Precision measurement of the 7Be solar neutrino rate and absence of day-night asymmetry in Borexino

Borexino, in data taking since May 2007, is the only experiment capable to perform the measurement of low-energy solar-ν. Borexino has performed the first direct measurement of the 7Be solar-ν rate with accuracy better than 5%. The absence of day-night asymmetry of the 7Be solar-ν rate was measured with a total uncertainty of 1%. Borexino results alone reject the Low Δm2 (LOW) region of solar-ν oscillation parameters at more than 8.5 σ CL. Combined with the other solar-ν data, Borexino measurements isolate the Large Mixing Angle (LMA)- Mikheyev Smirnov Wolfenstein (MSW) solution of neutrino oscillations without assuming CPT invariance in the neutrino sector

Looking at the Sun’s core. CNO and pep solar neutrino detection in Borexino

Both the first evidences and the first discoveries of neutrino flavor transformation have come from experiments which detected neutrinos from the Sun. Observation of solar neutrinos directly addresses the theory of stellar structure and evolution, which is the basis of the standard solar models (SSMs). The Sun as a well-defined neutrino source also provides extremely important opportunities to investigate nontrivial neutrino properties such as neutrino oscillations and Mikheyev-Smirnov-Wolfenstein (MSW) effect, because of the wide range of matter density and the great distance from the Sun to the Earth. The ultra-pure Borexino detector at Laboratori Nazionali del Gran Sasso is designed to perform low-energy solar neutrino spectroscopy. Recently, the Borexino experiment has obtained the first direct evidence of the rare proton-electron-proton (pep) fusion reaction in the Sun by the detection of the neutrinos emitted in the process. Borexino has also placed the strongest limit on the flux of the neutrinos emitted in the carbon-nitrogen-oxygen (CNO) cycle. In these proceedings I will summarise the novel techniques adopted in Borexino to reduce the cosmogenic and external background contributions and I will describe the physics results obtained

The DarkSide awakens

The DarkSide program at LNGS aims to perform background-free WIMP searches using two phase liquid argon time projection chambers, with the ultimate goal of covering all parameters down to the socalled neutrino floor. One of the distinct features of the program is the use of underground argon with has a reduced content of the radioactive 39Ar compared to atmospheric argon. The DarkSide Collaboration is currently operating the DarkSide-50 experiment, the first such WIMP detector using underground argo

The sensitivity of Euro-Atlantic regimes to model horizontal resolution

There is growing evidence that the atmospheric dynamics of the Euro-Atlantic sector during winter is driven in part by the presence of quasi-persistent regimes. However, general circulation models typically struggle to simulate these with, for example, an overly weakly persistent blocking regime. Previous studies have showed that increased horizontal resolution can improve the regime structure of a model but have so far only considered a single model with only one ensemble member at each resolution, leaving open the possibility that this may be either coincidental or model dependent. We show that the improvement in regime structure due to increased resolution is robust across multiple models with multiple ensemble members. However, while the high-resolution models have notably more tightly clustered data, other aspects of the regimes may not necessarily improve and are also subject to a large amount of sampling variability that typically requires at least three ensemble members to surmount

The European project SUREBridge – A case study in Tuscany

The European project SUREBridge (Sustainable Refurbishment of Existing Bridges) is develop-ing a new concept for the refurbishment of road bridges. The proposed technique takes ad-vantage of the peculiarities of fibre-reinforced materials to perform upgrading, repair, and strengthening in an effective and efficient way in terms of resource consumption, waste produc-tion, construction time, and traffic disruption. The technique applies to bridges with reinforced concrete slab and longitudinal girders made of either reinforced concrete or steel. Longitudinal girders are strengthened by bonding carbon fibre-reinforced polymer (CFRP) laminates to their bottom surfaces. Higher structural perfor-mances are achieved by pre-stressing the CFRP laminates. The existing concrete slab is not demolished, with savings in both construction time and waste production. Instead, tailor-made glass fibre-reinforced polymer (GFRP) panels are connected to the deck to increase its overall bending strength. Furthermore, GFRP panels enable the widening of the road section, if neces-sary to upgrade the bridge to increased traffic demand. This paper presents the application of the SUREBridge technique to a real bridge located in San Miniato, Tuscany, Italy. The designed intervention includes both the widening of the road section and the structural strengthening of the deck to comply with current traffic loads

Solar neutrino detection in a large volume double-phase liquid argon experiment

Precision measurements of solar neutrinos emitted by specific nuclear reaction chains in the Sun are of great interest for developing an improved understanding of star formation and evolution. Given the expected neutrino fluxes and known detection reactions, such measurements require detectors capable of collecting neutrino-electron scattering data in exposures on the order of 1 ktonne yr, with good energy resolution and extremely low background. Two-phase liquid argon time projection chambers (LAr TPCs) are under development for direct Dark Matter WIMP searches, which possess very large sensitive mass, high scintillation light yield, good energy resolution, and good spatial resolution in all three cartesian directions. While enabling Dark Matter searches with sensitivity extending to the "neutrino floor" (given by the rate of nuclear recoil events from solar neutrino coherent scattering), such detectors could also enable precision measurements of solar neutrino fluxes using the neutrino-electron elastic scattering events. Modeling results are presented for the cosmogenic and radiogenic backgrounds affecting solar neutrino detection in a 300 tonne (100 tonne fiducial) LAr TPC operating at LNGS depth (3,800 meters of water equivalent). The results show that such a detector could measure the CNO neutrino rate with ~15% precision, and significantly improve the precision of the 7Be and pep neutrino rates compared to the currently available results from the Borexino organic liquid scintillator detector.Comment: 21 pages, 7 figures, 6 table

Assessing mid-latitude dynamics in extreme event attribution systems

Atmospheric modes of variability relevant for extreme temperature and precipitation events are evaluated in models currently being used for extreme event attribution. A 100 member initial condition ensemble of the global circulation model HadAM3P is compared with both the multi-model ensemble from the Coupled Model Inter-comparison Project, Phase 5 (CMIP5) and the CMIP5 atmosphere-only counterparts (AMIP5). The use of HadAM3P allows for huge ensembles to be computed relatively fast, thereby providing unique insights into the dynamics of extremes. The analysis focuses on mid Northern Latitudes (primarily Europe) during winter, and is compared with ERA-Interim reanalysis. The tri-modal Atlantic eddy-driven jet distribution is remarkably well captured in HadAM3P, but not so in the CMIP5 or AMIP5 multi-model mean, although individual models fare better. The well known underestimation of blocking in the Atlantic region is apparent in CMIP5 and AMIP5, and also, to a lesser extent, in HadAM3P. Pacific blocking features are well produced in all modeling initiatives. Blocking duration is biased towards models reproducing too many short-lived events in all three modelling systems. Associated storm tracks are too zonal over the Atlantic in the CMIP5 and AMIP5 ensembles, but better simulated in HadAM3P with the exception of being too weak over Western Europe. In all cases, the CMIP5 and AMIP5 performances were almost identical, suggesting that the biases in atmospheric modes considered here are not strongly coupled to SSTs, and perhaps other model characteristics such as resolution are more important. It is recommended that rather than taking statistics over the entire CMIP5 or AMIP5 available models, only models capable of producing the relevant dynamical phenomena be employed for event attribution analyses

Euro-Atlantic weather regimes in the PRIMAVERA coupled climate simulations: impact of resolution and mean state biases on model performance

Recently, much attention has been devoted to better understand the internal modes of variability of the climate system. This is particularly important in mid-latitude regions like the North-Atlantic, which is characterized by a large natural variability and is intrinsically difficult to predict. A suitable framework for studying the modes of variability of the atmospheric circulation is to look for recurrent patterns, commonly referred to as Weather Regimes. Each regime is characterized by a specific large-scale atmospheric circulation pattern, thus influencing regional weather and extremes over Europe. The focus of the present paper is the study of the Euro-Atlantic wintertime Weather Regimes in the climate models participating to the PRIMAVERA project. We analyse here the set of coupled historical simulations (hist-1950), which have been performed both at standard and increased resolution, following the HighresMIP protocol. The models’ performance in reproducing the observed Weather Regimes is assessed in terms of different metrics, focussing on systematic biases and on the impact of resolution. We also analyse the connection of the Weather Regimes with the Jet Stream latitude and blocking frequency over the North-Atlantic sector. We find that—for most models—the regime patterns are better represented in the higher resolution version, for all regimes but the NAO-. On the other side, no clear impact of resolution is seen on the regime frequency of occurrence and persistence. Also, for most models, the regimes tend to be more tightly clustered in the increased resolution simulations, more closely resembling the observed ones. However, the horizontal resolution is not the only factor determining the model performance, and we find some evidence that biases in the SSTs and mean geopotential field might also play a role

Reactivity during bench-scale combustion of biomass fuels for carbon capture and storage applications

Reactivities of four biomass samples were investigated in four combustion atmospheres using non-isothermal thermogravimetric analysis (TGA) under two heating rates. The chosen combustion atmospheres reflect carbon capture and storage (CCS) applications and include O2O2 and CO2CO2-enrichment. Application of the Coats–Redfern method assessed changes in reactivity. Reactivity varied due to heating rate: the reactivity of char oxidation was lower at higher heating rates while devolatilisation reactions were less affected. In general, and particularly at the higher heating rate, increasing [O2O2] increased combustion reactivity. A lesser effect was observed when substituting N2N2 for CO2CO2 as the comburent; in unenriched conditions this tended to reduce char oxidation reactivity while in O2O2-enriched conditions the reactivity marginally increased. Combustion in a typical, dry oxyfuel environment (30% O2O2, 70% CO2CO2) was more reactive than in air in TGA experiments. These biomass results should interest researchers seeking to understand phenomena occurring in larger scale CCS-relevant experiments

Modes of climate variability bridge proximate and evolutionary mechanisms of masting

There is evidence that variable and synchronous reproduction in seed plants (masting) correlates to modes of climate variability, e.g. El Niño Southern Oscillation and North Atlantic Oscillation. In this perspective, we explore the breadth of knowledge on how climate modes control reproduction in major masting species throughout Earth's biomes. We posit that intrinsic properties of climate modes (periodicity, persistence and trends) drive interannual and decadal variability of plant reproduction, as well as the spatial extent of its synchrony, aligning multiple proximate causes of masting through space and time. Moreover, climate modes force lagged but in-phase ecological processes that interact synergistically with multiple stages of plant reproductive cycles. This sets up adaptive benefits by increasing offspring fitness through either economies of scale or environmental prediction. Community-wide links between climate modes and masting across plant taxa suggest an evolutionary role of climate variability. We argue that climate modes may ‘bridge’ proximate and ultimate causes of masting selecting for variable and synchronous reproduction. The future of such interaction is uncertain: processes that improve reproductive fitness may remain coupled with climate modes even under changing climates, but chances are that abrupt global warming will affect Earth's climate modes so rapidly as to alter ecological and evolutionary links. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’