1,177 research outputs found
Numerical simulations of a two-dimensional lattice grain boundary model
We present detailed Monte Carlo results for a two-dimensional grain boundary
model on a lattice. The effective Hamiltonian of the system results from the
microscopic interaction of grains with orientations described by spins of unit
length, and leads to a nearest-neighbour interaction proportional to the
absolute value of the angle between the grains. Our analysis of the correlation
length xi and susceptibility chi in the high-temperature phase favour a
Kosterlitz-Thouless-like (KT) singularity over a second-order phase transition.
Unconstrained KT fits of chi and xi confirm the predicted value for the
critical exponent nu, while the values of eta deviate from the theoretical
prediction. Additionally we apply finite-size scaling theory and investigate
the question of multiplicative logarithmic corrections to a KT transition. As
for the critical exponents our results are similar to data obtained from the XY
model, so that both models probably lie in the same universality class.Comment: 13 pages, Latex, 7 figures, to appear in Physica
Auto-WEKA 2.0: Automatic model selection and hyperparameter optimization in WEKA
Article / Letter to editorLeiden Inst Advanced Computer Science
Isospin Effects on Strangeness in Heavy-Ion Collisions
Kaon properties are studied within the framework of a fully covariant
transport approach. The kaon-nucleon potential is evaluated in two schemes, a
chiral perturbative approach and an effective One-Boson-Exchange model. Isospin
effects are explicitly accounted for in both models. The transport calculations
indicate a significant sensitivity of momentum distributions and total yields
of isospin states on the choice of the kaon-nucleon interaction.
Furthermore, isospin effects are rather moderate on absolute kaon yields, but
appear on strangeness ratios. This is an important issue in determining the
high density symmetry energy from studies of strangeness production in
heavy-ion collisions.Comment: 15 papes, 5 figures. Accepted for publication in Nuclear Physic
Viral Retinitis following Intraocular or Periocular Corticosteroid Administration: A Case Series and Comprehensive Review of the Literature.
Abstract Purpose: To describe viral retinitis following intravitreal and periocular corticosteroid administration. Methods: Retrospective case series and comprehensive literature review. Results: We analyzed 5 unreported and 25 previously published cases of viral retinitis following local corticosteroid administration. Causes of retinitis included 23 CMV (76.7%), 5 HSV (16.7%), and 1 each VZV and unspecified (3.3%). Two of 22 tested patients (9.1%) were HIV positive. Twenty-one of 30 (70.0%) cases followed one or more intravitreal injections of triamcinolone acetonide (TA), 4 (13.3%) after one or more posterior sub-Tenon injections of TA, 3 (10.0%) after placement of a 0.59-mg fluocinolone acetonide implant (Retisert), and 1 (3.3%) each after an anterior subconjunctival injection of TA (together with IVTA), an anterior chamber injection, and an anterior sub-Tenon injection. Mean time from most recent corticosteroid administration to development of retinitis was 4.2 months (median 3.8; range 0.25-13.0). Twelve patients (40.0%) had type II diabetes mellitus. Treatments used included systemic antiviral agents (26/30, 86.7%), intravitreal antiviral injections (20/30, 66.7%), and ganciclovir intravitreal implants (4/30, 13.3%). Conclusions: Viral retinitis may develop or reactivate following intraocular or periocular corticosteroid administration. Average time to development of retinitis was 4 months, and CMV was the most frequently observed agent. Diabetes was a frequent co-morbidity and several patients with uveitis who developed retinitis were also receiving systemic immunosuppressive therapy
Automatic construction of parallel portfolios via algorithm configuration
FWN – Publicaties zonder aanstelling Universiteit Leide
Butterflies (Lepidoptera) considered as threatened in Minas Gerais, Brazil
The twenty species of butterflies (diurnal Lepidoptera) considered as threatened in the Minas Gerais (by statute) are described and discussed in relation to distribution, appearance and known records.24125
Charge-density waves in one-dimensional Hubbard superlattices
We study the formation of charge density waves (CDW's) in one-dimensional
Hubbard superlattices, modeled by a repeated pattern of repulsive (U>0) and
free (U=0) sites. By means of Lanczos diagonalizations for the ground state, we
calculate the charge structure factor. Our results show that while the
superlattice structure affects the modulation of the charge density waves, the
periodicity can still be predicted through an effective density. We also show
that, for a fixed repulsive layer thickness, the periodicity of the CDW is an
oscillatory function of the free layer thickness.Comment: 4 pages, 4 figure
Auto-WEKA 2.0: Automatic model selection and hyperparameter optimization in WEKA
Algorithms and the Foundations of Software technolog
Fine Root Productivity and Dynamics on a Forested Floodplain in South Carolina
The highly dynamic, fine-root component of forested wetland ecosystems has received inadequate attention in the literature. Characterizing fine root dynamics is a challenging endeavor in any system, but the difficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (\u3c 3mm) biomass, production, and turnover were estimated for three soils exhibiting different drainage patterns within a mixed-oak community on the Coosawhatchie River floodplain, Jasper County, SC. Within a 45-cm deep vertical profile, 74% of total fine root biomass was restricted to the upper 15 cm of the soil surface. Fine root biomass decreased as the soil became less well-drained (e.g., fine root biomass in well-drained soil \u3e intermediately drained soil \u3e poorly drained soil). Fine root productivity was measured for one year using minirhizotrons and in-situ screens. Both methods suggested higher fine root production in better drained soils but showed frequent fluctuations in fine root growth and mortality, suggesting the need for frequent sampling at short intervals (e.g., monthly) to accurately assess fine root growth and turnover. Fine root production, estimated with in-situ screens, was 1.5, 1.8, and 0.9 Mg ha-1 yr-1 in the well-drained, intermediately drained, and poorly drained soils, respectively. Results from minirhizotrons indicated that fine roots in well-drained soils grew to greater depths while fine roots in poorly drained soils were restricted to surface soils. Minirhizotrons also revealed that the distribution of fine roots among morphological classes changed between well-drained and poorly drained soils
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