70 research outputs found
Nonrelativistic Conformal Invariance in Mesoscopic Two-Dimensional Fermi Gases
Two-dimensional Fermi gases with universal short-range interactions are known
to exhibit a quantum anomaly, where a classical scale and conformal invariance
is broken by quantum effects at strong coupling. We argue that in a quasi
two-dimensional geometry, a conformal window remains at weak interactions.
Using degenerate perturbation theory, we verify the conformal symmetry by
computing the energy spectrum of mesoscopic particle ensembles in a harmonic
trap, which separates into conformal towers formed by so-called primary states
and their center-of-mass and breathing-mode excitations, the latter having
excitation energies at precisely twice the harmonic oscillator energy. In
addition, using Metropolis importance sampling, we compute the hyperradial
distribution function of the many-body wave functions, which are predicted by
the conformal symmetry in closed analytical form. The weakly interacting Fermi
gas constitutes a system where the nonrelativistic conformal symmetry can be
revealed using elementary methods, and our results are testable in current
experiments on mesoscopic Fermi gases.Comment: 7 pages, 4 figures + 9 pages of Supplemental Materia
Scale and conformal invariance in rotating few-fermion systems
We show that rotating two-dimensional Fermi gases possess a nonrelativistic
scale and conformal invariance at weak interactions, where the scale invariance
of universal short-range interactions is not broken by quantum effects. We
demonstrate the symmetry in the excitation spectrum of few-fermion ensembles in
a harmonic trap obtained by exact diagonalization, which are constrained by the
operator-state correspondence. The excitation spectrum is shown to split in a
set of primary states, the energies of which correspond to scaling dimensions
of conformal operators, and derived excited states that consist of breathing
modes as well as two different center-of-mass excitations, which describe
cyclotron and guiding-center excitations of the total particle cloud.
Furthermore, the conformal symmetry is manifest in the many-body wave function,
where it dictates the form of the hyperradial component, which we demonstrate
using Monte Carlo sampling of few-body wave functions.Comment: 16 pages, 10 figure
Interface dipoles of organic molecules on Ag(111) in hybrid density-functional theory
We investigate the molecular acceptors 3,4,9,10-perylene-tetracarboxylic acid
dianhydride (PTCDA), 2,3,5,6-tetra uoro-7,7,8,8-tetracyanoquinodimethane
(F4TCNQ), and 4,5,9,10-pyrenetetraone (PYTON) on Ag(111) using
densityfunctional theory. For two groups of the HSE(\alpha, \omega) family of
exchange-correlation functionals (\omega = 0 and \omega = 0.2\AA) we study the
isolated components as well as the combined systems as a function of the amount
of exact-exchange (\alpha). We find that hybrid functionals favour electron
transfer to the adsorbate. Comparing to experimental work-function data, we
report for (\alpha) ca. 0.25 a notable but small improvement over (semi)local
functionals for the interface dipole. Although Kohn-Sham eigenvalues are only
approximate representations of ionization energies, incidentally, at this value
also the density of states agrees well with the photoelectron spectra. However,
increasing (\alpha) to values for which the energy of the lowest unoccupied
molecular orbital matches the experimental electron affinity in the gas phase
worsens both the interface dipole and the density of states. Our results imply
that semi-local DFT calculations may often be adequate for conjugated organic
molecules on metal surfaces and that the much more computationally demanding
hybrid functionals yield only small improvements.Comment: submitted to New Journal of Physics (2013). More information can be
found at
http://th.fhi-berlin.mpg.de/site/index.php?n=Publications.Publication
Trypillia megasites west of the River Southern Buh: Preliminary results of Bilyi Kamin site investigation in 2018
In Bilyi Kamin, Ukraine, a Trypillia megasite of the Chechelnyk group west of the River Southern Buh was systematically investigated by high-resolution magnetometry, targeted excavations and radiometric dating. These new data make it possible to discuss afresh the significance of these large settlements and their relation to the already much longer intensively investigated megasites of the Southern Buh-Dnipro interfluve. The research confirmed that the settlement Bilyi Kamin had an extraordinary size of almost 100 ha and undoubtedly was of a carefully planned character. In order to realise a settlement of this size in the hilly landscape, enormous height differences within the settlement were accepted. Apparently, the intention to place three monumental integrative buildings on a promontory, widely visible from afar, played a decisive role. The study includes a detailed examination of the architecture and find materials of a dwelling. Compared to settlements of the Southern Buh-Dnipro interfluve, these investigations reveal, among other things, differences in waste disposal and similarities in architectural features. In the wider context, the newly obtained dating results from Bilyi Kamin seem to indicate that the peak of population concentration in Trypillia giant settlements in the region west of the River Southern Buh was already passed around 3800/3750 BCE. By contrast, this agglomeration process continued in the Southern Buh-Dnipro interfluve until about 3650 BCE. As possible reasons for these different trajectories differences in social organisation are taken into account
What are the consequences of the AWG-projections for the adequacy of social security pensions? ENEPRI Research Report No. 65, 16 January 2009
This paper starts by describing the model MIDAS in detail. It next presents and discusses some simulation results for Belgium, Germany and Italy. Finally, the simulation results of two alternative policy scenarios are presented and discussed
Why is d-wave pairing in HTS robust in the presence of impurities?
In the recent theory of strong correlations by Kulic and Zeyher it has been
shown that by lowering doping concentration a forward peak in the charge
scattering channel is developed. Accordingly, near the optimal doping the
nonmagnetic scattering is pronounced in the d-channel and its effect on d-wave
pairing is reduced. As a consequence, d-wave pairing is robust against defects
and impurities, the order parameter keeps its d-wave shape for any scattering
rate and the density of states becomes finite at the Fermi surface. For large
doping scattering anisotropy parameter is small and d-wave loses its
robustness. The theory is generally formulated for the bi-layer model by
including: 1) intra- and inter-plane pairing; 2) intra- and inter-plane
impurities.Comment: Complete revision, 4 pages with 2 PS figures, RevTeX, submitted to
Phys. Rev. Let
Magnetic Resonance Imaging-Based Robotic Radiosurgery of Arteriovenous Malformations
Objective: CyberKnife offers CT- and MRI-based treatment planning without the need for stereotactically acquired DSA. The literature on CyberKnife treatment of cerebral AVMs is sparse. Here, a large series focusing on cerebral AVMs treated by the frameless CyberKnife stereotactic radiosurgery (SRS) system was analyzed.
Methods: In this retrospective study, patients with cerebral AVMs treated by CyberKnife SRS between 2005 and 2019 were included. Planning was MRI- and CT-based. Conventional DSA was not coregistered to the MRI and CT scans used for treatment planning and was only used as an adjunct. Obliteration dynamics and clinical outcome were analyzed.
Results: 215 patients were included. 53.0% received SRS as first treatment; the rest underwent previous surgery, embolization, SRS, or a combination. Most AVMs were classified as Spetzler-Martin grade I to III (54.9%). Hemorrhage before treatment occurred in 46.0%. Patients suffered from headache (28.8%), and seizures (14.0%) in the majority of cases. The median SRS dose was 18 Gy and the median target volume was 2.4 cm³. New neurological deficits occurred in 5.1% after SRS, with all but one patient recovering. The yearly post-SRS hemorrhage incidence was 1.3%. In 152 patients who were followed-up for at least three years, 47.4% showed complete AVM obliteration within this period. Cox regression analysis revealed Spetzler-Martin grade (P = 0.006) to be the only independent predictor of complete obliteration.
Conclusions: Although data on radiotherapy of AVMs is available, this is one of the largest series, focusing exclusively on CyberKnife treatment. Safety and efficacy compared favorably to frame-based systems. Non-invasive treatment planning, with a frameless SRS robotic system might provide higher patient comfort, a less invasive treatment option, and lower radiation exposure
Effect of ABCG2, OCT1, and ABCB1(MDR1) Gene Expression on Treatment-Free Remission in a EURO-SKI Subtrial
Introduction
Tyrosine kinase inhibitors (TKIs) can safely be discontinued in chronic myeloid leukemia (CML) patients with sustained deep molecular response. ABCG2 (breast cancer resistance protein), OCT1 (organic cation transporter 1), and ABCB1 (multidrug resistance protein 1) gene products are known to play a crucial role in acquired pharmacogenetic TKI resistance. Their influence on treatment-free remission (TFR) has not yet been investigated.
Materials and Methods
RNA was isolated on the last day of TKI intake from peripheral blood leukocytes of 132 chronic phase CML patients who discontinued TKI treatment within the European Stop Tyrosine Kinase Inhibitor Study trial. Plasmid standards were designed including subgenic inserts of OCT1, ABCG2, and ABCB1 together with GUSB as reference gene. For expression analyses, quantitative real-time polymerase chain reaction was used. Multiple Cox regression analysis was performed. In addition, gene expression cutoffs for patient risk stratification were investigated.
Results
The TFR rate of 132 patients, 12 months after TKI discontinuation, was 54% (95% confidence interval [CI], 46%-62%). ABCG2 expression (‰) was retained as the only significant variable (P = .02; hazard ratio, 1.04; 95% CI, 1.01-1.07) in multiple Cox regression analysis. Only for the ABCG2 efflux transporter, a significant cutoff was found (P = .04). Patients with an ABCG2/GUSB transcript level >4.5‰ (n = 93) showed a 12-month TFR rate of 47% (95% CI, 37%-57%), whereas patients with low ABCG2 expression (≤4.5‰; n = 39) had a 12-month TFR rate of 72% (95% CI, 55%-82%).
Conclusion
In this study, we investigated the effect of pharmacogenetics in the context of a CML treatment discontinuation trial. The transcript levels of the efflux transporter ABCG2 predicted TFR after TKI discontinuation
Virtual pathway explorer (viPEr) and pathway enrichment analysis tool (PEANuT): creating and analyzing focus networks to identify cross-talk between molecules and pathways
BACKGROUND: Interpreting large-scale studies from microarrays or next-generation sequencing for further experimental testing remains one of the major challenges in quantitative biology. Combining expression with physical or genetic interaction data has already been successfully applied to enhance knowledge from all types of high-throughput studies. Yet, toolboxes for navigating and understanding even small gene or protein networks are poorly developed. RESULTS: We introduce two Cytoscape plug-ins, which support the generation and interpretation of experiment-based interaction networks. The virtual pathway explorer viPEr creates so-called focus networks by joining a list of experimentally determined genes with the interactome of a specific organism. viPEr calculates all paths between two or more user-selected nodes, or explores the neighborhood of a single selected node. Numerical values from expression studies assigned to the nodes serve to score identified paths. The pathway enrichment analysis tool PEANuT annotates networks with pathway information from various sources and calculates enriched pathways between a focus and a background network. Using time series expression data of atorvastatin treated primary hepatocytes from six patients, we demonstrate the handling and applicability of viPEr and PEANuT. Based on our investigations using viPEr and PEANuT, we suggest a role of the FoxA1/A2/A3 transcriptional network in the cellular response to atorvastatin treatment. Moreover, we find an enrichment of metabolic and cancer pathways in the Fox transcriptional network and demonstrate a patient-specific reaction to the drug. CONCLUSIONS: The Cytoscape plug-in viPEr integrates –omics data with interactome data. It supports the interpretation and navigation of large-scale datasets by creating focus networks, facilitating mechanistic predictions from –omics studies. PEANuT provides an up-front method to identify underlying biological principles by calculating enriched pathways in focus networks. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-015-2017-z) contains supplementary material, which is available to authorized users
A utilização da difração de neutrões na determinação do perfil de tensões residuais em revestimentos por soldadura
- …