Effects of NaCl on growth and activity of enzymes involved in carbon metabolism in leaves of tobacco (Nicotiana rustica)

The adverse effects of salt should not be the same in tobacco plants exposed to a permanent and transient high concentration of NaCl in its environment. Experiments were conducted in order to verify the hypothesis of reversibility of NaCl effects. The study of this reversibility is checked by monitoring a number of parameters in pre-stressed plants and then, replaced in normal conditions. Plants previously grown for 30 days on basic medium were treated for 7 days with 200 mM NaCl and then placed back on the basic culture without NaCl for 10 days. The results show that NaCl suppression leads to a resumption of growth with a decrease in the concentration of sodium (Na+) and chloride ions (Cl-). Hence, potassium content (K+) increases gradually in the leaves to reach the level obtained with unstressed plants. At the same time, there is a stimulation of the activities of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase isoenzymes (NAD, NADP, NADH and NADPH-MDH) and isocitrate dehydrogenase (ICDH) after NaCl had been removed. Along with the boosting of the activity of these enzymes involved in the process of carbon assimilation, there is a gradual decrease in soluble sugars content, suggesting a resumption of the normal activity of photosynthetic assimilation process. All these results verify our hypothesis and can be explained by the ability of the plant to dilute the effects of Na+ and Cl- during the recovering period. An important result of this study is that a transient salinity is not necessarily followed by a significant depreciation in product yield or quality.Keywords: Tobacco, NaCl, reversibility, phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), isocitrate dehydrogenase (ICDH

Experimental study and multi-physics modelling of concrete under supercritical carbonation

This paper presents both experimental study and multi-physics modelling of supercritical carbonation of concrete. A novel mathematical model is proposed to simulate random distribution of coarse aggregates in concrete. Supercritical carbonation tests of concrete are carried out and the measured carbonation depth is compared with the simulation results. On the basis of previous research on random field of porosity and supercritical carbonation of cement mortar, a new supercritical carbonation model is developed to study the effect of randomly distributed coarse aggregates and porosity on the irregularities of carbonation depth of concrete. The effect of the type, volume fraction and gradation of coarse aggregates and the porosity of ITZ on the distribution of irregular carbonation depth are also studied. The results demonstrate that the proposed two-dimensional random coarse aggregates model can be used satisfactorily to generate different types, volume fraction and gradation of coarse aggregates with the designed mix proportion within a confined space. The method provides a better and more realistic predictive model for simulating carbonation depth of concrete due to random distribution of coarse aggregates and porosity

Spontaneous Diabetes in Hemizygous Human Amylin Transgenic Mice That Developed Neither Islet Amyloid nor Peripheral Insulin Resistance

OBJECTIVES—We sought to 1) Determine whether soluble-misfolded amylin or insoluble-fibrillar amylin may cause or result from diabetes in human amylin transgenic mice and 2) determine the role, if any, that insulin resistance might play in these processes

An effective microscale approach for determining the anisotropy of polymer composites reinforced with randomly distributed short fibers

In this paper, an effective microscopic modeling scheme is presented to analyze mechanical properties of composites with random short fibers. To this end, the displacement-load tests of the standard samples, which are acquired by cutting a short fiber-reinforced composite plate of 650 mm × 650 mm × 2.5 mm, are firstly executed under the quasi-static tensile loads. To identify the geometric sizes of the short fibers and their distributions at microscopic scale, the advanced micro-computed tomography (micro-CT) is employed by testing a small sample of 1 cm × 2.5 mm × 2.5 mm. On this basis, a simplified microscopic model is reconstructed by the 3D parametric finite-volume direct averaging micromechanics (FVDAM) theory according to the statistic results of the micro-CT images. The proposed method is further validated by comparing the effective modulus obtained from tensile tests. The scanning electron microscopy (SEM) is also used to visualize the fracture morphology of the fibers. It is found that brittle fracture occurs in the short-fibers paralleled to the external loading

Real-Time Resolution of the Forward Kinematic Model for a New Spherical Parallel Manipulator

International audienceThis paper discusses the comparison between three methods used to solve the Forward Kinematic Model (FKM) of a New Spherical Parallel Manipulator (New SPM). The three methods are: a classical method (Classical FKM) using three sensors installed in the base, an improved method (Improved FKM) using an extra sensor installed on the moving platform and a serial method (Serial FKM) using three sensors installed on one leg of the parallel manipulator. Both the accuracy and the calculation time are compared. The serial approach was chosen, thanks to its simplicity and the fast calculation time, despite the small error compared to the other methods

Microscopic failure characteristics and critical length of short glass fiber reinforced composites

Short glass fiber reinforced composites (SGFRC) are frequently used to manufacture parts with complex surfaces by injection or compression molding. It was found that the length of fibers is often reduced during the manufacturing processes. To understand the causes of the change in fiber length, ex-situ 3D CT images are taken from tensile experiments to extract the information of the microstructure of the SGFRC, including fiber length, orientation and breakage. In the calculation of the critical length, the Kelly model is modified to include the effect of the stresses at fiber ends and the mechanical effect of internal pore defects on the composites. It is found that the microscopic interaction of short fibers breaks longer fibers, until they are shorter than the critical length. Through comparisons, it is found that the modified Kelly model is more accurate in predicting critical length of short fibers. In this study, micro-failure modes, such as fiber pulling out, interface debonding, matrix damage and pore destruction, are all characterized by micro-CT and scanning electronic microscope to analyze the complex failure mechanisms. The micro failure modes are mainly attributed to the micro geometric features and mass fraction of short fibers

Inherently multifunctional geopolymeric cementitious composite as electrical energy storage and self-sensing structural material

© 2018 Elsevier Ltd In this paper, we demonstrate for the first time that potassium-geopolymeric (KGP) cementitious composites can be tuned to store and deliver energy, and sense themselves without adding any functional additives or physical sensors, thus creating intelligent concrete structures with built-in capacitors for electrical storage and sensors for structural health monitoring. Density function theory (DFT)-based simulations were performed to determine the electronic properties of the KGP cementitious composite and understand its conduction mechanism. Experimental characterization was also conducted to determine the structure, chemical composition, conduction mechanism, energy storage and sensing capabilities of the KGP cementitious composite. The DFT simulations suggested that the KGP cementitious composite relies on the diffusion of potassium (K+) ions to store electrical energy and sense mechanical stresses. The geopolymeric cementitious composite exhibited a good room temperature ionic conductivity in the range of 12 (10−2 S/m) and an activation energy as high as 0.97 eV. The maximum power density of the KGP capacitors is about 0.33 kW/m2 with a discharge life of about 2 h. The KGP stress sensors showed high sensitivity to compressive stress: 11 Ω/MPa based on impedance measurement and 0.55 deg/MPa based on phase measurement. With further development and characterization, the KGP cementitious composite can be an integral part of concrete structures in the form of a battery to store and deliver power, and sensors to monitor the structural integrity of urban infrastructure such as bridges, buildings and roads

Experimental study on thermal performance of ultra-high performance concrete with coarse aggregates at high temperature

Ultra-high performance concrete (UHPC) exhibits superior mechanical and durability performance with very high compressive strength. Compared with ordinary concrete, it is more environmentally friendly and has the great potential to be a practical solution to improve the sustainability of infrastructure. This study focuses on examining thermal properties of UHPC with coarse aggregates (CA-UHPC) subjected to temperature ranged from 20 °C ∼ 900 °C, including changes in macro and micro morphology before and after high temperatures, thermal conductivity, mass loss, specific heat and thermal expansion. The effects of high temperature, coarse aggregate and steel fiber content on the thermal performance of the material will be evaluated both qualitatively and quantitatively. Experimental results show that high temperature greatly affects thermal properties of CA-UHPC. Coarse aggregates also have a considerable influence on the thermal properties. Steel fibers, however, have little effect on the thermal properties. Based on the test results, meso calculation formulas are proposed to predict the thermal properties, which can be used in the design of structural components made of CA-UHPC

Evolution of ITZ and its effect on the carbonation depth of concrete under supercritical CO2 condition

In this paper, supercritical carbonation tests of concrete specimens with different water-to-cement ratios are carried out. In the test, the thickness of interfacial transition zone (ITZ) of the concrete is determined by the distribution of Ca/Si ratio across the interface between the coarse aggregate and cement paste. The microhardness distribution, microstructure and porosity of the ITZ before and after supercritical carbonation are analyzed. A geometrical and physical model considering the distribution of porosity, coarse aggregates, ITZ, and the supercritical carbonation of concrete is proposed, by which cracks, pores, calcium carbonates, and C-S-H gel at the interface of coarse aggregates and cement paste can be studied. The overall microstructures are relatively compacted after supercritical carbonation. The thickness of ITZ of concrete is reduced from 47-79 μm to 35–51 μm after supercritical carbonation. The average value and variance of carbonation depth of concrete increase with the increase of the thickness and porosity of ITZ. Comparing the carbonation results of concrete with different thicknesses and porosity of ITZ, it appears that porosity of ITZ has greater impact on the carbonation depth of concrete