scholarly journals Description of continuum structures in a discrete basis: Three-body resonances and two-nucleon decays

2020 ◽  
Author(s):  
Jesus Casal ◽  
Manuela Rodríguez-Gallardo ◽  
José M. Arias ◽  
Joaquín Gómez-Camacho ◽  
Lorenzo Fortunato ◽  
...  
Keyword(s):  
Theoretical Framework ◽  
Weakly Bound ◽  
Continuum Structures ◽  
Hyperspherical Formalism ◽  
Three Body ◽  
Dipole Response ◽  
Good Agreement

Weakly bound and unbound three-body nuclei are studied by using the pseudostate method within the hyperspherical formalism. After introducing the theoretical framework, the method is applied first to the \boldsymbol{^9}9Be nucleus, showing a good agreement with the available data for its low-lying dipole response. Then, recent results on the structure and decay of the two-neutron emitters \boldsymbol{^{26}}26O and \boldsymbol{^{16}}16Be are presented. In particular, the role of the \boldsymbol{n}𝐧-\boldsymbol{n}𝐧 correlation in shaping their properties is discussed.

DINEUTRON CORRELATION IN THE GROUND STATE AND E1 EXCITATIONS OF BORROMEAN NUCLEI

2010 ◽  
Vol 25 (21n23) ◽  
pp. 1842-1845
Author(s):  
K. HAGINO ◽  
H. SAGAWA ◽  
T. OISHI
Keyword(s):  
Contact Interaction ◽  
Ground State ◽  
Energy Distributions ◽  
Weakly Bound ◽  
Density Dependent ◽  
Body Model ◽  
Dipole Excitation ◽  
Ground State Properties ◽  
Three Body

Using a three-body model with density-dependent contact interaction, we discuss the role of dineutron correlation in the ground state properties as well as in the dipole excitation of typical weakly-bound Borromean nuclei, 11 Li and 6 He . We show that, while both the nuclei manifest themselves similar strong dineutron correlations to each other in the ground state, the energy distributions for the two emitted neutrons from the dipole excitation are considerably different. We also discuss briefly the diproton correlation in a proton-rich Borromean nucleus, 17 Ne .

The role of quark exchange in the structure function of Lithium nucleus

2015 ◽  
Vol 24 (05) ◽  
pp. 1550037 ◽  
Author(s):  
M. Modarres ◽  
A. Hadian
Keyword(s):  
Structure Function ◽  
Present Calculation ◽  
Heavy Nuclei ◽  
Free Nucleon ◽  
B Values ◽  
European Muon Collaboration ◽  
Three Body ◽  
Quark Momentum ◽  
Good Agreement

The quark exchange formalism is formulated to calculate the quark momentum distribution in the iso-scalar Lithium nucleus. Then by boosting the nucleus to an infinite momentum frame, the Lithium structure function is evaluated at different nucleon "sizes", i.e., b = 0.7, 0.8, 0.9 and 1 fm and the Bjorken scale (x) values. It is shown that the Lithium structure function becomes narrower, and it is pushed to the smaller x values, as the nucleon size is increased. Similar to our previous works for three nucleon systems, the Lithium nucleus European muon collaboration (EMC) ratio decreases, as we increase the x and b values and it shows larger effect, with respect to the free nucleon and three nucleons iso-scalar nucleus. On the other hand, present calculation of the EMC ratio for Lithium nucleus shows a good agreement with the corresponding NMC data, which is available for 1.4 × 10-4 ≤ x ≤ 0.65. Since the atomic number is still small (A = 6), in this work as usual, we ignore the possibility of simultaneous exchange of quarks between more than two nucleons, which can be important as one moves to the heavy nuclei. Although, according to Hen et al., in the neutron rich nuclei the protons have a greater probability than neutrons to have momentum greater than the Fermi momentum, the three-body contribution may be suppressed.

THE BOUNDARY CONDITION MODEL APPROACH TO BORROMEAN NUCLEI

2007 ◽  
Vol 22 (20) ◽  
pp. 1469-1479
Author(s):  
CORNEL HATEGAN ◽  
REMUS AMILCAR IONESCU ◽  
HERMANN H. WOLTER
Keyword(s):  
Boundary Condition ◽  
Bound State ◽  
Weakly Bound ◽  
Condition Model ◽  
Boundary Condition Model ◽  
Resonant States ◽  
Scattering Lengths ◽  
Three Body ◽  
Model Approach

Three-body systems are studied in the framework of the Boundary Condition Model, in which the relevant interactions are expressed in terms of the scattering lengths of the two-body subsystems. We demonstrate explicitly the role of resonant states in the two-body subsystems and of multiple scattering between the constituents in producing a weakly bound three-body system, i.e. a Borromean nucleus. We obtain qualitative relations between the spatial extension of the three-body bound state, its energy, and the scattering lengths in the subsystems. The results are compared with experimental data for the Borromean nucleus 11 Li and 14 Be .

scholarly journals Cavitation Bubble Cloud Break-Off Mechanisms at Micro-Channels

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 215
Author(s):  
Paul McGinn ◽  
Daniel Pearce ◽  
Yannis Hardalupas ◽  
Alex Taylor ◽  
Konstantina Vogiatzaki
Keyword(s):  
Cavitation Bubble ◽  
Cavitation Inception ◽  
Wave Dynamics ◽  
Bubble Cloud ◽  
Cloud Dynamics ◽  
Micro Channels ◽  
Physical Insight ◽  
Cloud Process ◽  
Good Agreement

This paper provides new physical insight into the coupling between flow dynamics and cavitation bubble cloud behaviour at conditions relevant to both cavitation inception and the more complex phenomenon of flow “choking” using a multiphase compressible framework. Understanding the cavitation bubble cloud process and the parameters that determine its break-off frequency is important for control of phenomena such as structure vibration and erosion. Initially, the role of the pressure waves in the flow development is investigated. We highlight the differences between “physical” and “artificial” numerical waves by comparing cases with different boundary and differencing schemes. We analyse in detail the prediction of the coupling of flow and cavitation dynamics in a micro-channel 20 m high containing Diesel at pressure differences 7 MPa and 8.5 MPa, corresponding to cavitation inception and "choking" conditions respectively. The results have a very good agreement with experimental data and demonstrate that pressure wave dynamics, rather than the “re-entrant jet dynamics” suggested by previous studies, determine the characteristics of the bubble cloud dynamics under “choking” conditions.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

Toward a Theoretical Framework of Corporate Social Irresponsibility: Clarifying the Gray Zones Between Responsibility and Irresponsibility

2021 ◽  
pp. 000765032110159
Author(s):  
Cynthia E. Clark ◽  
Marta Riera ◽  
María Iborra
Keyword(s):  
Corporate Social Responsibility ◽  
Social Responsibility ◽  
Theoretical Framework ◽  
Conceptual Clarity ◽  
Corporate Social Irresponsibility ◽  
Corporate Social

In this conceptual article, we argue that defining corporate social responsibility (CSR) and corporate social irresponsibility (CSI) as opposite constructs produces a lack of clarity between responsible and irresponsible acts. Furthermore, we contend that the treatment of the CSR and CSI concepts as opposites de-emphasizes the value of CSI as a stand-alone construct. Thus, we reorient the CSI discussion to include multiple aspects that current conceptualizations have not adequately accommodated. We provide an in-depth exploration of how researchers define CSI and both identify and analyze three important gray zones between CSR and CSI: (a) the role of harm and benefit, (b) the role of the actor and intentionality, and (c) the role of rectification. We offer these gray zones as factors contributing to the present lack of conceptual clarity of the term CSI, as a concept in its own right, leading to difficulties that researchers and managers experience in categorizing CSI acts as distinct from CSR.

scholarly journals Negativity and Political Behavior: A Theoretical Framework for the Analysis of Negative Voting in Contemporary Democracies

2021 ◽  
pp. 147892992110001
Author(s):  
Diego Garzia ◽  
Frederico Ferreira da Silva
Keyword(s):  
Public Opinion ◽  
Political Behavior ◽  
Voting Behavior ◽  
Theoretical Framework ◽  
Negative Attitudes ◽  
Affective Component ◽  
Parliamentary Systems ◽  
Recent Developments ◽  
Rational Component

Recent developments in Western societies have motivated a growing consideration of the role of negativity in public opinion and political behavior research. In this article, we review the scant (and largely disconnected) scientific literature on negativity and political behavior, merging contributions from social psychology, public opinion, and electoral research, with a view on developing an integrated theoretical framework for the study of negative voting in contemporary democracies. We highlight that the tendency toward negative voting is driven by three partly overlapping components, namely, (1) an instrumental–rational component characterized by retrospective performance evaluations and rationalization mechanisms, (2) an ideological component grounded on long-lasting political identities, and (3) an affective component, motivated by (negative) attitudes toward parties and candidates. By blueprinting the systematic relationships between negative voting and each of these components in turn, and suggesting multiple research paths, this article aims to stimulate future studies on negative voting in multi-party parliamentary systems to motivate a better understanding of the implications of negativity in voting behavior in contemporary democracies.

scholarly journals Seasonal predictability of Mediterranean weather regimes in the Copernicus C3S systems

2021 ◽  
Author(s):  
Ignazio Giuntoli ◽  
Federico Fabiano ◽  
Susanna Corti
Keyword(s):  
Mediterranean Region ◽  
Climate Models ◽  
Reanalysis Data ◽  
Seasonal Predictability ◽  
Economic Implications ◽  
Weather Regimes ◽  
Weather Patterns ◽  
The Mediterranean ◽  
Good Agreement

AbstractSeasonal predictions in the Mediterranean region have relevant socio-economic implications, especially in the context of a changing climate. To date, sources of predictability have not been sufficiently investigated at the seasonal scale in this region. To fill this gap, we explore sources of predictability using a weather regimes (WRs) framework. The role of WRs in influencing regional weather patterns in the climate state has generated interest in assessing the ability of climate models to reproduce them. We identify four Mediterranean WRs for the winter (DJF) season and explore their sources of predictability looking at teleconnections with sea surface temperature (SST). In particular, we assess how SST anomalies affect the WRs frequencies during winter focussing on the two WRs that are associated with the teleconnections in which the signal is more intense: the Meridional and the Anticyclonic regimes. These sources of predictability are sought in five state-of-the-art seasonal forecasting systems included in the Copernicus Climate Change Services (C3S) suite finding a weaker signal but an overall good agreement with reanalysis data. Finally, we assess the ability of the C3S models in reproducing the reanalysis data WRs frequencies finding that their moderate skill increases during ENSO intense years, indicating that this teleconnection is well reproduced by the models and yields improved predictability in the Mediterranean region.

The Role of Equatorial Rossby Waves in Tropical Cyclogenesis. Part I: Idealized Numerical Simulations in an Initially Quiescent Background Environment

2010 ◽  
Vol 138 (4) ◽  
pp. 1368-1382 ◽  
Author(s):  
Jeffrey S. Gall ◽  
William M. Frank ◽  
Matthew C. Wheeler
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Phase Speed ◽  
Tropical Cyclogenesis ◽  
Initial Amplitude ◽  
Low Level ◽  
Wave Simulation ◽  
Horizontal Momentum ◽  
Good Agreement

Abstract This two-part series of papers examines the role of equatorial Rossby (ER) waves in tropical cyclone (TC) genesis. To do this, a unique initialization procedure is utilized to insert n = 1 ER waves into a numerical model that is able to faithfully produce TCs. In this first paper, experiments are carried out under the idealized condition of an initially quiescent background environment. Experiments are performed with varying initial wave amplitudes and with and without diabatic effects. This is done to both investigate how the properties of the simulated ER waves compare to the properties of observed ER waves and explore the role of the initial perturbation strength of the ER wave on genesis. In the dry, frictionless ER wave simulation the phase speed is slightly slower than the phase speed predicted from linear theory. Large-scale ascent develops in the region of low-level poleward flow, which is in good agreement with the theoretical structure of an n = 1 ER wave. The structures and phase speeds of the simulated full-physics ER waves are in good agreement with recent observational studies of ER waves that utilize wavenumber–frequency filtering techniques. Convection occurs primarily in the eastern half of the cyclonic gyre, as do the most favorable conditions for TC genesis. This region features sufficient midlevel moisture, anomalously strong low-level cyclonic vorticity, enhanced convection, and minimal vertical shear. Tropical cyclogenesis occurs only in the largest initial-amplitude ER wave simulation. The formation of the initial tropical disturbance that ultimately develops into a tropical cyclone is shown to be sensitive to the nonlinear horizontal momentum advection terms. When the largest initial-amplitude simulation is rerun with the nonlinear horizontal momentum advection terms turned off, tropical cyclogenesis does not occur, but the convectively coupled ER wave retains the properties of the ER wave observed in the smaller initial-amplitude simulations. It is shown that this isolated wave-only genesis process only occurs for strong ER waves in which the nonlinear advection is large. Part II will look at the more realistic case of ER wave–related genesis in which a sufficiently intense ER wave interacts with favorable large-scale flow features.

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