Quantitative phase-field modeling of solidification at high Lewis number

A phase-field model of nonisothermal solidification in dilute binary alloys is used to study the variation of growth velocity, dendrite tip radius, and radius selection parameter as a function of Lewis number at fixed undercooling. By the application of advanced numerical techniques, we have been able to extend the analysis to Lewis numbers of order 10 000, which are realistic for metals. A large variation in the radius selection parameter is found as the Lewis number is increased from 1 to 10 000

Digestibilidade aparente de nutrientes de dietas contendo farelo da castanha de caju (Anacardium occidentale L.) em caprinos

Foi avaliada a digestibilidade aparente dos nutrientes em dietas contendo farelo da castanha de caju (FCC) e feno de Tifton 85 em diferentes níveis de inclusão. Utilizaram-se doze caprinos com peso vivo inicial de 17,2 kg, distribuídos num delineamento inteiramente casualizado com quatro tratamentos e seis repetições no tempo. As inclusões de FCC nas dietas foram de 10; 15; 20 e 25% com base na matéria seca (MS). A estimativa da produção fecal foi avaliada por coleta total. A inclusão nas dietas de até 25% de FCC na MS promoveu o aumento (P<0,05) das digestibilidades aparente da proteína bruta e do extrato etéreo. As inclusões de FCC ocasionaram decréscimos lineares tanto na digestibilidade aparente da fibra em detergente neutro quanto da fibra em detergente ácido, nessas porções fibrosas foram encontrados decréscimos de 0,24 e 0,50 unidades percentuais das digestibilidades à cada 1% da inclusão do FCC, respectivamente

Lifetime of Wannier-Stark states in semiconductor superlattices under strong Zener tunneling to above-barrier bands

For high electric fields, the lifetime of Wannier-Stark ladder states in a periodic potential is reduced by the fundamental process of Zener tunneling. We report on the analysis of the coherence lifetime of such states in semiconductor superlattices by interband spectroscopy. The reduction of lifetime by strong coupling between bands can only in the first approximation be described by the well-known Zener theory. A recently developed theoretical model is applied to calculate directly the tunneling probability of Wannier-Stark states as a function of the electric field. The theoretical results compare well with experiment, reproducing the complex interplay of both nonresonant and resonant Zener tunneling to higher bands. By comparing experiment and theory for a superlattice with a symmetric and one with a nonsymmetric potential, we can draw conclusions on a very general basis about the sensitive dependence of Zener tunneling on the specific dispersion relation of the carriers

Evaluation of a novel mitochondrial Pan-Mucorales marker for the detection, identification, quantification, and growth stage determination of mucormycetes

Mucormycosis infections are infrequent yet aggressive and serious fungal infections. Early diagnosis of mucormycosis and its discrimination from other fungal infections is required for targeted treatment and more favorable patient outcomes. The majority of the molecular assays use 18 S rDNA. In the current study, we aimed to explore the potential of the mitochondrial rnl (encoding for large-subunit-ribosomal-RNA) gene as a novel molecular marker suitable for research and diagnostics. Rnl was evaluated as a marker for: (1) the Mucorales family, (2) species identification (Rhizopus arrhizus, R. microsporus, Mucor circinelloides, and Lichtheimia species complexes), (3) growth stage, and (4) quantification. Sensitivity, specificity, discriminatory power, the limit of detection (LoD), and cross-reactivity were evaluated. Assays were tested using pure cultures, spiked clinical samples, murine organs, and human paraffin-embedded-tissue (FFPE) samples. Mitochondrial markers were found to be superior to nuclear markers for degraded samples. Rnl outperformed the UMD universal® (Molyzm) marker in FFPE (71.5% positive samples versus 50%). Spiked blood samples highlighted the potential of rnl as a pan-Mucorales screening test. Fungal burden was reproducibly quantified in murine organs using standard curves. Identification of pure cultures gave a perfect (100%) correlation with the detected internal transcribed spacer (ITS) sequence. In conclusion, mitochondrial genes, such as rnl, provide an alternative to the nuclear 18 S rDNA genes and deserve further evaluation.CD laboratory: This research was funded by the Christian Doppler Laboratory for fungal infections

Field-induced delocalization and Zener breakdown in semiconductor superlattices

We investigate the energy spectrum and the electron dynamics of a band in a semiconductor superlattice as a function of the electric field. Linear optical spectroscopy shows that, for high fields, the well-known localization of the Bloch states is followed by a field-induced delocalization, associated with Zener breakdown. Using time-resolved measurements, we observe Bloch oscillations in a regime where they are damped by Zener breakdown

Towards a Three-Dimensional Phase-Field Model of Dendritic Solidification with Physically Realistic Interface Width

We review the application of advanced numerical techniques such as adaptive mesh refinement, implicit time stepping, multigrid solvers and massively parallel implementations as a route to obtaining solutions to the three-dimensional phase-field problem with a domain size and interface resolution previously possible only in two dimensions. Using such techniques it is shown that such models are tractable even as the interface width approaches the solute capillary length

The Interplay of Intraband and Interband Polarization in the Ultrafast Response of Biased Semiconductor Superlattices

We present the results of a new excitonic formalism for the treatment of ultrafast dynamics in asymmetric semiconductor multiple quantum well structures. The method is infinite order in the optical field, with truncation of the infinite hierarchy of dynamical equations being accomplished via a factorization of six-particle correlation functions into a product of two- and four-particle ones. We use this formalism to calculate the THz emission and degenerate four-wave mixing signals from biased semiconductor superlattices under different excitation conditions. We present a number of density-dependent effects that demonstrate the central role that the intraband polarization plays in determining and modifying the nonlinear ultrafast response of the system