2,714 research outputs found
Suppression of Dimer Correlations in the Two-Dimensional - Heisenberg Model: an Exact Diagonalization Study
We present an exact diagonalization study of the ground state of the
spin-half model. Dimer correlation functions and the susceptibility
associated to the breaking of the translational invariance are calculated for
the and the clusters. These results -- especially when
compared to the one dimensional case, where the occurrence of a dimerized phase
for large enough frustration is well established -- suggest either a
homogeneous spin liquid or, possibly, a dimerized state with a rather small
order parameter
Le fonti per gli studi ebraici tra ricerca e valorizzazione: il progetto Judaica Europeana
Il contributo presenta un recente convegno multi-disciplinare, ideato per riflettere sulle ricadute scientifiche e didattiche del progetto Judaica Europeana, promosso per raccogliere le testimonianze della cultura ebraica come ulteriore fonte del portale web europeo della Commissione europea. Il volume degli atti documenta il possibile e fruttuoso dialogo tra studiosi di vari ambiti disciplinari, impegnati nella ricerca scientifica come nell'attivit\ue0 di tutela e promozione culturale, nella convinzione che ricerca e valorizzazione (anche nello specifico della cultura ebraica) siano assolutamente inscindibili. La prima parte del volume raccoglie indagini che, interrogandosi prima di tutto sullo statuto dei cosiddetti Jewish studies, dimostrano come la cultura ebraica possa essere analizzata attraverso una straordinaria variet\ue0 di fonti, dirette o indirette. La seconda parte discute \u2013 anche dal punto di vista metodologico e attraverso diverse best practice \u2013 le possibilit\ue0 di socializzare, divulgare e ri/usare le conoscenze acquisite nella pratica della ricerca e della tutela dei beni culturali, anche alla luce delle pi\uf9 aggiornate tecnologie digitali.
The paper presents a recent multi-disciplinary conference, organised in Fermo in order to discuss on the impact of Judaica Europeana project on research and education. The proceedings of Fermo conference document the possible, fruitful dialogue among scholars of different disciplines, engaged both in scientific research and in the activities of preservation and promotion of cultural heritage. The premise was that research and management in the field of cultural heritage are absolutely inseparable. The first part of the book presents research results showing that Jewish culture can be analyzed through an extraordinary variety of direct or indirect sources. The second part discusses - from a methodological point of view and presenting different best practices - the chance to socialize, communicate and re / use the knowledge gained in the practice of research and the preservation of cultural heritage, especially adopting the latest digital technologies
Reentrant behavior of the phase stiffness in Josephson junction arrays
The phase diagram of a 2D Josephson junction array with large substrate
resistance, described by a quantum XY model, is studied by means of Fourier
path-integral Monte Carlo. A genuine Berezinskii-Kosterlitz-Thouless transition
is found up to a threshold value g* of the quantum coupling, beyond which no
phase coherence is established. Slightly below g* the phase stiffness shows a
reentrant behavior with temperature, in connection with a low-temperature
disappearance of the superconducting phase, driven by strong nonlinear quantum
fluctuations.Comment: 4 pages, 7 figures, to appear in Phys.Rev.Let
From the triangular to the kagome lattice: Following the footprints of the ordered state
We study the spin-1/2 Heisenberg model in a lattice that interpolates between
the triangular and the kagome lattices. The exchange interaction along the
bonds of the kagome lattice is J, and the one along the bonds connecting kagome
and non-kagome sites is J', so that J'=J corresponds to the triangular limit
and J'=0 to the kagome one. We use variational and exact diagonalization
techniques. We analyze the behavior of the order parameter for the
antiferromagnetic phase of the triangular lattice, the spin gap, and the
structure of the spin excitations as functions of J'/J. Our results indicate
that the antiferromagnetic order is not affected by the reduction of J' down to
J'/J ~ 0.2. Below this value, antiferromagnetic correlations grow weaker, a
description of the ground state in terms of a Neel phase renormalized by
quantum fluctuations becomes inadequate, and the finite-size spectra develop
features that are not compatible with antiferromagnetic ordering. However, this
phase does not appear to be connected to the kagome phase as well, as the
low-energy spectra do not evolve with continuity for J'-> 0 to the kagome
limit. In particular, for any non-zero value of J', the latter interaction sets
the energy scale for the low-lying spin excitations, and a gapless triplet
spectrum, destabilizing the kagome phase, is expected.Comment: 9 pages, 10 Figures. To be published in PR
ThermoScan: Semi-automatic Identification of Protein Stability Data From PubMed
open3noThis work was supported by the PRIN project, “Integrative tools for defining the molecular basis of the diseases: Computational and Experimental methods for Protein Variant Interpretation” of the Ministero Istruzione, Università e Ricerca (201744NR8S).During the last years, the increasing number of DNA sequencing and protein mutagenesis studies has generated a large amount of variation data published in the biomedical literature. The collection of such data has been essential for the development and assessment of tools predicting the impact of protein variants at functional and structural levels. Nevertheless, the collection of manually curated data from literature is a highly time consuming and costly process that requires domain experts. In particular, the development of methods for predicting the effect of amino acid variants on protein stability relies on the thermodynamic data extracted from literature. In the past, such data were deposited in the ProTherm database, which however is no longer maintained since 2013. For facilitating the collection of protein thermodynamic data from literature, we developed the semi-automatic tool ThermoScan. ThermoScan is a text mining approach for the identification of relevant thermodynamic data on protein stability from full-text articles. The method relies on a regular expression searching for groups of words, including the most common conceptual words appearing in experimental studies on protein stability, several thermodynamic variables, and their units of measure. ThermoScan analyzes full-text articles from the PubMed Central Open Access subset and calculates an empiric score that allows the identification of manuscripts reporting thermodynamic data on protein stability. The method was optimized on a set of publications included in the ProTherm database, and tested on a new curated set of articles, manually selected for presence of thermodynamic data. The results show that ThermoScan returns accurate predictions and outperforms recently developed text-mining algorithms based on the analysis of publication abstracts. Availability: The ThermoScan server is freely accessible online at https://folding.biofold.org/thermoscan. The ThermoScan python code and the Google Chrome extension for submitting visualized PMC web pages to the ThermoScan server are available at https://github.com/biofold/ThermoScan.openTurina P.; Fariselli P.; Capriotti E.Turina P.; Fariselli P.; Capriotti E
Dirac method and symplectic submanifolds in the cotangent bundle of a factorizable Lie group
In this work we study some symplectic submanifolds in the cotangent bundle of
a factorizable Lie group defined by second class constraints. By applying the
Dirac method, we study many issues of these spaces as fundamental Dirac
brackets, symmetries, and collective dynamics. This last item allows to study
integrability as inherited from a system on the whole cotangent bundle, leading
in a natural way to the AKS theory for integrable systems
Treatment responses to antiangiogenetic therapy and chemotherapy in nonsecreting paraganglioma (PGL4) of urinary bladder with SDHB mutation: a case report
Paraganglioma (PGL) is a rare neuroendocrine tumor. Currently, the malignancy is defined as the presence of metastatic spread at presentation or during follow-up. Several gene mutations are listed in the pathogenesis of PGL, among which succinate dehydrogenase (SDHX), particularly the SDHB isoform, is the main gene involved in malignancy. A 55-year-old male without evidence of catecholamine secretion had surgery for PGL of the urinary bladder. After 1 year, he showed a relapse of disease and demonstrated malignant PGL without evidence of catecholamine secretion with a germline heterozygous mutation of succinate dehydrogenase B (SDHB). After failure of a second surgery for relapse, he started medical treatment with sunitinib daily but discontinued due to serious side effects. Cyclophosphamide, vincristine, and dacarbazine (CVD) chemotherapeutic regimen stopped the disease progression for 7 months.
Conclusion: Malignant PGL is a very rare tumor, and SDHB mutations must be always considered in molecular diagnosis because they represent a critical event in the progression of the oncological disease. Currently, there are few therapeutic protocols, and it is often difficult, as this case demonstrates, to decide on a treatment option according to a reasoned set of choices.
Abbreviations: CVD = cyclophosphamide, vincristine and dacarbazine, HIF-1a = hypoxia inducible factor 1 alpha, PGL = paraganglioma, SDH = succinate dehydrogenase, VEGF = vasoendothelial growth factor
Absence of Translational Symmetry Breaking in Nonmagnetic Insulator Phase on Two-Dimensional Lattice with Geometrical Frustration
The ground-state properties of the two-dimensional Hubbard model with
nearest-neighbor and next-nearest-neighbor hoppings at half filling are studied
by the path-integral-renormalization-group method. The nonmagnetic-insulator
phase sandwiched by the the paramagnetic-metal phase and the
antiferromagnetic-insulator phase shows evidence against translational symmetry
breaking of the dimerized state, plaquette singlet state, staggered flux state,
and charge ordered state. These results support that the genuine Mott insulator
which cannot be adiabatically continued to the band insulator is realized
generically by Umklapp scattering through the effects of geometrical
frustration and quantum fluctuation in the two-dimensional system.Comment: 4 pages and 7 figure
Thermodynamics of the quantum easy-plane antiferromagnet on the triangular lattice
The classical XXZ triangular-lattice antiferromagnet (TAF) shows both an
Ising and a BKT transition, related to the chirality and the in-plane spin
components, respectively. In this paper the quantum effects on the
thermodynamic quantities are evaluated by means of the pure-quantum
self-consistent harmonic approximation (PQSCHA), that allows one to deal with
any spin value through classical MC simulations. We report the internal energy,
the specific heat, and the in-plane correlation length of the quantum XX0 TAF,
for S=1/2, 1, 5/2. The quantum transition temperatures turn out to be smaller
the smaller the spin, and agree with the few available theoretical and
numerical estimates.Comment: 4 pages,3 postscript figure
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