A time domain model for the study of high frequency 3D wheelset–track interaction with non-Hertzian contact

A novel numerical model for train-track interaction is proposed in this paper to deal with wheel–rail interface dynamics in high frequency range. The complete model consists a 3D rotating flexible wheelset model, a 3D track model considering the discrete support of the rail and a non-linear, non-Hertzian model of wheel–rail contact. The wheelset and the track models are both defined using an ‘Arbitrary Lagrangian–Eulerian’ Finite Element approach in combination with modal synthesis. This allows an efficient treatment of the problem, compared to a classical Finite Element approach. The proposed model is suitable to represent train-track interaction effects in a frequency range up to 7 kHz thanks to the detailed description of wheelset and rail deformability. Wheel–rail contact forces and rail vibration under excitation produced by different types of railhead irregularity are investigated in the paper, assessing the effect of different models of wheelset and track flexibility. The results obtained show that the outputs of the model mostly relevant to the investigation of rail corrugation and rolling noise, i.e. wheel–rail contact forces and rail vibration, are highly sensitive to the wheelset and track model adopted

A Time-Domain Model for the Study of High-Frequency Wheelset–Track Interaction

A mathematical model of dynamic wheelset–track interaction is proposed in this paper. The model is defined in the time domain in order to introduce and correctly evaluate non-linear and time-variant phenomena related to the contact model and boundary conditions which play a very important role in rail surface degradation phenomena. The complete model can be divided into three main components: the model of the wheelset,the model of the track and the model of wheel–rail contact forces. In the paper, the wheelset is described as a rotating flexible body, and the gyroscopic and inertial effects associated with wheelset rotation are introduced to this model using an ‘Eulerian’ finite element approach based on 3D quadratic solid elements. The discrete supported track is modelled using finite Timoshenko beam element, which takes into account both the vertical and the lateral rail vibration valid up to 1500 Hz. The wheelset and the track are coupled by means of a contact model based on the nonlinear Hertz and Kalker theories. The flexible components of the interaction model make it possible to describe the train–track dynamics in a relatively high-fre-quency range, which allows the investigation of specific aspects such as rail corrugation. Some numerical results are presented in terms of contact forces and rail–wheel vibration speed in the paper. The effect of wheelset and track flexibility in specific frequency range on train–track interaction dynamics is briefly discussed

Negative Index of Refraction in Optical Metamaterials

An array of pairs of parallel gold nanorods is shown to have a negative refractive index n'=-0.3 at the optical communication wavelength of 1.5 micron. This effect results from the plasmon resonance in the pairs of nanorods for both the electric and magnetic components of light. The refractive index is retrieved from the direct phase and amplitude measurements for transmission and reflection, which are all in excellent agreement with our finite difference time domain simulations. The refraction critically depends on the phase of the transmitted wave, which emphasizes the importance of phase measurements in finding n'.Comment: an improved version (17 pages, 5 figures) with a new sample and additional measurement

A fast technique using output only to localize and quantify multiple damages for multi-degree-of-freedom systems

Vibration-based methods for identifying and evaluating structural damages have been widely studied in the last decades. However, in the state-of-art methods, there are some practical limitations owing to the complicated calculation process and low damage sensitivities. A new method for localizing and quantifying the damages of a beam-like structure based on low-frequency components, including direct current component, of the output signal subject to an arbitrary input excitation, is proposed in this article. The relationship between the low-frequency components of any two adjacent measurement points is investigated, in order to help to understand the link between damages and low-frequency components of outputs. The theoretical derivation of this method begins with a multi-degree-of-freedom structure of the mass-spring-damper chain, and the damage is considered to be a linear combination of local stiffness losses, resulting in changes in structural dynamic behaviors. The validity and feasibility of the proposed damage indicators are proved by numerical and experimental studies. It is further shown that the severity of the damage can be properly identified using the proposed damage indicator. Moreover, a discussion concerning potential detection on multiple nonlinear damages is presented at the end of this article

The role of silicon to increase arsenic tolerance in rice (oryza sativa l.) seedlings by reinforcing anti-oxidative defense

Arsenic is a toxic metalloid which can cause severe problems to plants. On the other hand, silicon is a beneficial element, which supports plants to build resistance under stressed conditions. The objective of the present study was to assess the effect of silicon and arsenic on the various enzymatic, and non-enzymatic antioxidants, in shoots and roots of two rice seedlings (Du-WT and DUOE), for one and two weeks. Seedlings were exposed to four different culture media: a) Control; b) 0.70 mM Si+no As; c) 30 μM As+no Si; d) 30 μM As+0.70 mM Si. Culture media and rice genotypes were arranged in a 8-treatment factorial with three replications. Results showed that response to silicon, arsenic and or combination of them in unstressed rice plants followed similar patterns, and varied depending upon the antioxidant. The addition of As always decreased the values, but together with silicon there was a partial recovery of them. The pattern of plant response was similar regardless the plant tissue or time of exposure to As. Transgenic Dullar rice, under As stress conditions, activated the highest level of antioxidants, especially when seedlings were treated with silicon.Rol del silicio en el incremento de la tolerancia al arsénico en plántulas de arroz mediante el refuerzo de la defensa antioxidativa El arsénico es un metaloide tóxico que puede causar graves problemas a las plantas. Por su parte, el silicio es un elemento beneficioso, que ayuda a desarrollar resistencia en condiciones de estrés. El objetivo del presente estudio fue evaluar el efecto del silicio y el arsénico sobre diversos antioxidantes enzimáticos y no enzimáticos, en brotes y raíces de plántulas de dos genotipos de arroz (Du-WT y DU-OE), durante 1 y 2 semanas. Las plántulas fueron expuestas a cuatro medios de cultivo diferentes: a) Control; b) 0,70 mM Si+no As; c) 30 μM As+no Si; d) 30 μM As+0.70 mM Si. Los medios de cultivo y los genotipos de arroz se organizaron en un factorial de 8 tratamientos con three repeticiones. La respuesta al silicio, el arsénico, y la combinación de ellos en plantas sin estrés siguió patrones similares y varió según el antioxidante. La adición de As siempre disminuyó los valores, pero junto con el silicio produjo una recuperación parcial de los mismos. El patrón de respuesta de la planta fue similar, independientemente del tejido o el tiempo de exposición al As. El arroz Dullar transgénico, bajo condiciones de estrés, activó el nivel más alto de antioxidantes, especialmente cuando las plántulas fueron tratadas con silici

An Actinide Metallacyclopropene Complex: Synthesis, Structure, Reactivity, and Computational Studies

International audienceThe synthesis, structure, and reactivity of an actinide metallacyclopropene were comprehensively studied. The reduction of [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with potassium graphite (KC8) in the presence of diphenylacetylene (PhC≡CPh) yields the first stable actinide metallacyclopropene [η5-1,2,4-(Me3C)3C5H2]2Th(η2-C2Ph2) (2). The magnetic susceptibility data show that 2 is indeed a diamagnetic Th(IV) complex, and density functional theory (DFT) studies suggest that the 5f orbitals contribute to the bonding of the metallacyclopropene Th—(η2-C═C) moiety. Complex 2 shows no reactivity toward alkynes, but it reacts with a variety of heterounsaturated molecules such as aldehyde, ketone, carbodiimide, nitrile, organic azide, and diazoalkane derivatives. DFT studies complement the experimental observations and provide additional insights. Furthermore, a comparison between Th and group 4 metals reveals that Th4+ shows unique reactivity patterns

Glucose Uptake Activities of Bis (2, 3-Dibromo-4, 5-Dihydroxybenzyl) Ether, a Novel Marine Natural Product from Red Alga Odonthaliacorymbifera with Protein Tyrosine Phosphatase 1B Inhibition, In Vitro and In Vivo.

BACKGROUND AND AIMS:Protein tyrosine phosphatase 1B (PTP1B) is a novel therapeutic target for type-2 diabetes, which negatively regulates the insulin signaling transduction. Bis (2, 3-dibromo-4, 5-dihydroxybenzyl) ether (BDDE), a novel bromophenol isolated from the Red Alga, is a novel PTP1B inhibitor. But the anti-diabetic effects are not clear. In the present study, we evaluated the in vitro and in vivo antidiabetic effects of BDDE. METHODS:The insulin-resistant HepG2 cells were used to evaluate the in vitro antidiabetic effects of BDDE. MTT assay was used to determine the safety concentrations in HepG2 cells. Glucose assay kit was used to check glucose uptake after treated with BDDE. Western blotting assay was used to explore the potent mechanisms. The db/db mice were used to evaluate the in vivo antidiabetic effects of BDDE. Body weight, blood glucose, Glycated hemoglobin (HbA1c), lipid profile, and insulin level were checked at the respective time points. Gastrocnemii were dissected and used to analyze the PTP1B and insulin receptor β (IRβ) expression. RESULTS:BDDE increased the insulin-resisted glucose uptake in HepG2 cells. BDDE also decreased the expression of PTP1B and activated the substrates and downstream signals in insulin signal pathway, such as IRβ, insulin receptor substrate-1/2 (IRS1/2), phosphoinositide 3-kinase (PI3K), and protein kinase B (PKB/Akt). In the db/db mice model, BDDE significantly decreased the blood glucose, HbA1c and triglyceride (TG) levels. BDDE also decreased the expression of PTP1B and activated the phosphorylation of IRβ in gastrocnemii. Moreover, BDDE at high doses downregulated the body weight without affecting food and water intake. CONCLUSION:Our results suggest that BDDE as a new PTP1B inhibitor improves glucose metabolism by stimulating the insulin signaling and could be used in the treatment of type-2 diabetes mellitus

Thorium Oxo and Sulfido Metallocenes: Synthesis, Structure, Reactivity, and Computational Studies

The synthesis, structure, and reactivity of thorium oxo and sulfido metallocenes have been comprehensively studied. Heating of an equimolar mixture of the dimethyl metallocene [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂ThMe₂ (<b>2</b>) and the bis-amide metallocene [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂Th(NH-<i>p</i>-tolyl)₂ (<b>3</b>) in refluxing toluene results in the base-free imido thorium metallocene, [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂ThN(<i>p</i>-tolyl) (<b>4</b>), which is a useful precursor for the preparation of oxo and sulfido thorium metallocenes [η⁵-1,2,4-(Me₃C)₃C₅H₂]₂ThE (E = O (<b>5</b>) and S (<b>15</b>)) by cycloaddition–elimination reaction with Ph₂CE (E = O, S) or CS₂. The oxo metallocene <b>5</b> acts as a nucleophile toward alkylsilyl halides, while sulfido metallocene <b>15</b> does not. The oxo metallocene <b>5</b> and sulfido metallocene <b>15</b> undergo a [2 + 2] cycloaddition reaction with Ph₂CO, CS₂, or Ph₂CS, but they show no reactivity with alkynes. Density functional theory (DFT) studies provide insights into the subtle interplay between steric and electronic effects and rationalize the experimentally observed reactivity patterns. A comparison between Th, U, and group 4 elements shows that Th⁴⁺ behaves more like an actinide than a transition metal