719 research outputs found
Determinants of Climbing Performance: When Finger Flexor Strength and Endurance Count
No full textMarcolin, G, Faggian, S, Muschietti, M, Matteraglia, L, and Paoli, A. Determinants of climbing performance: when finger flexor strength and endurance count. J Strength Cond Res XX(X): 000-000, 2020-Aim of the study was: (a) to compare finger flexor strength and endurance among climbers and nonclimbers; (b) to predict climbers' level of ability using climbing-specific strength tests and prolonged fatigue protocols. 17 advanced climbers (ADV), 17 intermediate climbers (INT), and 15 nonclimbers (NOCLIMB) performed a maximal finger grip test on a climbing-specific device, a maximal handgrip test, 20 intermittent isometric maximal contractions (E1), a suspension test on a bar till exhaustion, and again 20 intermittent isometric maximal contractions (E2). Strength values were normalized to body weight (%BW). The handgrip test failed to discriminate ADV from INT. Maximal finger flexor strength differed among ADV (59.90 ± 9.42 %BW), INT (46.75 ± 8.40 %BW) and NOCLIMB (36.40 ± 6.51 %BW) (p < 0.0001; ηp: 0.586). ADV showed the best suspension time (58.55 ± 14.87 seconds) followed by INT (32.55 ± 16.87 seconds) and NOCLIMB (17.20 ± 14.30 seconds) (p < 0.0001; ηp: 0.563). ADV showed the best endurance performance in both E1 and E2. The highest correlations with climbers' ability scores were obtained with sport-specific tests (maximal finger strength, r = 0.60, p < 0.0001; bar suspension, r = 0.69, p < 0.0001) and at the highest level of fatigue (E2, r = 0.74, p < 0.0001). Strength and endurance gain more importance in determining climbers' ability if assessed with finger specific tests and after prolonged fatigue
Maximum Principle for Linear-Convex Boundary Control Problems applied to Optimal Investment with Vintage Capital.
No full textThe paper concerns the study of the Pontryagin Maximum Principle for an infinite dimensional and infinite horizon boundary control problem for linear partial differential equations. The optimal control model has already been studied both in finite and infinite horizon with Dynamic Programming methods in a series of papers by the same author et al. [26, 27, 28, 29, 30]. Necessary and sufficient optimality conditions for open loop controls are established. Moreover the co-state variable is shown to coincide with the spatial gradient of the value function evaluated along the trajectory of the system, creating a parallel between Maximum Principle and Dynamic Programming. The abstract model applies, as recalled in one of the first sections, to optimal investment with vintage capital
Past and present of cardiocirculatory assist devices: a comprehensive critical review.
No full textDuring the last 20 years, the management of heart failure has significantly improved by means of new pharmacotherapies, more timely invasive treatments and device assisted therapies. Indeed, advances in mechanical support, namely with the development of more efficient left ventricular assist devices (LVADs), and the total artificial heart have reduced mortality and morbidity in patients awaiting transplantation, so much so, that LVADs are now approved of as a strategy for destination therapy. In this review, the authors describe in detail the current basic indications, functioning modalities, main limitations of surgical LAVDs, total artificial heart development, and percutaneous assist devices, trying to clarify this complex, but fascinating topic
GROWTH MODELS WITH EXTERNALITIES ON NETWORKS
No full textAbstract. This study examines the dynamics of capital stocks distributed among
several nodes, representing different sites of production and connected via a weighted,
directed network. The network represents the externalities or spillovers that the
production in each node generates on the capital stock of other nodes. A regulator
decides to designate some of the nodes for the production of a consumption good to
maximize a cumulative utility from consumption. It is demonstrated how the optimal
strategies and stocks depend on the productivity of the resource sites and the structure
of the connections between the sites. The best locations to host production of the
consumption good are identified per the model’s parameters and correspond to the
least central (in the sense of eigenvector centrality) nodes of a suitably redefined
network that combines both flows between nodes and the nodes’ productivity
Maximum Principle for Boundary Control Problems Arising in Optimal Investment with Vintage Capital
No full textThe paper concerns the study of the Pontryagin Maximum Principle for an infinite dimensional and infinite horizon boundary control problem for linear partial differential equations. The optimal control model has already been studied both in finite and infinite horizon with Dynamic Programming methods in a series of papers by the same author et al. [26, 27, 28, 29, 30]. Necessary and sufficient optimality conditions for open loop controls are established. Moreover the co-state variable is shown to coincide with the spatial gradient of the value function evaluated along the trajectory of the system, creating a parallel between Maximum Principle and Dynamic Programming. The abstract model applies, as recalled in one of the first sections, to optimal investment with vintage capital.Linear convex control, Boundary control, Hamilton–Jacobi–Bellman equations, Optimal investment problems, Vintage capital
On competition for spatially distributed resources in networks
No full textThis study examines the dynamics of the exploitation of a natural resource distributed among and flowing between several nodes connected via a weighted, directed network. The network represents the locations and interactions of the resource nodes. A regulator decides to designate some of the nodes as natural reserves where no exploitation is allowed. The remaining nodes are assigned (one-to-one) to players, who exploit the resource at the node. It is demonstrated how the equilibrium exploitation and resource stocks depend on the productivity of the resource sites, the structure of the connections between the sites, and the number and preferences of the agents. The best locations to host nature reserves are identified per the model's parameters and correspond to the most central (in the sense of eigenvector centrality) nodes of a suitably redefined network that considers the nodes' productivity
On Dynamic Programming in Economic Models Governed by DDEs
No full textA family of optimal control problems for economic models, where state variables are driven by delay differential equations (DDEs) and subject to constraints, is treated by Bellman's dynamic programming in infinite dimensional spaces. An existence theorem is provided for the associated Hamilton-Jacobi-Bellman (HJB) equation: the value function of the control problem solves the HJB equation in a suitable sense (although such value function cannot be computed explicitly). An AK model with vintage capital and an advertising model with delay effect are taken as examples.delay differential equations, dynamic programming,
G-CSF displays restricted ability to promote Sca-1(+) cardiac stem cell proliferation in vitro
No full textGranulocyte colony-stimulating factor (G-CSF) is a controversial chemical in cardiac cell therapy. Myocardial homing of mobilized bone marrow-derived cells is thought to play a critical role in observed G-CSF-induced cardiac repair; meanwhile, the activation of proliferative potential of cardiac stem cells (CSCs) residing in the heart is a significant challenge. The present study aims to investigate whether G-CSF receptor is expressed in adult resident Sca-1(+) CSCs and determine the effect of G-CSF treatment on the proliferation of CSCs. For cardiac cells isolation, 12-week-old male C57BL/6 mice were anesthetized in a chamber containing 2.5 % isoflurane in oxygen, euthanized by CO2 inhalation and then sacrificed by cervical dislocation. Magnetic-activated cell sorting was employed to acquire highly purified Sca-1(+) CSCs. We found that G-CSF receptor was expressed in adult resident Sca-1(+) CSCs by immunofluorescence staining and Western blotting. Exposure of Sca-1(+) cells to G-CSF in the culture medium for 72 h induced time-dependent but self-limiting cell cycle acceleration with a restricted effect on the CSC proliferation. As a result, it has provided a new insight to focus on the association between cardiac G-CSF therapy and adult resident stem cell activation. It may suggest gaining a deeper insight into the mechanisms of the interaction between CSCs and G-CSF to develop a synergistic strategy based on resident stem cell and G-CSF therapy for heart disease
Crescita e resilienza nelle isole mediterranee europee: il ruolo del turismo nel confronto con le regioni non insulari
No full textIl contributo illustra le difformità di crescita esistenti tra le economie insulari e le
altre economie regionali appartenenti agli stessi paesi, prestando particolare attenzione
alla resilienza al periodo di crisi. I risultati dell’analisi confermano l’ipotesi di fondo
che vi sia una maggiore rilevanza per le variabili legate alla domanda e all’offerta turistica
nei processi di crescita delle isole e mostrano altresì l’importanza di altre variabili
(quali le economie di agglomerazione e l’apertura commerciale). Sebbene tutte le
determinanti della crescita siano state fortemente influenzate dalla Grande Recessione,
questa sembra avere generato un più ridotto impatto negativo sulla crescita nelle isole
nel caso della domanda turistica, delle economie di agglomerazione e dell’apertura
commerciale. Tali variabili, acquistano dunque un ruolo rilevante anche nei processi di
resilienza di queste economie regionali.The paper aims at investigating the different growth patterns of island economies with
respect to other regional (mainland) economies belonging to the same countries, paying
particular attention to resilience to the crisis period. The results of the analysis suggest
high relevance of tourism demand and supply for islands growth and highlight the importance
of other variables (agglomeration economies and trade openness). Although all the
determinants of growth have been strongly affected by the Great Recession, the negative
effects on islands growth generated by the crisis seems to be smaller in the case of tourist
demand, agglomeration economies and trade openness. These variables, therefore, play
a key role also in the resilience processes of these regional economies
Preliminary experience with a new device for delayed sternal closure strategy in cardiac surgery.
No full textPurpose: Open chest management with delayed sternal closure (DSC) is a valuable strategy in the management of patients with postcardiotomy hemodynamic instability or severe coagulopathy. The conventional extemporized material available for off-label sternal stenting however may limit its efficacy. We evaluated outcomes of patients with refractory severe postcardiotomy cardiogenic shock (SPCCS) treated with DSC using a novel temporary sternal spreader (NTSS) which allows myocardial recovery by progressive controlled approximation of the sternal edges. Methods: Seven patients (4 male, mean age 66.5 ± 5 years) with refractory SPCCS showing acute hemodynamic instability at sternal closure, were implanted with the NTSS, consisting of stainless-steel branches linked to 2 diverging plates of polyether-ether ketone, whose progressive opening/closing mechanism can be controlled from outside the chest with a rotating steel wire. The sternal wound was closed by an elastic membrane to achieve a sterile field. Swan-Ganz monitoring was employed, and clinical outcomes evaluated. Results: The device was successfully implanted in all patients without device-related complications or failures. Progressive approximation of sternal edges, titrated on cardiac index values, was successfully completed allowing subsequent uneventful sternal closure in all. Mean time from SPCCS to sternal closure was 70 ± 21 hours. No patient developed infective complications or late hemodynamic instability after device removal and sternal closure. One patient (14%) died of multiorgan failure on postoperative day 9. Conclusions: Despite the limited number of patients enrolled, the NTSS proved safe and effective in allowing complete myocardial recovery after SPCCS, avoiding hemodynamic instability related to abrupt sternal closure, with no occurrence of infective complications
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