77 research outputs found
Long-term trends in yield variance of temperate managed grassland
The management of climate-resilient grassland systems is important for stable livestock fodder production. In the face of climate change, maintaining productivity while minimizing yield variance of grassland systems is increasingly challenging. To achieve climate-resilient and stable productivity of grasslands, a better understanding of the climatic drivers of long-term trends in yield variance and its dependence on agronomic inputs is required. Based on the Park Grass Experiment at Rothamsted (UK), we report for the first time the long-term trends in yield variance of grassland (1965â2018) in plots given different fertilizer and lime applications, with contrasting productivity and plant species diversity. We implemented a statistical model that allowed yield variance to be determined independently of yield level. Environmental abiotic covariates were included in a novel criss-cross regression approach to determine climatic drivers of yield variance and its dependence on agronomic management. Our findings highlight that sufficient liming and moderate fertilization can reduce yield variance while maintaining productivity and limiting loss of plant species diversity. Plots receiving the highest rate of nitrogen fertilizer or farmyard manure had the highest yield but were also more responsive to environmental variability and had less plant species diversity. We identified the days of water stress from March to October and temperature from July to August as the two main climatic drivers, explaining approximately one-third of the observed yield variance. These drivers helped explain consistent unimodal trends in yield varianceâwith a peak in approximately 1995, after which variance declined. Here, for the first time, we provide a novel statistical framework and a unique long-term dataset for understanding the trends in yield variance of managed grassland. The application of the criss-cross regression approach in other long-term agro-ecological trials could help identify climatic drivers of production risk and to derive agronomic strategies for improving the climate resilience of cropping systems
Strong Deformation Effects in Hot Rotating 46Ti
Exotic-deformation effects in 46Ti nucleus were investigated by analysing the
high-energy gamma-ray and the alpha-particle energy spectra. One of the
experiments was performed using the charged-particle multi-detector array ICARE
together with a large volume (4"x4") BGO detector. The study focused on
simultaneous measurement of light charged particles and gamma-rays in
coincidence with the evaporation residues. The experimental data show a
signature of very large deformations of the compound nucleus in the Jacobi
transition region at the highest spins. These results are compared to data from
previous experiments performed with the HECTOR array coupled to the EUROBALL
array, where it was found that the GDR strength function is highly fragmented,
strongly indicating a presence of nuclei with very large deformation.Comment: 10 pages, 6 figures, Proceedings of the Zakopane Conference on
Nuclear Physics, to be published in Acta Phys. Pol. B (2007
High-spin states and band terminations in v 49
High-spin states in 49 V have been studied through the 28 Si(28 Si, Îą3p) reaction using the EUROBALL Îł-ray detector array. The 49 V level scheme has been extended up to 13.1 MeV including 21 new states. Both negative and positive parity states have been interpreted in the framework of theShell Model. The 27/2â and the 31/2+ band termination states have been observed in agreement with theoretical predictions.Fil: Rodrigues Ferreira Maltez, Dario Pablo. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas; Argentina. ComisiĂłn Nacional de EnergĂa AtĂłmica. Gerencia del Ărea de InvestigaciĂłn y Aplicaciones No Nucleares. Gerencia FĂsica (Centro AtĂłmico Constituyentes). Proyecto Tandar; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de FĂsica; ArgentinaFil: Hojman, Daniel Leonardo. ComisiĂłn Nacional de EnergĂa AtĂłmica. Gerencia del Ărea de InvestigaciĂłn y Aplicaciones No Nucleares. Gerencia FĂsica (Centro AtĂłmico Constituyentes). Proyecto Tandar; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas; ArgentinaFil: Lenzi, Silvia M.. Istituto Nazionale Di Fisica Nucleare.; Italia. UniversitĂ di Padova; ItaliaFil: Cardona, Maria Angelica. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas; Argentina. ComisiĂłn Nacional de EnergĂa AtĂłmica. Gerencia del Ărea de InvestigaciĂłn y Aplicaciones No Nucleares. Gerencia FĂsica (Centro AtĂłmico Constituyentes). Proyecto Tandar; Argentina. Universidad Nacional de San MartĂn. Escuela de Ciencia y TecnologĂa; ArgentinaFil: Fernea, Enrico. UniversitĂ di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Axiotis, M.. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Beck, C.. UniversitĂŠ de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Bednarczyk, P.. Polish Academy of Sciences; ArgentinaFil: Bizzetti, P. G.. UniversitĂ di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Bizzetti Sona, A. M.. UniversitĂ di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Della Vedova, F.. UniversitĂ di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Grebosz, J.. Polish Academy of Sciences; ArgentinaFil: Haas, F.. UniversitĂŠ de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Kmiecik, M.. Polish Academy of Sciences; ArgentinaFil: Maj, A.. Polish Academy of Sciences; ArgentinaFil: MÄczyĹski, W.. Polish Academy of Sciences; ArgentinaFil: Napoli, D. R.. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Nespolo, M.. UniversitĂ di Padova; Italia. Istituto Nazionale Di Fisica Nucleare.; ItaliaFil: Papka, P.. UniversitĂŠ de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: SĂĄnchez i Zafra, A.. UniversitĂŠ de Strasbourg; Francia. Centre National de la Recherche Scientifique; FranciaFil: Styczen, J.. Polish Academy of Sciences; ArgentinaFil: Thummerer, S.. Alfred-Wegener-Institut, Helmholtz-Zentrum fĂźr Polar- und Meeresforschung; AlemaniaFil: ZiÄbliĹski, M.. Polish Academy of Sciences; Argentin
Evidence for the Jacobi shape transition in hot 46Ti
The gamma-rays from the decay of the GDR in 46Ti compound nucleus formed in
the 18O+28Si reaction at bombarding energy 105 MeV have been measured in an
experiment using a setup consisting of the combined EUROBALL IV, HECTOR and
EUCLIDES arrays. A comparison of the extracted GDR lineshape data with the
predictions of the thermal shape fluctuation model shows evidence for the
Jacobi shape transition in hot 46Ti. In addition to the previously found broad
structure in the GDR lineshape region at 18-27 MeV caused by large
deformations, the presence of a low energy component (around 10 MeV), due to
the Coriolis splitting in prolate well deformed shape, has been identified for
the first time.Comment: 8 pages, 4 figures, proceedings of the COMEX1 conference, June 2003,
Paris; to be published in Nucl. Phys.
Quantum tunneling of the excited rotational bands in the superdeformed nucleus 143Eu
The properties of the thermally excited rotational motion up to the region of rotational damping are studied experimentally in the superdeformed nucleus 143 Eu. The effective lifetime of the excited discrete rotational bands forming ridge structures in â matrices is measured at the EUROBALL array using the DSAM technique, giving a quadrupole momentQt 10 e b, consistent with the deformation of the superdeformed yrast band. In addition, the effective number of excited superdeformed bands is extracted by a statistical analysis of the ridge structure, for transition energies down to the region where the effect of the decay-out into the normal deformed well shows up. The experimental data are compared with microscopic cranked shell model calculations including a residual interaction of surface delta type. Satisfactory agreement between data and theory is obtained when the quantum tunneling of the excited superdeformed states is included in the model. Š 2001 Published by Elsevier Science B.V
Fine structure of the Gamow-Teller resonance revealed in the decay of Ho-150 2(-) isomer
The Îł rays following the 72s 150Ho 2- Gamow-Teller β decay have been investigated with the CLUSTER CUBE setup, an array of six EUROBALL CLUSTER Ge detectors in close cubic geometry, providing a Îł ray detection sensitivity of 2Ă10-5 per β-parent decay for Îł-ray energies up to 5 MeV. The fine structure of the Gamow-Teller resonance at 4.4-MeV excitation in 150Dy has been studied. The resolved levels are compared with Shell Model predictions
Long-term analysis from a cropping system perspective - Yield stability, environmental adaptability, and production risk of winter barley
In the face of climate change, the potential impacts of adverse weather conditions on the productivity and vulnerability of cropping systems (CS) worldwide constitute a key agronomic issue upon which global food security depends. To date, little information regarding how the diversity of CS or agricultural practices aďŹect the long-term yield responses of winter barley is available. The aim of this study was to investigate the impact of CS diversity in terms of cropping sequences, organic matter supplies, and nitrogen (N) fertilization on the yield vulnerability of winter barley. Yields were evaluated in terms of their stability, environmental adaptability, and production risk(probability of yield loss.Data from a 27-year experiment were statistically analysed using three mixed models giving residual maximum likelihood estimates including the Shukla stability variance index, the Finlay-Wilkinson environmental regression, and the Eskridge risk assessment approach. The results showed that winter barley grown in cropping sequences dominated by cereals had lower yield stability and environmental adaptability and greater production risks compared with winter barley grown in CS with higher crop diversity and additional organic matter inputs. When barley yields were compared at three doses of mineral N, the highest yield stability was achieved with the medium N dose (70kg N haâ1),followed by the higher level of N(140kgN haâ1). The most unstable yields with the highest production risks were observed when barley was grown without any mineral N fertilization. Overall, a higher level of crop diversity with organic matter inputs and intermediate N fertilization resulted in lower yield vulnerability in winter barley
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