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In G. Pernigotti, F. Patuzzi, A. Prada, V. Corrado & A. Gasparella (Eds.), Building Simulation Applications BSA 2022 (pp. 129–136).

This paper uses a structural, large dimensional factor model to evaluate the role of 'news' shocks (shocks with a delayed effect on productivity) in generating the business cycle. We find that (i) existing small-scale VECM models are affected by 'non-fundamentalness' and therefore fail to recover the correct shock and impulse response functions; (ii) news shocks have a limited role in explaining the business cycle; (iii) their effects are in line with what predicted by standard neoclassical theory; (iv) the bulk of business cycle fluctuations are explained by shocks unrelated to technology.

We study the design of monetary policy in an estimated model with sticky prices, search and matching frictions, and staggered nominal wage bargaining. We find that the estimated natural rate of unemployment is consistent with the NBER description of the U.S. business cycle, and that the inflation/unemployment trade-off facing monetary policymakers is quantitatively important. We also show that parameter uncertainty has a limited effect on the performance or design of monetary policy, while natural rate uncertainty has more sizeable effects. Nevertheless, policy rules that respond to the output or unemployment gaps are more efficient than rules responding to output or unemployment growth rates, also in the presence of uncertainty about the natural rates.

This paper addresses the issue of forecasting the term structure. We provide a unified state-space modelling framework that encompasses different existing discrete-time yield curve models. Within such framework we analyze the impact on forecasting performance of two crucial modelling choices, i.e. the imposition of no-arbitrage restrictions and the size of the information set used to extract factors. Using US yield curve data, we find that: a. macro factors are very useful in forecasting at medium/long forecasting horizon; b. financial factors are useful in short run forecasting; c. no-arbitrage models are effective in shrinking the dimensionality of the parameter space and, when supplemented with additional macro information, are very effective in forecasting; d. within no-arbitrage models, assuming time-varying risk price is more favourable than assuming constant risk price for medium horizon-maturity forecast when yield factors dominate the information set, and for short horizon and long maturity forecast when macro factors dominate the information set; e. however, given the complexity and the highly non-linear parameterization of no-arbitrage models, it is very difficult to exploit within this type of models the additional information offered by large macroeconomic datasets.

We investigate identifiability issues in DSGE models and their consequences for parameter estimation and model evaluation when the objective function measures the distance between estimated and model impulse responses. We show that observational equivalence, partial and weak identification problems are widespread, that they lead to biased estimates, unreliable t-statistics and may induce investigators to select false models. We examine whether different objective functions affect identification and study how small samples interact with parameters and shock identification. We provide diagnostics and tests to detect identification failures and apply them to a state-of-the-art model.

This Paper proposes a new framework to analyse systematic and unsystematic monetary policy within the same econometric model. As in Bernanke and Boivin, 2001, the model aims at capturing the following facts: monetary authorities use information from a large number of data series to extract a signal on current economic activity, which is typically measured with error. Due to strong collinearity between macroeconomic time series, relevant information is obtained by regressing the observables on few aggregates. Collinearity implies that a large panel of time series, which constitutes the information available to policy makers, can be represented as a dynamic factor model {it a la} Forni and Reichlin, 1998, Stock and Watson, 1999 and Forni et al., 2000. Here we show how, in this framework, shocks can be identified structurally and the parameters of monetary policy rules, conditional on these shocks, can be estimated. Our results for the US economy between 1982 and 2001 show that: (i) Two shocks capture 80% of the variance of key variables such as output and inflation at all horizons; (ii) The monetary shock mainly affects the term structure of interest rates, but has virtually no effect on output and inflation so that monetary policy affects the economy through its systematic behavior rather than by surprising agents; (iii) Since demand and technology have been the main forces for the dynamics of cyclical output and inflation during the Greenspan era, while supply shocks have been negligible, monetary authorities did not face any tradeoff between inflation and output. By stabilizing inflation conditionally on demand shocks, they also achieved output stabilization; (iv) Conditionally on demand, Greenspan followed the Taylor principle while, conditionally on technology, monetary policy did not respond; (v) Systematic monetary policy had a substantial role in output and inflation stabilization.

Active galactic nuclei (AGN) are massive black holes (BHs) caught in the act of accreting gas at the centre of their host galaxies. Part of the accreting mass is converted to energy and released into the surrounding medium, in a process loosely referred to as AGN feedback. Most numerical simulations include AGN feedback as a sub-grid model, wherein energy or momentum (or both) is coupled to the nearby gas. In this work, we implement a new momentum-driven model in the hydrodynamics code GIZMO, in which accretion from large scales is mediated by a sub-grid accretion disc model, and gas particles are stochastically kicked over a bi-conical region, to mimic observed kinetic winds. The feedback cone's axis can be set either parallel to the angular momentum of the gas surrounding the BH or to the BH spin direction, which is self-consistently evolved within the accretion-disc model. Using a circumnuclear disc (CND) as a test bed, we find that (i) the conical shape of the outflow is always visible and is weakly dependent on the launching orientation and aperture, resulting in comparable mass inflows and outflows; (ii) the cone's orientation is also similar amongst our tests, and it is not always the same as the initial value, due to the interaction with the CND playing a crucial role in shaping the outflow; and (iii) the velocity of the outflow, instead, differs and strongly depends on the interplay with the CND., Comment: 14 pages, 6 figures, accepted for publication in MNRAS. Updated with published version, minimal changes

The occurrence of old-growth forests is quite limited in Mediterranean islands, which have been subject to particularly pronounced human impacts. Little is known about the carbon stocks of such peculiar ecosystems compared with different stages of secondary succession. We investigated the carbon variation in aboveground woody biomass, in litter and soil, and the nitrogen variation in litter and soil, in a 100 years long secondary succession in Mediterranean ecosystems. A vineyard, three stages of plant succession (high maquis, maquis-forest, and forest-maquis), and an old growth forest were compared. Soil samples at two soil depths (0-15 and 15-30 cm), and two litter types, relatively undecomposed and partly decomposed, were collected. Carbon stock in aboveground woody biomass increased from 6 Mg ha-1 in the vineyard to 105 Mg ha-1 in old growth forest. Along the secondary succession, soil carbon considerably increased from about 33 Mg ha-1 in the vineyard to about 69 Mg ha-1 in old growth forest. Soil nitrogen has more than doubled, ranging from 4.1 Mg ha-1 in the vineyard to 8.8 Mg ha-1 in old growth forest. Both soil parameters were found to be affected by successional stage and soil depth but not by their interaction. While the C/N ratio in the soil remained relatively constant during the succession, the C/N ratio of the litter strongly decreased, probably following the progressive increase in the holm oak contribution. While carbon content in litter decreased along the succession, nitrogen content slightly increased. Overall, carbon stock in aboveground woody biomass, litter and soil increased from about 48 Mg ha-1 in the vineyard to about 198 Mg ha-1 in old growth forest. The results of this study indicate that, even in Mediterranean environments, considerable amounts of carbon may be stored through secondary succession processes up to old growth forest. The occurrence of old-growth forests is quite limited in Mediterranean islands, which have been subject to particularly pronounced human impacts. Little is known about the carbon stocks of such peculiar ecosystems compared with different stages of secondary succession. We investigated the carbon variation in aboveground woody biomass, in litter and soil, and the nitrogen variation in litter and soil, in a 100 years long secondary succession in Mediterranean ecosystems. A vineyard, three stages of plant succession (high maquis, maquis-forest, and forest-maquis), and an old growth forest were compared. Soil samples at two soil depths (0-15 and 15-30 cm), and two litter types, relatively undecomposed and partly decomposed, were collected. Carbon stock in aboveground woody biomass increased from 6 Mg ha(-1) in the vineyard to 105 Mg ha(-1) in old growth forest. Along the secondary succession, soil carbon considerably increased from about 33 Mg ha(-1) in the vineyard to about 69 Mg ha(-1) in old growth forest. Soil nitrogen has more than doubled, ranging from 4.1 Mg ha(-1) in the vineyard to 8.8 Mg ha(-1) in old growth forest. Both soil parameters were found to be affected by successional stage and soil depth but not by their interaction. While the C/N ratio in the soil remained relatively constant during the succession, the C/N ratio of the litter strongly decreased, probably following the progressive increase in the holm oak contribution. While carbon content in litter decreased along the succession, nitrogen content slightly increased. Overall, carbon stock in aboveground woody biomass, litter and soil increased from about 48 Mg ha(-1) in the vineyard to about 198 Mg ha(-1) in old growth forest. The results of this study indicate that, even in Mediterranean environments, considerable amounts of carbon may be stored through secondary succession processes up to old growth forest.

Background— Repolarization and its stability are exquisitely sensitive to I Kr features. Information on the relative importance of specific I Kr abnormalities is missing and would assist in the evaluation of arrhythmogenic risk. Methods and Results— In single guinea-pig myocytes, endogenous I Kr was replaced by modeled I Kr (m I Kr ) by dynamic clamp (DC) at a cycle length of 1 s. m I Kr parameters were systematically modified, and the resulting changes in action potential duration (APD) and its short term variability (SD1) were measured. We observed that (1) I Kr blockade increased SD1 more than expected by its dependency on APD; (2) m I Kr completely reversed APD and SD1 changes caused by I Kr blockade; (3) repolarization was most sensitive to inactivation shifts, which affected APD and SD1 concordantly; (4) activation shifts of the same magnitude had marginal impact on APD, but only when reducing m I Kr , they significantly increased SD1; (5) changes in maximal conductance resulted in a pattern similar to that of activation shifts. Conclusions— The largest effect on repolarization and its stability are expected from changes in I Kr inactivation. APD is less sensitive to changes in other I Kr gating parameters, which are better revealed by SD1 changes. SD1 may be more sensitive than APD in detecting I Kr -dependent repolarization abnormalities.

Background: The cardiac action potential (AP) shape is a species-dependent feature related to differences in ionic currents underlying repolarization. In guinea pigs (GP), dogs and humans, the AP is prolonged by a pronounced plateau phase. In canine and human, but not GP, myocytes, a spike-and-dome profile characterizes repolarization of specific regions within the heart and to a different extent according to heart rate. It is unclear whether the response to β-adrenergic stimulation is dictated by peculiarities of ion channels properties, or may results from differences in AP contour.Aim: The aim of this project is to test whether the presence of the spike-and-dome in the AP contour is, by itself, able to modify the response of membrane current to β-adrenergic stimulation in a rate-dependent fashion.Methods: We performed AP-clamp on GP myocytes with dog epicardial and endocardial AP waveforms to assess the contribution of the spike-and-dome in isoprenaline (ISO) sensitive current (IISO) at diastolic intervals (DI) of 1750ms and 300ms. We also performed dynamic clamp experiments on GP myocytes with a computational simulated canine transient outward current (Ito) to evaluate the ISO response on the AP duration (APD) in presence of an artificial spike-and-dome.Results: We found that: 1) At DI1750, IISO is more inward with dog endocardial rather than epicardial waveform; this difference was not evidenced at DI300. 2) The injection of a simulated canine Ito is not sufficient by itself to affect the direction of APD changes during β-adrenergic stimulation.Conclusions: The differences between dog and GP in setting β-adrenergic stimulation response are a species-dependent feature not only related to Ito and might be explained as a more complex mechanism involving AP shape and a diverse contribution of Ca2+ and K+ channels during the AP.

Background: Loss of the rapid delayed rectifier K+ current (IKr) leads to remarkable action potential duration (APD) prolongation and instability (measured by its short term variability; BVR). It is unknown whether APD and its BVR can be separately modulated and which among IKr gating properties is more influential in determining them.Aims: to investigate 1) whether the effects of IKr blockade (by E4031) on APD and BVR are necessarily concordant; 2) the sensitivity of APD and BVR to changes in specific IKr gating parameters.Methods: a numerical IKr model (mIKr) was constructed to fit E4031-sensitive current, previously recorded under AP-clamp conditions in guinea-pig ventricular myocytes. Native IKr was blocked by E4031 and replaced by mIKr under Dynamic-Clamp (DC) conditions. Once established that mIKr was able to fully revert the effect of E4031 on APD and BVR, we tested the effect of negative and positive changes in its gating parameters. Maximal conductance (gmax), mid-potentials activation (V0.5A) and inactivation (V0.5I) and activation/deactivation time-constant (tau) were considered.Results: E4031 increased APD and BVR. mIKr injection restored APD and BVR (NS vs control). Shifts in V0.5I changed APD and BVR concordantly, both being increased for a −15 mV shift and decreased for +15 mV one. On the other hand, a +15 mV shift of V0.5A or a 35% reduction in gmax increased BVR without affecting APD significantly. Changes in tau (±50%), did not affect APD and BVR significantly, but an opposite trend was observed for the two variables.Conclusions: 1) restoration of the control APD and BVR by mIKr indicates that known IKr properties are adequate to account for IKr impact repolarization and its stability; 2) APD and BVR tend to change concordantly but they may be independently affected by changes in gating properties.