The recent discovery of ferroelectricity in thin hafnium oxide films has led to a resurgence of interest in ferroelectric memory devices. Although both experimental and theoretical studies on this ...new ferroelectric system have been undertaken, much remains to be unveiled regarding its domain landscape and switching kinetics. Here we demonstrate that the switching of single domains can be directly observed in ultrascaled ferroelectric field effect transistors. Using models of ferroelectric domain nucleation we explain the time, field and temperature dependence of polarization reversal. A simple stochastic model is proposed as well, relating nucleation processes to the observed statistical switching behavior. Our results suggest novel opportunities for hafnium oxide based ferroelectrics in nonvolatile memory devices.
Comparisons of the material qualities of pressed, milled, and 3D-printed occlusal devices are sparse, complicating informed decisions on material choice.
The purpose of this in vitro study was to ...compare the material properties of pressed, milled, and 3D-printed resins, as well as how these are affected by thermal aging. These data were then used to estimate the likely clinical performance of the tested materials.
Three pressed (ProBase Cold; Ivoclar Vivadent AG, Palapress clear; Kulzer GmbH, Aesthetic Blue clear; Candulor), 3 milled (Temp Premium Flexible Transpa; Zirkonzahn, idodentine PMMA transparent; Unión Dental S.A., Yamahachi PMMA clear; Yamahachi Dental MFG), and three 3D-printed (Freeprint splint; DETAX GmbH, LuxaPrint Ortho Plus; DMG GmbH, Nextdent Ortho Clear; Vertex-Dental B.V.) resin materials were evaluated. Flexural strength, Martens hardness (HM), Vickers hardness (HV), water sorption, water solubility, and surface topography were analyzed. The tests were carried out after 50 hours of water storage at 37 °C (baseline) and after simulated aging (50 hours of water storage at 37 °C, followed by 20 000 thermocycles TC at 5 °C and 55 °C).
At baseline, the mean flexural strength values were 92.8 to 99.5 MPa for pressed, 95.1 to 122.0 MPa for milled, and 19.5 to 91.3 MPa for 3D-printed materials. After aging, these values were 87.6 to 93.5 MPa for pressed, 93.1 to 116.0 MPa for milled, and 13.0 to 63.3 MPa for 3D-printed resins. The mean HM values were 130.1 to 134.1 N/mm for pressed and 130.3 to 158.5 N/mm for milled resins. After aging, the mean HM ranged from 121.6 to 124.2 N/mm for pressed and 116.2 to 149.7 N/mm for milled resins. The mean HV values were 18.2 to 19.9 for pressed and 18.4 to 23.0 for milled resins before aging and 16.9 to 18.7 for pressed and 17.3 to 22.3 N/mm for milled resins after aging. Printed resins could not be measured. At baseline, the mean modulus of elasticity ranged from 4.6 to 4.8 GPa for pressed and from 4.7 to 5.3 GPa for milled resins. For 3D-printed resins, only 1 material could be measured (3.7 GPa). The mean sorption values were 8.6 to 9.2 μg/mm3 for pressed, 7.9 to 10.5 μg/mm3 for milled, and 9.2 to 21.2 μg/mm3 for additive resins. After aging, these values were 21.1 to 22.6 μg/mm3 for pressed, 20.5 to 23.7 μg/mm3 for milled, and 19.4 to 45.5 μg/mm3 for 3D-printed resins. The mean solubility values ranged from 0.3 to 1.4 μg/mm3 for pressed, 0.4 to 1.7 μg/mm3 for milled, and −3.5 to 11 μg/mm3 for 3D-printed materials.
Pressed and milled resins can be considered equivalent in terms of their material properties. Relative to the pressed and milled resins, the 3D-printed resins had lower flexural strength and hardness values and higher water sorption and solubility.
This book is a presentation of the basic concept of social, environmental and cultural connectivity in past societies, as embodied in a diversity of disciplines in the Cluster of Excellence ROOTS. ...Thus, rather pragmatically driven ideas of socio-environmental connectivities are described, which form the basis of the Cluster of Excellence in its research. A discussion of the fluidness of the term ‘connectivity’ and the applicability of the concept opens the arena for diverse interpretations. With various case and concept studies, the reader may advance into the perspectives that develop from the new interdisciplinary interaction. These include both rarely considered dependencies between nomadic and urban lifestyles, and aspects of water supply and water features, which represent an area of connectivity between the environment and agglomerated human settlement structures. Moreover, diachronic aspects are presented in various studies on the role of connectivities in the development of social inequality, the use of fortification or also waste behaviour, and the creation of linguistic features in written media. In sum, facets of connectivity research are revealed that are also being investigated in numerous other disciplines with further results in the Kiel Excellence Cluster ROOTS.
The transition metal oxides ZrO2 and HfO2 as well as their solid solution are widely researched and, like most binary oxides, are expected to exhibit centrosymmetric crystal structure and therewith ...linear dielectric characteristics. For this reason, those oxides, even though successfully introduced into microelectronics, were never considered to be more than simple dielectrics possessing limited functionality. Here we report the discovery of a field-driven ferroelectric phase transition in pure, sub 10 nm ZrO2 thin films and a composition- and temperature-dependent transition to a stable ferroelectric phase in the HfO2–ZrO2 mixed oxide. These unusual findings are attributed to a size-driven tetragonal to orthorhombic phase transition that in thin films, similar to the anticipated tetragonal to monoclinic transition, is lowered to room temperature. A structural investigation revealed the orthorhombic phase to be of space group Pbc21, whose noncentrosymmetric nature is deemed responsible for the spontaneous polarization in this novel, nanoscale ferroelectrics.
Based on an ethnographic study in a German prison, this article explores the question of what meaning incarcerated men attach to sport in light of the loss of freedom and autonomy which according to ...Sykes are particular ‘pains of imprisonment’. The material shows the following: (1) Incarceration is perceived by imprisoned men as a life under duress and proves to be a stark contrast to life outside prison due to the limited freedom of movement, action and decision making. (2) Sport is a means for incarcerated men to bring back memories of being free and to mentally escape into the time before imprisonment. (3) Sport is one of the few opportunities for imprisoned men to spend time in fresh air, which results in a physically–sensually experienced liberation. (4) Participation in sports enables the incarcerated to temporarily regain freedom of action and decision making. Overall, the findings indicate that sport can best be understood as a help in coping with incarceration. It is concluded from the findings that imprisoned men attach their own meanings to sport, largely detached from the function of sport ascribed by the institution (such as rehabilitation and health promotion).
This paper deals with the analysis of long-term changes in population densities at the regional and macro-regional scale and in the density of metapopulations. The following issues concerning ...estimations are addressed: chronological resolution of demographic changes, estimation of the weight of values for population density in order to transform the initial values included in the sample into the values that may be compared with each other at the regional scale, calibration of the transformed values into real population densities, and the estimation of the weight of values for population density at the scales of macro-regions and for the density of metapopulations. The proposed methods are tested on demographic changes in Central Europe, Southern Scandinavia, Southeastern Europe, and the Near East. The obtained results represent major trends in demographic development, while the proposed methodology could also be applied in other wide-scale demographic analyses.
This article examines early antiterrorism negotiations within international organisations (IOs) and their outcomes. It assesses how international cooperation emerged in specialised, regional, and ...global IOs and provides a long-term overview from the 1960s until the late 1980s. Drawing on primary sources and scholarly literature, this article identifies the patterns, trends, and key characteristics of the successfully adopted measures. It demonstrates that early multilateral antiterrorism efforts faced several obstacles (sovereignty, national interests, mistrust, and geopolitics), and, therefore, international negotiations fared better when following a piecemeal approach within specialised or regional organisations, where the focus could be on specific aspects of terrorism (e.g., hostage-takings). A key characteristic of the successfully adopted antiterrorism instruments was the aut dedere aut iudicare principle, which allowed states to maintain perceptions of sovereignty by either extraditing or trying a suspect. The antiterrorism efforts examined here were mostly preventative in design and worked to discourage future terrorists by ensuring that safe havens were closed and that perpetrators faced justice. The shift to suicide terrorism in the 1990s would instead require new international antiterrorism efforts to focus on pre-emptive strategies, depriving terrorists of the means to carry out attacks. The roots of these measures were laid in the 1980s.
PDF
