The spin-1/2 anisotropic Heisenberg-chain in longitudinal and transversal magnetic fields: a DMRG study

Using the density matrix renormalization group technique, we evaluate the low-energy spectrum (ground state and first excited states) of the anisotropic antiferromagnetic spin-one-half chain under magnetic fields. We study both homogeneous longitudinal and transversal fields as well as the influence of a transversal staggered field on opening of a spin-gap. We find that only a staggered transversal field opens a substantial gap.Comment: 6 pages, 11 figure

Partner selection supported by opaque reputation promotes cooperative behavior

Reputation plays a major role in human societies, and it has been proposed as an explanation for the evolution of cooperation. While the majority of previous studies equates reputation with a transparent and complete history of players' past decisions, in real life, reputations are often ambiguous and opaque. Using web-based experiments, we explore the extent to which opaque reputation works in isolating defectors, with and without partner selection opportunities. Our results show that low reputation works as a signal of untrustworthiness, whereas medium or high reputation are not taken into account by participants for orienting their choices. We also find that reputation without partner selection does not promote cooperative behavior; that is, defectors do not turn into cooperators only for the sake of getting a positive reputation. Finally, in a third study, we find that, when reputation is pivotal to selection, then a substantial proportion of would-be defectors turn into cooperators. Taken together, these results provide insights on the characteristics of reputation and on the way in which humans make use of it when selecting partners but also when knowing that they will be selected

Na2V3O7, a frustrated nanotubular system with spin-1/2 diamond rings

Following the recent discussion on the puzzling nature of the interactions in the nanotubular system Na2V3O7, we present a detailed ab-initio microscopic analysis of its electronic and magnetic properties. By means of a non-trivial downfolding study we propose an effective model in terms of tubes of nine-site rings with the geometry of a spin-diamond necklace with frustrated inter-ring interactions. We show that this model provides a quantitative account of the observed magnetic behavior.Comment: 5 pages, 5 figures. Phys. Rev. Lett. (in press

Analisi multitemporale delle relazioni tra parametri produttivi e indice di vegetazione in viticoltura

L’efficacia degli interventi agronomici dipendono dalla capacità di programmazione in termini di tempo e intensità di intervento. Questultimi aspetti possono essere calibrati tramite una corretta conoscenza delle caratteristiche produttive e qualitative dei parametric di campo e della loro variabilità nel tempo e nello spazio. La viticoltura di precisione fornisce un supporto valido alla definizione della variabilità di campo e temporale dei parametric vegetative e produttivi. Questo lavoro sintetizza due anni di viticoltura di precisione in Sicilia, nelle campagne agronomiche consotte nel 2012 e 2013 in due aziende vitivinicole “Tenute Rapitalà” e “Donnafugata”. L’indice di vegetazione normalizzato, ottenuto da immagini in multispettrale (Rapideye) acquisite nelle fasi di allegagione, pre-invaiatura e maturazione, è stato relazionato con alcuni parametri produttivi alla raccolta (zuccheri e antociani totali) nella cultivar Nero d’Avola allevata a controspalliera. Il lavoro ha lo scopo di evidenziare la forza del legame esistente nei modelli lineari di relazione tra l’indice di vegetazione ed i parametric produttivi e mettere in evidenza: 1) l’epoca migliore per acquisire le immagini da correlare con i parametri produttivi alla raccolta; 2) se le relazioni sono significative tra gli anni oppure necessitano di ricalibrazione; 3) la trasferibilità delle relazioni nello spazio. I risultati confermano le tre ipotesi indagate per il parametro “zuccheri” alla raccolta ma non tutte per “antociani totali”. Questi risultati evidenziano comunque un possible utilizzo predittivo dei modelli di relazione rilevati da satellite e la possibilità di trasferirli nello spazio, quest’ultimo aspetto necessità però di verifiche svolte in pieno campo

Timelapse

We discuss the existence in an arbitrary frame of a finite time for the transformation of an initial quantum state into another e.g. in a decay. This leads to the introduction of a timelapse $\tilde{\tau}$ in analogy with the lifetime of a particle. An argument based upon the Heisenberg uncertainty principle suggests the value of $\tilde{\tau}=1 / M_0$. Consequences for the exponential decay formula and the modifications that $\tilde{\tau}$ introduces into the Breit-Wigner mass formula are described.Comment: 5 pages [2 figs], ReV-Te

Quantum renormalization group of XYZ model in a transverse magnetic field

We have studied the zero temperature phase diagram of XYZ model in the presence of transverse magnetic field. We show that small anisotropy (0 =< Delta <1) is not relevant to change the universality class. The phase diagram consists of two antiferromagnetic ordering and a paramagnetic phases. We have obtained the critical exponents, fixed points and running of coupling constants by implementing the standard quantum renormalization group. The continuous phase transition from antiferromagnetic (spin-flop) phase to a paramagnetic one is in the universality class of Ising model in transverse field. Numerical exact diagonalization has been done to justify our results. We have also addressed on the application of our findings to the recent experiments on Cs_2CoCl_4.Comment: 5 pages, 5 figures, new references added to the present versio

Moscato Cerletti, a rediscovered aromatic cultivar with oenological potential in warm and dry areas

Baron Antonio Mendola was devoted to the study of grapevine, applying ampelography and dabbling in crosses between cultivars in order to select new ones, of which Moscato Cerletti, obtained in 1869, was the most interesting. Grillo, one of the most important white cultivars in Sicily, was ascertained to be an offspring of Catarratto Comune and Zibibbo, the same parents which Mendola claimed he used to obtain Moscato Cerletti. Thus the hypothesis of synonymy between Moscato Cerletti and Grillo or the same parentage for both sets of parents needs to be verified. In the present study, historical documents were consulted and genetic analyses and ampelographic, agronomic and qualitative characterisation carried out to determine the distinctiveness of each cultivars. These were also compared with Catarratto Comune and Zibibbo in order to establish the Moscato Cerletti pedigree. Due to their different SSR profiles, Grillo and Moscato Cerletti were confirmed as two distinct cultivars; they also differed in ripening times and sugar storage ability, as well as in the aromatic grape produced by Moscato Cerletti only. The trio genotype genetic analysis confirmed that Zibibbo is a parent of Moscato Cerletti (justifying the aromatic grape), whilst the SSR profiles did not show Catarratto Comune to be a second parent. Moscato Cerletti was found to have oenological potential in the production of sparkling muscat wines due to its ability to adapt to a changing climate in warm and dry environments and in different winegrowing regions

An ERK1/2-driven RNA-binding switch in nucleolin drives ribosome biogenesis and pancreatic tumorigenesis downstream of RAS oncogene

Oncogenic RAS signaling reprograms gene expression through both transcriptional and post‐transcriptional mechanisms. While transcriptional regulation downstream of RAS is relatively well characterized, how RAS post‐transcriptionally modulates gene expression to promote malignancy remains largely unclear. Using quantitative RNA interactome capture analysis, we here reveal that oncogenic RAS signaling reshapes the RNA‐bound proteomic landscape of pancreatic cancer cells, with a network of nuclear proteins centered around nucleolin displaying enhanced RNA‐binding activity. We show that nucleolin is phosphorylated downstream of RAS, which increases its binding to pre‐ribosomal RNA (rRNA), boosts rRNA production, and promotes ribosome biogenesis. This nucleolin‐dependent enhancement of ribosome biogenesis is crucial for RAS‐induced pancreatic cancer cell proliferation and can be targeted therapeutically to inhibit tumor growth. Our results reveal that oncogenic RAS signaling drives ribosome biogenesis by regulating the RNA‐binding activity of nucleolin and highlight a crucial role for this mechanism in RAS‐mediated tumorigenesis

High-field magnetization study of the S = 1/2 antiferromagnetic Heisenberg chain [PM Cu(NO3_3)2_2(H2_2O)2_2]n_n with a field-induced gap

We present a high-field magnetization study of the $S$ = 1/2 antiferromagnetic Heisenberg chain [PM Cu(NO$_3$)$_2$(H$_2$O)$_2$]$_n$. For this material, as result of the Dzyaloshinskii-Moriya interaction and a staggered $g$ tensor, the ground state is characterized by an anisotropic field-induced spin excitation gap and a staggered magnetization. Our data reveal the qualitatively different behavior in the directions of maximum and zero spin excitation gap. The data are analyzed via exact diagonalization of a linear spin chain with up to 20 sites and on basis of the Bethe ansatz equations, respectively. For both directions we find very good agreement between experimental data and theoretical calculations. We extract the magnetic coupling strength $J/k_B$ along the chain direction to 36.3(5) K and determine the field dependence of the staggered magnetization component $m_s$.Comment: 5 pages, 2 figures (minor changes to manuscript and figures