Long-run relationship between crop-biodiversity and cereal production under the CAP reform: evidence from Italian regions

Biodiversity has a prominent role in defining and preserving ecosystem well-being; the analysis of biodiversity effects on agricultural production is well documented. The paper offers empirical evidence on the role of intra-species biodiversity in sustaining cereal production within Italian regions, covering a time span (1989-2007) which accounts for the important CAP policy reforms. A Cobb-Douglas production function that includes both biodiversity and subsidies as control variables is estimated for 20 Italian regions, controlling for both cross-sectional heterogeneity and the dynamic structure of agricultural production. Different estimation methods are compared, including Mean Group and Pooled Mean Group estimators which allow for the possibility of potential non stationarity of the series and heterogeneous parameters across-groups. We find clear evidence of significant long-run relationships between biodiversity and cereal production; moreover, the evidence on the role of PAC intervention measures is less clear-cut, showing a potentially negative effect on production along the period under analysis that can be attributed to the aforementioned policy shift.

Long-range Ising and Kitaev Models: Phases, Correlations and Edge Modes

We analyze the quantum phases, correlation functions and edge modes for a class of spin-1/2 and fermionic models related to the 1D Ising chain in the presence of a transverse field. These models are the Ising chain with anti-ferromagnetic long-range interactions that decay with distance $r$ as $1/r^\alpha$, as well as a related class of fermionic Hamiltonians that generalise the Kitaev chain, where both the hopping and pairing terms are long-range and their relative strength can be varied. For these models, we provide the phase diagram for all exponents $\alpha$, based on an analysis of the entanglement entropy, the decay of correlation functions, and the edge modes in the case of open chains. We demonstrate that violations of the area law can occur for $\alpha \lesssim1$, while connected correlation functions can decay with a hybrid exponential and power-law behaviour, with a power that is $\alpha$-dependent. Interestingly, for the fermionic models we provide an exact analytical derivation for the decay of the correlation functions at every $\alpha$. Along the critical lines, for all models breaking of conformal symmetry is argued at low enough $\alpha$. For the fermionic models we show that the edge modes, massless for $\alpha \gtrsim 1$, can acquire a mass for $\alpha < 1$. The mass of these modes can be tuned by varying the relative strength of the kinetic and pairing terms in the Hamiltonian. Interestingly, for the Ising chain a similar edge localization appears for the first and second excited states on the paramagnetic side of the phase diagram, where edge modes are not expected. We argue that, at least for the fermionic chains, these massive states correspond to the appearance of new phases, notably approached via quantum phase transitions without mass gap closure. Finally, we discuss the possibility to detect some of these effects in experiments with cold trapped ions.Comment: 15 pages, 8 figure

Optical near-field mapping of excitons and biexcitons in naturally occurring semiconductor quantum dots

We calculate the near-field optical spectra of excitons and biexcitons in semiconductor quantum dots naturally occurring at interface fluctuations in GaAs-based quantum wells, using a non-local description of the response function to a spatially modulated electro-magnetic field. The relative intensity of the lowest, far-field forbidden excitonic states is predicted; the spatial extension of the ground biexciton state is found in agreement with recently published experiments

A multi-sphere particle numerical model for non-invasive investigations of neuronal human brain activity

In this paper, a multi-sphere particle method is built-up in order to estimate the solution of the Poisson's equation with Neumann boundary conditions describing the neuronal human brain activity. The partial differential equations governing the relationships between neural current sources and the data produced by neuroimaging technique, are able to compute the scalp potential and magnetic field distributions generated by the neural activity. A numerical approach is proposed with current dipoles as current sources and going on in the computation by avoiding the mesh construction. The current dipoles are into an homogeneous spherical domain modeling the head and the computational approach is extended to multilayered con¯guration with different conductivities. A good agreement of the numerical results is shown and, for the first time compared with the analytical ones

Field-controlled suppression of phonon-induced transitions in coupled quantum dots

We calculate the longitudinal-acoustic phonon scattering rate for a vertical double quantum dot system with weak lateral confinement and show that a strong modulation of the single-electron excited states lifetime can be induced by an external magnetic or electric field. The results are obtained for typical realistic devices using a Fermi golden rule approach and a three-dimensional description of the electronic quantum states.Comment: REVTex4 class, 6 pages, 3 figures, to be published in Applied Physics Letter

Long-run relationship between crop-biodiversity and cereal production under the CAP reform: evidence from Italian regions

Biodiversity has a prominent role in defining and preserving ecosystem well-being; the analysis of biodiversity effects on agricultural production is well documented. The paper offers empirical evidence on the role of intra-species biodiversity in sustaining cereal production within Italian regions, covering a time span (1989-2007) which accounts for the important CAP policy reforms. A Cobb-Douglas production function that includes both biodiversity and subsidies as control variables is estimated for 20 Italian regions, controlling for both cross-sectional heterogeneity and the dynamic structure of agricultural production. Different estimation methods are compared, including Mean Group and Pooled Mean Group estimators which allow for the possibility of potential non stationarity of the series and heterogeneous parameters across-groups. We find clear evidence of significant long-run relationships between biodiversity and cereal production; moreover, the evidence on the role of PAC intervention measures is less clear-cut, showing a potentially negative effect on production along the period under analysis that can be attributed to the aforementioned policy shift

Reduced electron relaxation rate in multi-electron quantum dots

We use a configuration-interaction approach and Fermi golden rule to investigate electron-phonon interaction in realistic multi-electron quantum dots. Lifetimes are computed in the low-density, highly correlated regime. We report numerical evidence that electron-electron interaction generally leads to reduced decay rates of excited electronic states in weakly confined quantum dots, where carrier relaxation is dominated by the interaction with longitudinal acoustic phonons.Comment: to appear in Phys. Rev. Let

Blood Pressure Non-Dipping and Obstructive Sleep Apnea Syndrome: A Meta-Analysis

AIM: We examined the reduced blood pressure (BP) nocturnal fall in patients with obstructive sleep apnea (OSA) by a meta-analysis including studies that provided data on prevalence rates of non-dipping (ND) pattern during 24-h ambulatory blood pressure monitoring (ABPM). DESIGN: The PubMed, OVID-MEDLINE, and Cochrane CENTRAL literature databases were searched for appropriate articles without temporal restriction up to April 2019 through focused and sensitive search methods. Studies were identified by crossing the search terms as follows: "obstructive sleep apnea", "sleep quality", "non dipping", "reduced nocturnal BP fall", "circadian BP variation", "night-time BP", and "ambulatory blood pressure monitoring". RESULTS: Meta-analysis included 1562 patients with OSA from different clinical settings and 957 non-OSA controls from 14 studies. ND pattern prevalence in patients with OSA widely varied among studies (36.0-90.0%). This was also the case for non-OSA controls (33.0% to 69.0%). Overall, the ND pattern, assessed as an event rate in the pooled OSA population, was 59.1% (confidence interval (CI): 52.0-65.0%). Meta-analysis of the seven studies comparing the prevalence of ND pattern in participants with OSA and controls showed that OSA entails a significantly increased risk of ND (Odds ratio (OR) = 1.47, CI: 1.07-1.89, p < 0.01). After the exclusion of patients with mild OSA, OR increased to 1.67 (CI: 1.21-2.28, p < 0.001). CONCLUSIONS: The present meta-analysis, extending previous information on the relationship between OSA and impaired BP dipping, based on single studies, suggests that this condition increases by approximately 1.5 times the likelihood of ND, which is a pattern associated with a greater cardiovascular risk than normal BP dipping