Electrical valley filtering in transition metal dichalcogenides

This work investigates the feasibility of electrical valley filtering for holes in transition metal dichalcogenides. We look specifically into the scheme that utilizes a potential barrier to produce valley-dependent tunneling rates, and perform the study with both a k.p based analytic method and a recursive Green's function based numerical method. The study yields the transmission coefficient as a function of incident energy and transverse wave vector, for holes going through lateral quantum barriers oriented in either armchair or zigzag directions, in both homogeneous and heterogeneous systems. The main findings are the following: 1) the tunneling current valley polarization increases with increasing barrier width or height, 2) both the valley-orbit interaction and band structure warping contribute to valley-dependent tunneling, with the former contribution being manifest in structures with asymmetric potential barriers, and the latter being orientation-dependent and reaching maximum for transmission in the armchair direction, and 3) for transmission ~ 0.1, a tunneling current valley polarization of the order of 10% can be achieved.Comment: 12 pages, 8 figure

A Condition-Based Deterioration Model for the Stochastic Dependency of Corrosion Rate and Crack Propagation in Corroded Concrete Structures

Physics-based models are intensively studied in mechanical and civil engineering but their constant increase in complexity makes them harder to use in a maintenance context, especially when degradation model can/should be updated from new inspection data. On the other hand, Markovian cumulative damage approaches such as Gamma processes seem promising; however, they suffer from lack of acceptability by the civil engineering community due to poor physics considerations. In this article, we want to promote an approach for modeling the degradation of structures and infrastructures for maintenance purposes which can be seen as an intermediate approach between physical models and probabilistic models. A new statistical, data-driven state-dependent model is proposed. The construction of the degradation model will be discussed within an application to the cracking of concrete due to chloride-induced corrosion. Numerical experiments will later be conducted to identify preliminary properties of the model in terms of statistical inferences. An estimation algorithm is proposed to estimate the parameters of the model in cases where databases suffer from irregularities

A risk-oriented degradation model for maintenance of reinforced concrete structure subjected to cracking

This article is within the context of decision models aimed for maintenance of structures and infrastructures in civil engineering. The contribution relies on the construction of a degradation model oriented toward risk analysis. The proposed model can be defined as a meta-model in the sense that it is based on observations while incorporating key features from the degradation process necessary for the maintenance decision. We propose to stimulate the construction of the degradation model based on the crack propagation of a submerged reinforced concrete structure subject to chloride-induced corrosion. Furthermore, a set of numerical illustrations is performed to demonstrate the advantages and applicability of the proposed approach in risk management and maintenance contexts

Méthode X-SFEM pour le calcul de structure à géométrie aléatoire : application au calcul d'un joint de soudure

In structural analysis, stochastic finite element methods offer a robust tool to deal with randomness on material properties or loadings. Unfortunately, there is still no available efficient strategy to deal with uncertainties on the geometry. Here, we bring an answer to this problem by proposing a new method based on an extension to the stochastic framework of the eXtended Finite Element Method (X-FEM). This method lies on the use of the level set technique for the implicit description of the random geometry and the use of Galerkin approximation at deterministic and stochastic levels. Here, this method is applied to the analysis of a random welded joint

NOA1 Functions in a Temperature-Dependent Manner to Regulate Chlorophyll Biosynthesis and Rubisco Formation in Rice

NITRIC OXIDE-ASSOCIATED1 (NOA1) encodes a circularly permuted GTPase (cGTPase) known to be essential for ribosome assembly in plants. While the reduced chlorophyll and Rubisco phenotypes were formerly noticed in both NOA1-supressed rice and Arabidopsis, a detailed insight is still necessary. In this study, by using RNAi transgenic rice, we further demonstrate that NOA1 functions in a temperature-dependent manner to regulate chlorophyll and Rubisco levels. When plants were grown at 30°C, the chlorophyll and Rubisco levels in OsNOA1-silenced plants were only slightly lower than those in WT. However, at 22°C, the silenced plants accumulated far less chlorophyll and Rubisco than WT. It was further revealed that the regulation of chlorophyll and Rubisco occurs at the anabolic level. Etiolated WT seedlings restored chlorophyll and Rubisco accumulations readily once returned to light, at either 30°C or 15°C. Etiolated OsNOA1-silenced plants accumulated chlorophyll and Rubisco to normal levels only at 30°C, and lost this ability at low temperature. On the other hand, de-etiolated OsNOA1-silenced seedlings maintained similar levels of chlorophyll and Rubisco as WT, even after being shifted to 15°C for various times. Further expression analyses identified several candidate genes, including OsPorA (NADPH: protochlorophyllide oxidoreductase A), OsrbcL (Rubisco large subunit), OsRALyase (Ribosomal RNA apurinic site specific lyase) and OsPuf4 (RNA-binding protein of the Puf family), which may be involved in OsNOA1-regulated chlorophyll biosynthesis and Rubisco formation. Overall, our results suggest OsNOA1 functions in a temperature-dependent manner to regulate chlorophyll biosynthesis, Rubisco formation and plastid development in rice

PHOTOREDUCTION OF PROTOCHLOROPHYLLIDE TO CHLOROPHYLLIDE IN 2-D-OLD DARK-GROWN BEAN (PHASEOLUS-VULGARIS CV COMMODORE) LEAVES - COMPARISON WITH 10-D-OLD DARK-GROWN (ETIOLATED) LEAVES

Two-d-old leaves which do not contain prolamellar bodies synthesize active protochlorophyllide in darkness. When protochlorophyllide is photoreduced by one intense white flash, a main chlorophyllide species emitting at 690 nm is formed. After the photoreduction, the emission maximum is shifted to 675 nm within 5 s. This result suggests that in young leaves, chlorophyllide formed after one flash is quickly released from the active site of NADPH: protochlorophyllide oxidoreductase. This interpretation is strenghtened by time-resolved fluorescence measurements at room temperature, showing that 675 nm emitting chlorophyllide does not transfer excitation energy to the 696 nm emitting chlorophyllide which is formed in very low amount. In 10-d-old bean leaves, the 690 nm chlorophyllide emitting species formed after one short flash undergoes the well-known rapid and Shibata spectral shifts. The 675 nm emitting chlorophyllide appears only as a shoulder. At both ages, the fluorescence intensity of the active protochlorophyllide strongly decreases during and after photoreduction, suggesting rapid modifications in the close environment of the pigment