Holographic analysis of diffraction structure factors

We combine the theory of inside-source/inside-detector x-ray fluorescence holography and Kossel lines/x ray standing waves in kinematic approximation to directly obtain the phases of the diffraction structure factors. The influence of Kossel lines and standing waves on holography is also discussed. We obtain partial phase determination from experimental data obtaining the sign of the real part of the structure factor for several reciprocal lattice vectors of a vanadium crystal.Comment: 4 pages, 3 figures, submitte

Phase-field crystal modelling of crystal nucleation, heteroepitaxy and patterning

We apply a simple dynamical density functional theory, the phase-field-crystal (PFC) model, to describe homogeneous and heterogeneous crystal nucleation in 2d monodisperse colloidal systems and crystal nucleation in highly compressed Fe liquid. External periodic potentials are used to approximate inert crystalline substrates in addressing heterogeneous nucleation. In agreement with experiments in 2d colloids, the PFC model predicts that in 2d supersaturated liquids, crystalline freezing starts with homogeneous crystal nucleation without the occurrence of the hexatic phase. At extreme supersaturations crystal nucleation happens after the appearance of an amorphous precursor phase both in 2d and 3d. We demonstrate that contrary to expectations based on the classical nucleation theory, corners are not necessarily favourable places for crystal nucleation. Finally, we show that adding external potential terms to the free energy, the PFC theory can be used to model colloid patterning experiments.Comment: 21 pages, 16 figure

Phase-field approach to polycrystalline solidification including heterogeneous and homogeneous nucleation

Advanced phase-field techniques have been applied to address various aspects of polycrystalline solidification including different modes of crystal nucleation. The height of the nucleation barrier has been determined by solving the appropriate Euler-Lagrange equations. The examples shown include the comparison of various models of homogeneous crystal nucleation with atomistic simulations for the single component hard-sphere fluid. Extending previous work for pure systems (Gránásy L, Pusztai T, Saylor D and Warren J A 2007 Phys. Rev. Lett. 98 art no 035703), heterogeneous nucleation in unary and binary systems is described via introducing boundary conditions that realize the desired contact angle. A quaternion representation of crystallographic orientation of the individual particles (outlined in Pusztai T, Bortel G and Gránásy L 2005 Europhys. Lett. 71 131) has been applied for modeling a broad variety of polycrystalline structures including crystal sheaves, spherulites and those built of crystals with dendritic, cubic, rhombododecahedral, truncated octahedral growth morphologies. Finally, we present illustrative results for dendritic polycrystalline solidification obtained using an atomistic phase-field model

Inflammation and oxidative stress caused by nitric oxide synthase uncoupling might lead to left ventricular diastolic and systolic dysfunction in patients with hypertension

Objective: To investigate the role of oxidative stress, inflammation, hypercoagulability and neuroendocrine activation in the transition of hypertensive heart disease to heart failure with preserved ejection fraction (HFPEF). Methods: We performed echocardiography for 112 patients (≥ 60 years old) with normal EF (18 controls and 94 with hypertension), and determined protein carbonylation (PC), and tetrahydrobiopterin (BH4), C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), fibrinogen, plasminogen activator inhibitor type-I (PAI-I), von Willebrand factor, chromogranin A (cGA) and B-type natriuretic peptide (BNP) levels from their blood samples. Results: We found that 40% (38/94) of the patients with hypertension (HT) had no diastolic dysfunction (HTDD-), and 60% (56/94) had diastolic dysfunction (HTDD+). Compared to the controls, both patient groups had increased PC and BH4, TNF-α, PAI-I and BNP levels, while the HTDD+ group had elevated cGA and CRP levels. Decreased atrial and longitudinal left ventricular (LV) systolic and diastolic myocardial deformation (strain and strain rate) was demonstrated in both patient groups versus the control. Patients whose LV diastolic function deteriorated during the follow-up had elevated PC and IL-6 level compared to their own baseline values, and to the respective values of patients whose LV diastolic function remained unchanged. Oxidative stress, inflammation, BNP and PAI-I levels inversely correlated with LV systolic, diastolic and atrial function. Conclusions: In patients with HT and normal EF, the most common HFPEF precursor condition, oxidative stress and inflammation may be responsible for LV systolic, diastolic and atrial dysfunction, which are important determinants of the transition of HT to HFPEF

Parallel Evolution under Chemotherapy Pressure in 29 Breast Cancer Cell Lines Results in Dissimilar Mechanisms of Resistance

Background: Developing chemotherapy resistant cell lines can help to identify markers of resistance. Instead of using a panel of highly heterogeneous cell lines, we assumed that truly robust and convergent pattern of resistance can be identified in multiple parallel engineered derivatives of only a few parental cell lines. Methods: Parallel cell populations were initiated for two breast cancer cell lines (MDA-MB-231 and MCF-7) and these were treated independently for 18 months with doxorubicin or paclitaxel. IC50 values against 4 chemotherapy agents were determined to measure cross-resistance. Chromosomal instability and karyotypic changes were determined by cytogenetics. TaqMan RT-PCR measurements were performed for resistance-candidate genes. Pgp activity was measured by FACS. Results: All together 16 doxorubicin- and 13 paclitaxel-treated cell lines were developed showing 2-46 fold and 3-28 fold increase in resistance, respectively. The RT-PCR and FACS analyses confirmed changes in tubulin isofom composition, TOP2A and MVP expression and activity of transport pumps (ABCB1, ABCG2). Cytogenetics showed less chromosomes but more structural aberrations in the resistant cells. Conclusion: We surpassed previous studies by parallel developing a massive number of cell lines to investigate chemoresistance. While the heterogeneity caused evolution of multiple resistant clones with different resistance characteristics, the activation of only a few mechanisms were sufficient in one cell line to achieve resistance. © 2012 Tegze et al

Phase-field modeling of eutectic structures on the nanoscale: the effect of anisotropy

This is a post-peer-review, pre-copyedit version of an article published in Journal of Materials Science. The final authenticated version is available online at: https://doi.org/10.1007/s10853-017-0853-8A simple phase-field model is used to address anisotropic eutectic freezing on the nanoscale in two (2D) and three dimensions (3D). Comparing parameter-free simulations with experiments, it is demonstrated that the employed model can be made quantitative for Ag-Cu. Next, we explore the effect of material properties, and the conditions of freezing on the eutectic pattern. We find that the anisotropies of kinetic coefficient and the interfacial free energies (solid-liquid and solid-solid), the crystal misorientation relative to pulling, the lateral temperature gradient, play essential roles in determining the eutectic pattern. Finally, we explore eutectic morphologies, which form when one of the solid phases are faceted, and investigate cases, in which the kinetic anisotropy for the two solid phases are drastically different

Phase-Field Modeling of Biomineralization in Mollusks and Corals: Microstructure vs Formation Mechanism

[Image: see text] While biological crystallization processes have been studied on the microscale extensively, there is a general lack of models addressing the mesoscale aspects of such phenomena. In this work, we investigate whether the phase-field theory developed in materials’ science for describing complex polycrystalline structures on the mesoscale can be meaningfully adapted to model crystallization in biological systems. We demonstrate the abilities of the phase-field technique by modeling a range of microstructures observed in mollusk shells and coral skeletons, including granular, prismatic, sheet/columnar nacre, and sprinkled spherulitic structures. We also compare two possible micromechanisms of calcification: the classical route, via ion-by-ion addition from a fluid state, and a nonclassical route, crystallization of an amorphous precursor deposited at the solidification front. We show that with an appropriate choice of the model parameters, microstructures similar to those found in biomineralized systems can be obtained along both routes, though the time-scale of the nonclassical route appears to be more realistic. The resemblance of the simulated and natural biominerals suggests that, underneath the immense biological complexity observed in living organisms, the underlying design principles for biological structures may be understood with simple math and simulated by phase-field theory