fillet welding joints, two analytical expressions are derived: the first is based on a local failure criterion and the second on a limit domain of the welding section. Comparison with experimental data proves the equivalence and reliability of the proposed indications. Guidelines for choosing the effective dimensions of the fillet weld able to ensure a required strength are provided. For validation of the suggested guidelines, a high precision digital scanner is used to determine the geometrical characteristics of the fillet weld.

Evidence of cardiovascular autonomic impairment in mitochondrial disorders

ObjectiveTo investigate autonomic nervous system (ANS) function in mitochondrial disorders (MD).BackgroundMD are characterized by a wide range of clinical features, including heart abnormalities and peripheral and central nervous systems involvement. Rarely autonomic symptoms have been reported.Methods22 patients with MD underwent a battery of cardiovascular reflex tests including five tests of parasympathetic function and four tests of sympathetic function. Power spectral analyses (PSA) of heart rate variability in the supine and upright positions were also evaluated. Plasma levels of adrenaline, noradrenaline and dopamine were determined in the standing and lying positions.ResultsOnly 4/22 patients referred symptoms related to ANS dysfunction. 46% of patients had a definite autonomic damage (i. e. an autonomic score ≥ 4). 36% showed moderate alterations with an autonomic score in the range 2–3 and 18 % had a normal autonomic function. MD patients had a significantly (p <0.03) lower increase of adrenaline level after standing.ConclusionsOur data indicate an autonomic dysfunction in more than 80% of MD patients, even in the absence of a clinically manifested autonomic involvement. Cardiovascular autonomic investigation might be systematically employed in the characterization of MD.

Partial Elastic Scheme Method in Cantilever Construction of Concrete Arch Bridges

AbstractIn this paper, a study about stay stressing procedures of concrete arch bridges built by cantilevering with temporary stays is presented. Particularly, the partial elastic scheme method is proposed to find the initial cable forces, and a forward procedure is implemented to follow the actual sequence of construction by extending a procedure already applied to concrete cable–stayed bridges. The theoretical treatment is followed by a numerical application on a case study of a concrete arch bridge, and a comparison between initial cable forces found by the partial elastic scheme method and classical backward analysis is presented here. Results show the effectiveness of the proposed procedure to achieve the requested design geometry of the arch and for limiting the variation of bending moments and stay forces in construction stages.

The influence of time-dependent phenomena in segmental construction of concrete cable-stayed bridges

Construction stages of a cable-stayed bridge are characterized by a sequence in which geometric configuration, restraints and consequently stress and strain patterns vary many times till the final arrangement is achieved. When construction of concrete bridges is made by cantilever method the influence of time-dependent phenomena becomes significant. In this study an evaluation of stay stressing procedures is given by taking into account creep and shrinkage in cantilever construction of concrete cable-stayed bridges. A methodology of stay stressing is proposed with the final target of reaching the desired geometric configuration. Comparison with classical analyses performed by backward methodology is reported. A case-study is presented and discussed by performing analyses with different international creep models. Practical suggestions are given to designers, in order to minimize time-dependent effects on deck and stay internal forces and to reach an optimal final configuration.

Construction stages of cable-stayed bridges with composite deck

A cable-stayed bridge is built by following a construction sequence of different subsequent stages that imply changes of the geometric configuration, restraints and consequently stress and strain patterns. A study is presented about stay stressing sequences in cable-stayed bridges with composite deck for the case of construction made by the cantilever method. Initial cable forces are found through partial elastic schemes of construction stages. Different stay stressing procedures are implemented and a comparison between them is proposed in order to evaluate the differences in terms of deformed shape and internal force distribution of the deck and the pylon. Results can be useful to give practical suggestions to designers, when they have to deal with stay stressing sequences of composite cable-stayed bridges.

Echocardiographic assessment of subclinical left ventricular eccentric hypertrophy in adult-onset GHD patients by geometric remodeling: an observational case-control study

BackgroundMost patients with growth hormone deficiency (GHD) show high body mass index. Overweight subjects, but GHD patients, were demonstrated to have high left ventricular mass index (LVMi) and abnormal LV geometric remodeling. We sought to study these characteristics in a group of GHD patients, in an attempt to establish the BMI-independent role of GHD.MethodsFifty-four patients, 28 F and 26 M, aged 45.9 ± 13.1, with adult-onset GHD (pituitary adenomas 48.2%, empty sella 27.8%, pituitary inflammation 5.5%, cranio-pharyngioma 3.7%, not identified pathogenesis 14.8%) were enrolled. To minimize any possible interferences of BMI on the aim of this study, the control group included 20 age- and weight-matched healthy subjects. The LV geometry was identified by the relationship between LVMi (cut-off 125 g/m2) and relative wall thickness (cut-off 0.45) at echocardiography.ResultsThere was no significant between-group difference in resting cardiac morphology and function, nor when considering age-related discrepancy. The majority of patients had normal-low LVM/LVMi, but about one fourth of them showed higher values. These findings correlated to relatively high circulating IGF-1 and systolic blood pressure at rest. The main LV geometric pattern was eccentric hypertrophy in 22% of GHD population (26% of with severe GHD) and in 15% of controls (p = NS).ConclusionThough the lack of significant differences in resting LV morphology and function, about 25% of GHD patients showed high LVMi (consisting of eccentric hypertrophy), not dissimilarly to overweight controls. This finding, which prognostic role is well known in obese and hypertensive patients, is worthy to be investigated in GHD patients through wider controlled trials.

Shear strength degradation due to flexural ductility demand in circular RC columns

An analytical model was developed to estimate the shear-strength degradation and the residual capacity of circular reinforced concrete (RC) columns subjected to seismic action. The proposed model is an upgrade of a previously proposed model for axial force