Study on Crystallization Behavior of Polypropylene Induced by Nucleating Agent

The melting and recrystallization behavior of -iPP crystal induced by β -nucleating agent was studied. A new type of α-modification has been developed by self-seeding process. The growth process of these crystals is just like “photographic development process.” Crystalline phase transformation and the memory effect caused by local order was observed during the melting and annealing process. A high temperature is sufficient to destroy the local order and the β-nucleating agent efficiently induces formation of β-form.

Intrinsic nanostructure induced ultralow thermal conductivity yields enhanced thermoelectric performance in Zintl phase Eu2ZnSb2

The Zintl thermoelectric phase Eu2ZnSb2 has a remarkable combination of high mobility and low thermal conductivity that leads to good thermoelectric performance. The key feature of this compound is a crystal structure that has a Zn-site with a 50% occupancy. Here we use comparison of experimental thermal conductivity measurements and first principles thermal conductivity calculations to characterize the thermal conductivity reduction. We find that partial ordering, characterized by local order, but Zn-site disorder on longer scales, leads to an intrinsic nanostructuring induced reduction in thermal conductivity, while retaining electron mobility. This provides a direction for identifying Zintl compounds with ultralow lattice thermal conductivity and good electrical conductivity.

Adhesion Percolation Determines Global Deformation Behavior in Biomimetic Emulsions

Characterizing the mechanical properties of tissues is key for the understanding of fundamental biological processes such as morphogenesis or tumor progression. In particular, the intercellular adhesion forces, mediated by transmembrane proteins like cadherins, are expected to control the topology and viscoelastic behavior of tissues under mechanical stress. In order to understand the influence of adhesion in tissues, we use biomimetic emulsions in which droplets mimic cells and adhere to each other through specific bonds. Here, we tune both the binding energy of the adhesive inter-droplets contacts as well as the fraction of contacts that are adhesive, thereby defining a so-called adhesiveness. Our experimental results show that adhesion prevents the emergence of local order in emulsions even at high packing fractions by preventing energetically costly droplet rearrangements. By studying the deformation of droplets within packings with different average adhesiveness values, we reveal the existence of a threshold value of adhesiveness above which all droplets in a packing are deformed as adhesive ones irrespective of their local adhesive properties. We show that this critical adhesiveness coincides with the threshold for percolation of adhesive structures throughout the tissue. From a biological point of view, this indicates that only a fraction of adhesive cells would be sufficient to tune the global mechanical properties of a tissue, which would be critical during processes such as morphogenesis.

A Plane-Dependent Model of 3D Grid Cells for Representing Both 2D and 3D Spaces Under Various Navigation Modes

Grid cells are crucial in path integration and representation of the external world. The spikes of grid cells spatially form clusters called grid fields, which encode important information about allocentric positions. To decode the information, studying the spatial structures of grid fields is a key task for both experimenters and theorists. Experiments reveal that grid fields form hexagonal lattice during planar navigation, and are anisotropic beyond planar navigation. During volumetric navigation, they lose global order but possess local order. How grid cells form different field structures behind these different navigation modes remains an open theoretical question. However, to date, few models connect to the latest discoveries and explain the formation of various grid field structures. To fill in this gap, we propose an interpretive plane-dependent model of three-dimensional (3D) grid cells for representing both two-dimensional (2D) and 3D space. The model first evaluates motion with respect to planes, such as the planes animals stand on and the tangent planes of the motion manifold. Projection of the motion onto the planes leads to anisotropy, and error in the perception of planes degrades grid field regularity. A training-free recurrent neural network (RNN) then maps the processed motion information to grid fields. We verify that our model can generate regular and anisotropic grid fields, as well as grid fields with merely local order; our model is also compatible with mode switching. Furthermore, simulations predict that the degradation of grid field regularity is inversely proportional to the interval between two consecutive perceptions of planes. In conclusion, our model is one of the few pioneers that address grid field structures in a general case. Compared to the other pioneer models, our theory argues that the anisotropy and loss of global order result from the uncertain perception of planes rather than insufficient training.

Mean-field model of melting in superheated crystals based on a single experimentally measurable order parameter

Melting is one of the most studied phase transitions important for atomic, molecular, colloidal, and protein systems. However, there is currently no microscopic experimentally accessible criteria that can be used to reliably track a system evolution across the transition, while providing insights into melting nucleation and melting front evolution. To address this, we developed a theoretical mean-field framework with the normalised mean-square displacement between particles in neighbouring Voronoi cells serving as the local order parameter, measurable experimentally. We tested the framework in a number of colloidal and in silico particle-resolved experiments against systems with significantly different (Brownian and Newtonian) dynamic regimes and found that it provides excellent description of system evolution across melting point. This new approach suggests a broad scope for application in diverse areas of science from materials through to biology and beyond. Consequently, the results of this work provide a new guidance for nucleation theory of melting and are of broad interest in condensed matter, chemical physics, physical chemistry, materials science, and soft matter.

The Concept of Positive Law and Its Relationship to Religion and Morality

Can the concept of law be extended to other times and places in which the concept as understood in most countries and societies today—as a system of norms centred on a nation state, based on a constitution, formulated through codified legislation and judicial precedents, administered by lawmakers for its inception and judges for its implementation—simply did not exist? My contention is that such an extension is, at best, useless and, at worst, misleading. Producing an intelligible jurisprudence of the concept of law means keeping it within the reasonable boundaries of what is ordinarily understood by both lay and professional people when practising ‘the’ law. Developing a socio-historical jurisprudence of law, as distinct from other normativities, entails a threefold analysis: conceptual, historical, and praxiological. Following the ground broken by analytical philosopher Ludwig Wittgenstein, conceptual analysis engages in the exposition of the grammar through which concepts acquire their signification and are meaningfully used. In a manner inspired by philosopher of science Ian Hacking and by historian Reinhart Koselleck, historical analysis emphasizes the description of the birth, development, and use of concepts. Drawing on the work of sociologist Harold Garfinkel, praxiological analysis describes the practical methods used by people to make sense of their environment, to produce their local order, and to act accordingly. The three approaches converge in their insistence on adopting the endogenous/indigenous perspective towards social life and its production.