Two-to-one resonant multi-modal dynamics of horizontal/inclined cables. Part I : theoretical formulation and model validation

This paper is first of the two papers dealingwith analytical investigation of resonant multimodal dynamics due to 2:1 internal resonances in the finite-amplitude free vibrations of horizontal/inclined cables. Part I deals with theoretical formulation and validation of the general cable model. Approximate nonlinear partial differential equations of 3-D coupled motion of small sagged cables - which account for both spatio-temporal variation of nonlinear dynamic tension and system asymmetry due to inclined sagged configurations - are presented. A multidimensional Galerkin expansion of the solution ofnonplanar/planar motion is performed, yielding a complete set of system quadratic/cubic coefficients. With the aim of parametrically studying the behavior of horizontal/inclined cables in Part II [25], a second-order asymptotic analysis under planar 2:1 resonance is accomplished by the method of multiple scales. On accounting for higher-order effectsof quadratic/cubic nonlinearities, approximate closed form solutions of nonlinear amplitudes, frequencies and dynamic configurations of resonant nonlinear normal modes reveal the dependence of cable response on resonant/nonresonant modal contributions. Depending on simplifying kinematic modeling and assigned system parameters, approximate horizontal/inclined cable models are thoroughly validated by numerically evaluating statics and non-planar/planar linear/non-linear dynamics against those of the exact model. Moreover, the modal coupling role and contribution of system longitudinal dynamics are discussed for horizontal cables, showing some meaningful effects due to kinematic condensation

Problematic internet use and emotional dysregulation among young people: A literature review

Objective: In recent years scientific interest in Internet use disorders, especially among young people, has grown dramatically. Within this contemporary research field, difficulties in regulating emotions have been increasingly explored in association with problematic Internet use (PIU). Indeed, individuals who experience difficulties in emotion regulation might be more exposed to the risk of developing PIU. Therefore, the present study aimed to review the literature from the last ten years focused on the relationship between young people’s emotional dysregulation and PIU, taking into account the main variables involved in this relationship and possible gender-related differences. Method: This review included studies published between 2010 and 2020 that were indexed in major databases with the following keywords: emotion regulation, problematic Internet use, Internet addiction, social network addiction, and social media addiction. In the selection process of the studies, close attention was paid for the mean age of the involved samples that had to range between 13 and 25 years. Results: A total of 23 studies satisfied the initial inclusion criteria and were included in the present literature review. Several reviewed studies found a strong association between emotion dysregulation and both PIU and problematic social networking with controversial gender-based findings. Furthermore, the relationships among emotional dysregulation, PIU, attachment styles, and metacognitions were largely explored. Conclusions: Overall, the present review showed that problematic Internet use might represent a coping strategy to compensate for emotional regulation deficits. The lack of social support and the lack of a good parent-adolescent relationship seem to negatively affect emotional regulation abilities, which in turn increase the risk of developing PIU. Moreover, good metacognitive abilities might represent a protective factor towards emotional dysregulation and PIU. Finally, males with emotional dysregulation are likely to be more problematically engaged in Internet use than females. These results might have important practical implications to implement health prevention/promotion programs, emotion regulation-based training programmes and therapies

Pattern and degree of left ventricular remodeling following a tailored surgical approach for hypertrophic obstructive cardiomyopathy.

Background The role of a tailored surgical approach for hypertrophic cardiomyopathy (HCM) on regional ventricular remodelling remains unknown. The aims of this study were to evaluate the pattern, extent and functional impact of regional ventricular remodelling after a tailored surgical approach. Methods From 2005 to 2008, 44 patients with obstructive HCM underwent tailored surgical intervention. Of those, 14 were ineligible for cardiac magnetic resonance (CMR) studies. From the remainder, 14 unselected patients (42±12 years) underwent pre- and post-operative CMR studies at a median 12 months post-operatively (range 4-37 months). Regional changes in left ventricular (LV) thickness as well as global LV function following surgery were assessed using CMR Tools (London, UK). Results Pre-operative mean echocardiographic septal thickness was 21±4 mm and mean LV outflow gradient was 69±32 mmHg. Following surgery, there was a significant degree of regional regression of LV thickness in all segments of the LV, ranging from 16% in the antero-lateral midventricular segment to 41% in the anterior basal segment. Wall thickening was significantly increased in basal segments but showed no significant change in the midventricular or apical segments. Globally, mean indexed LV mass decreased significantly after surgery (120±29g/m2 versus 154±36g/m2; p<0.001). There was a trend for increased indexed LV end-diastolic volume (70±13 mL versus 65±11 mL; p=0.16) with a normalization of LV ejection fraction (68±7% versus 75±9%; p<0.01). Conclusion Following a tailored surgical relief of outflow obstruction for HCM, there is a marked regional reverse LV remodelling. These changes could have a significant impact on overall ventricular dynamics and function

Reinforcing the pulmonary artery autograft in the aortic position with a textile mesh: a histological evaluation

OBJECTIVES The Ross procedure involves replacing a patient’s diseased aortic valve with their own pulmonary valve. The most common failure mode is dilatation of the autograft. Various strategies to reinforce the autograft have been proposed. Personalized external aortic root support has been shown to be effective in stabilizing the aortic root in Marfan patients. In this study, the use of a similar external mesh to support a pulmonary artery autograft was evaluated. METHODS The pulmonary artery was translocated as an interposition autograft in the descending thoracic aortas of 10 sheep. The autograft was reinforced with a polyethylene terephthalate mesh (n = 7) or left unreinforced (n = 3). After 6 months, a computed tomography scan was taken, and the descending aorta was excised and histologically examined using the haematoxylin–eosin and Elastica van Gieson stains. RESULTS The autograft/aortic diameter ratio was 1.59 in the unreinforced group but much less in the reinforced group (1.11) (P < 0.05). A fibrotic sheet, variable in thickness and containing fibroblasts, neovessels and foreign body giant cells, was incorporated in the mesh. Histological examination of the reinforced autograft and the adjacent aorta revealed thinning of the vessel wall due to atrophy of the smooth muscle cells. Potential spaces between the vessel wall and the mesh were filled with oedema. CONCLUSIONS Reinforcing an interposition pulmonary autograft in the descending aorta with a macroporous mesh showed promising results in limiting autograft dilatation in this sheep model. Histological evaluation revealed atrophy of the smooth muscle cell and consequently thinning of the vessel wall within the mesh support

Personalised external aortic root support for elective treatment of aortic root dilation in 200 patients

BACKGROUND AND OBJECTIVES: In personalised external aortic root support (PEARS), a custom-made, macroporous mesh is used to stabilise a dilated aortic root and prevent dissection, primarily in patients with genetically driven aortopathies. Data are needed on the safety and postoperative incidence of aortic events. METHODS: We present a multicentre cohort study evaluating the first 200 consecutive patients (median age 33 years) undergoing surgery with an intention to perform PEARS for aortic root dilatation in 23 centres between 2004 and 2019. Perioperative outcomes were collected prospectively while clinical follow-up was retrieved retrospectively. Median follow-up was 21.2 months. RESULTS: The main indication was Marfan syndrome (73.5%) and the most frequent concomitant procedure was mitral valve repair (10%). An intervention for myocardial ischaemia or coronary injury was needed in 11 patients, 1 case resulting in perioperative death. No ascending aortic dissections were observed in 596 documented postoperative patient years. Late reoperation was performed in 3 patients for operator failure to achieve complete mesh coverage. Among patients with at least mild aortic regurgitation (AR) preoperatively, 68% had no or trivial AR at follow-up. CONCLUSIONS: This study represents the clinical history of the first 200 patients to undergo PEARS. To date, aortic dissection has not been observed in the restrained part of the aorta, yet long-term follow-up is needed to confirm the potential of PEARS to prevent dissection. While operative mortality is low, the reported coronary complications reflect the learning curve of aortic root surgery in patients with connective tissue disease. PEARS may stabilise or reduce aortic regurgitation