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An efficient algorithm and a data structure for computing and representing the aspect graph of polyhedral objects under orthographic projection are presented. The aspect graph is an approach to representing 3-D objects by a set of 2-D views, for the purpose of object recognition. In this approach the viewpoint space is partitioned into regions such that in each region the qualitative structure of the line drawing does not change. The viewing data of an object is the partition of the viewpoint space together with a representative view in each region. The algorithm computes the viewing data for line drawings of polyhedral objects under orthographic projection.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
High-entropy alloys (HEAs) are an emerging class of advanced structural alloys under extensive research; yet, the properties of the liquid states of these materials, which are relevant to their processing, have been far less explored. In this work, we utilize ab initio molecular dynamics simulations to investigate the melt properties of a representative HEA—the Cantor alloy—and its derivatives: CrMnFeCoNi, CrFeCoNi, and CrCoNi. The atomic dynamics of these melts at various temperatures are investigated, specifically to analyze their electronic and atomic structures, including charge transfer, pair distribution functions, and short-range order. Results are compared with existing information for the liquids of metallic glasses, which also typically contain multiple principal elements, but retain the amorphous state under moderate to fast cooling rates. The present results provide insights into the structural and bonding factors favoring solidification to single-phase solid solutions in HEAs.
A daily occurrence in the life of a plant is the function of a photosystem II (PSII) damage and repair cycle in chloroplasts. This unique phenomenon involves the frequent turnover of D1, the 32-kDa reaction-center protein of PSII (chloroplast psbA gene product). In the model organism Dunaliella salina (a green alga), growth under low light (100 mol of photons per m2 per sec) entails damage, degradation, and replacement of D1 every 7 hr. Growth under irradiance stress (2200 micromol of photons per m2 per sec) entails damage to D1 every 20 min. The rate of de novo D1 biosynthesis under conditions of both low light and irradiance stress was found to be fairly constant on a per chloroplast or cell basis. The response of D. salina to the enhanced rate of damage entails an accumulation of photodamaged centers (80% of all PSII) and the formation of thylakoid membranes containing a smaller quantity of photosystem I (PSI) centers (about 10% of that in cells grown under low light). These changes contribute to a shift in the PSII/PSI ratio from 1.4:1 under low-light conditions to 15:1 under irradiance stress. The accumulation of photodamaged PSII under irradiance stress reflects a chloroplast inability to match the rate of D1 degradation or turnover with the rate of damage for individual PSII complexes. The altered thylakoid membrane organization ensures that a small fraction of PSII centers remains functional under irradiance stress and sustains electron flow from H2O to ferredoxin with rates sufficient for chloroplast photosynthesis and cell growth.
This paper contemplates ambitious reforms of the international financial architecture. It proposes routinising the expansion of IMF quotas and the conduct of exchange rate surveillance. It contemplates an expanded role for the SDR in international transactions, which would require someone — like the IMF — to act as market maker. It considers proposals for reimposing Glass–Steagall-like restrictions on commercial and investment banking, something that will have to be coordinated internationally to be feasible. All this of course presupposes meaningful IMF governance reform so that the institution has the legitimacy and efficiency to assume these additional responsibilities.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The problem of plastic spin is phrased in terms of a notion of mechanical equivalence among local intermediate configurations of an elastic/ plastic crystalline solid. This idea is used to show that, without further qualification, the plastic spin may be suppressed at the constitutive level. However, the spin is closely tied to an underlying undistorted crystal lattice which, once specified, eliminates the freedom afforded by mechanical equivalence. As a practical matter a constitutive specification of plastic spin is therefore required. Suppression of plastic spin thus emerges as merely one such specification among many. Restrictions on these are derived in the case of rate-independent response.
In the present work explicit formulas for analyzing the birth of limit cycles arising in the Chua's circuit through a Hopf bifurcation is provided. A local amplitude equation is derived using a frequency domain approach and harmonic balance approximations. Furthermore, the first Lyapunov index used to detect degenerate Hopf bifurcations is derived in terms of the parameters of the nonlinear circuit. A perspective for analyzing other bifurcations using this frequency domain approach is discussed.
Abstract Die Ursprünge der aktivitätsbasierten Sensorik (ABS) liegen in der supramolekularen Chemie und der Entwicklung selektiver chemischer Rezeptoren nach dem Schlüssel‐Schloss‐Prinzip. In kurzer Zeit hat sich daraus ein eigenes Forschungsgebiet entwickelt, in dem die Synthese und Regulierung chemischer Moleküle zur Vermittlung biologischer Signal‐ und Stresskaskaden – insbesondere Metallionen und niedermolekulare Substanzen – untersucht werden. In chemischen Reaktionen wird die unterschiedliche Reaktivität biologischer Moleküle genutzt, um mit selektiven und empfindlichen Synthesemethoden ihre Rolle in komplexen lebenden Systemen aufzuklären. Die große Anwendungsbreite dieses reaktionsgetriebenen Ansatzes erleichtert den Einsatz auf Plattformen für die Bildgebung, von Fluoreszenz und Lumineszenz über Photoakustik und Magnetresonanz bis zur PET. Der Einsatz von ABS‐Methoden wird auch auf weitere Felder ausgeweitet, z. B. für die Suche nach Wirkstoffen und Materialien.
Este artigo amplia o diagnóstico de Tom Slater sobre as causas da gentrificação da pesquisa recente sobre gentrificação. Ele argumenta que o deslocamento de denúncia para celebração da gentrificação, a elisão do deslocamento dos residentes estabelecidos e o foco eufemístico em "mesclagem social" participam de um padrão de invisibilidade da classe operária na esfera pública e na investigação social. Essa obliteração do proletariado na cidade é reforçada pela heteronomia crescente da pesquisa urbana, na medida em que ela se torna mais ligada estreitamente aos interesses dos governantes da cidade. Ambas as tendências revelam e incitam a transformação do papel do Estado, de provedor de assistência social para populações de renda mais baixa para o de fornecedor de serviços e amenidades empresariais para urbanitas de classe média e alta , entre os quais a limpeza, no ambiente construído e nas ruas, dos detritos físicos e humanos engendrados pela desregulação econômica e o corte de gastos de previdência social. Para construir melhores modelos do nexo em transformação entre classe e espaço na cidade neoliberal, precisamos ressituar a gentrificação numa perspectiva mais ampla, revisando a análise de classe para capturar a (de)formação do proletariado pós-industrial, resistindo às seduções das problemáticas pré-fabricadas das ações políticas e dando destaque ao Estado como produtor da desigualdade socioespacial.
This paper presents a rigorous and comprehensive nonlinear circuit-theoretic foundation for the memristive Hodgkin–Huxley Axon Circuit model. We show that the Hodgkin–Huxley Axon comprises a potassium ion-channel memristor and a sodium ion-channel memristor, along with some mundane circuit elements. From this new perspective, many hitherto unresolved anomalous phenomena and paradoxes reported in the literature are explained and clarified. The yet unknown nonlinear dynamical mechanisms which give birth to the action potentials remain hidden within the memristors, and the race is on for uncovering the ultimate truth.
