Search results for "heterogeneous"

Seed- and wall-induced heterogeneous nucleation in charged colloidal model systems under microgravity

2011

Understanding the process that drives an undercooled fluid to the crystal state is still a challenging issue for condensed matter physics and plays a key role in designing new materials. The crystallization kinetics and the resulting polycrystalline morphology are given by a complex interplay of crystal nucleation, growth, and ripening. A great deal of progress has been made in recent years using colloidal suspensions as model systems in the study of crystallization. Close analogies to atomic systems are observed which can be exploited to address questions not accessible in atomic solidification. Here we present systematic measurements of the crystallization kinetics of a charged colloidal …

Tuning Selectivities in Gas Separation Membranes Based on Polymer-Grafted Nanoparticles

2020

Polymer membranes are critical to many sustainability applications that require the size-based separation of gas mixtures. Despite their ubiquity, there is a continuing need to selectively affect the transport of different mixture components while enhancing mechanical strength and hindering aging. Polymer-grafted nanoparticles (GNPs) have recently been explored in the context of gas separations. Membranes made from pure GNPs have higher gas permeability and lower selectivity relative to the neat polymer because they have increased mean free volume. Going beyond this ability to manipulate the mean free volume by grafting chains to a nanoparticle, the conceptual advance of the present work is…

(Ag)Pd-Fe3O4 Nanocomposites as Novel Catalysts for Methane Partial Oxidation at Low Temperature

2020

Nanostructured composite materials based on noble mono-(Pd) or bi-metallic (Ag/Pd) particles supported on mixed iron oxides (II/III) with bulk magnetite structure (Fe3O4) have been developed in order to assess their potential for heterogeneous catalysis applications in methane partial oxidation. Advancing the direct transformation of methane into value-added chemicals is consensually accepted as the key to ensuring sustainable development in the forthcoming future. On the one hand, nanosized Fe3O4 particles with spherical morphology were synthesized by an aqueous-based reflux method employing different Fe (II)/Fe (III) molar ratios (2 or 4) and reflux temperatures (80, 95 or 110 &deg

Monotonic solution of flow and transport problems in heterogeneous media using Delaunay unstructured triangular meshes

2013

Transport problems occurring in porous media and including convection, diffusion and chemical reactions, can be well represented by systems of Partial Differential Equations. In this paper, a numerical procedure is proposed for the fast and robust solution of flow and transport problems in 2D heterogeneous saturated media. The governing equations are spatially discretized with unstructured triangular meshes that must satisfy the Delaunay condition. The solution of the flow problem is split from the solution of the transport problem and it is obtained with an approach similar to the Mixed Hybrid Finite Elements method, that always guarantees the M-property of the resulting linear system. The…

The Heterogeneous Fleet Vehicle Routing Problem with Draft Limits

2023

Over the past two decades, international maritime transport has been characterized by the advent of ever larger ships. This phenomenon is known as naval gigantism. If, on the one hand, naval gigantism allows to reduce transport costs by exploiting the economies of scale achievable by large ships, on the other hand, it implies a series of operational issues. Indeed, due to their large draft, such giant vessels are not allowed to enter small ports when fully or near-fully loaded, and in some cases, they cannot enter such small ports at all. In fact, their draft can strongly vary depending on the load on board. This implies restrictions for vessels in accessing ports, which impact not only at …

Heterogeneous structures studied by an interphase elasto-plastic damaging model

2013

Heterogeneous materials present a mechanical response strongly dependent on the static and kinematic phenomena occurring in the constituents and at their joints. At the mesoscopic level the interaction between the units is simulated by mean of apposite mechanical devices such as the zero thickness interface model where contact tractions and displacement discontinuities are the primary static and kinematic variables respectively. In heterogeneous materials the response also depends on joint internal stresses. The introduction of internal stresses brings to the interphase model or an enhancement of the classical zero-thickness interface. With the term 'interphase' we shall mean a layer separa…

A Multilevel Analysis of Economic Literacy Among International Students

2021

International student mobility has increased in the past years. The inclusion of a highly heterogeneous group of students requires updated recruitment and admission strategies. A particularly vulnerable group of international students are refugees, who have an exceptionally high risk of dropping out of their studies. We present an entrance assessment of incoming international students from 77 countries who are at the beginning of their studies in Germany. Based on this unique sample, we examine (i) whether there are systematic country-specific effects on the economic literacy of beginning students of business and economics and (ii) whether refugee students differ from the group of internati…

Expression of selected molecular factors in two types of endometrial cancer

2021

BACKGROUND Endometrial cancers (EC) are a heterogeneous group of malignant neoplasms differing in etiology, clinical-pathological features and prognosis. OBJECTIVES To determine the differences between the expression of selected molecular factors and find connections between them in order to isolate possible biomarkers influencing treatment options. MATERIAL AND METHODS The investigated data involved archival histological preparations obtained from uterine EC samples taken from 137 patients, treated surgically between 2007 and 2014. The immunohistochemical Dako EnVisionTM Flex+ method was applied. RESULTS The expression of ERβ, MLH1 and BRCA1 was lower in ECI than in ECII patients. The ERα …

Photocatalytic membrane reactors

2008

A comparison of HONO budgets for two measurement heights at a field station within the boreal forest in Finland

2015

Atmospheric concentrations of nitrous acid (HONO), one of the major precursors of the hydroxyl radical (OH) in the troposphere, significantly exceed the values predicted by the assumption of a photostationary state (PSS) during daytime. Therefore, additional sources of HONO were intensively investigated in the last decades. This study presents budget calculations of HONO based on simultaneous measurements of all relevant species, including HONO and OH at two different measurement heights, i.e. 1 m above the ground and about 2 to 3 m above the canopy (24 m above the ground), conducted in a boreal forest environment. We observed mean HONO concentrations of about 6.5 × 108 molecules cm−3 (26 p…