No abstract

The O/O ratio at both molecular and positional levels in the carbohydrates of higher plants is a reliable proxy for the plant growth environment, and a potential indicator of the plant photosynthetic carbon assimilation mode, and its physiological, biochemical and metabolic status. The lack of exploitable nuclear resonance in O andO and the extremely low O abundance make the NMR-based PSIA (position-specific isotopic analysis) a significant challenge. In this Article, an alternative three-step wet chemistry based method for accessing theO/O of glucose O-3 is presented. The O atoms (OH groups) at positions 1, 2, 5, and 6 were first protected by acetonation (converting glucose to 1,2;5,6-di- O-isopropylidene-glucofuranose). The protected glucose was then esterified at O-3 by thionoformylation. Subsequent Barton-McCombie deoxygenation quantitatively removed the O-3 from the protected sugar. Mass balance was then applied to calculate the O/O of O-3 using the isotopic values of the protected sugar before and after the deoxygenation step. The method is innovative in that (i) isolation and purification of individual compounds for O by EA/Pyrolysis/IRMS analysis is unnecessary as the reaction mixture can be analyzed on a GC/Pyrolysis/IRMS; (ii) sample quantity is dramatically reduced; and (iii) the approach to access the O-3 isotopic signal can be easily expanded to other positions within glucose and other sugars. It was shown that O-3 is enriched by 12 mUr relative to the molecular average (O-2-O-6) for a glucose of C photosynthetic origin. We highlighted the potential applications of the intramolecular O isotopic heterogeneity of glucose this method revealed.

Based on silicon on insulator (SOI) technology, a novel high temperature pressure sensor with high frequency response is designed and fabricated, in which a buried silicon dioxide layer in the silicon material is developed by the separation by implantation of oxygen (SIMOX) technology. This layer can isolate leak currents between the top silicon layer for the detecting circuit and body silicon at a temperature of about 200 °C. In addition, the technology of silicon and glass bonding is used to create a package of the sensor without internal strain. A structural model and test data from the sensor are presented. The experimental results showed that this kind of sensor possesses good static performance in a high temperature environment and high frequency dynamic characteristics, which may satisfy the pressure measurement demands of the oil industry, aviation and space, and so on.

Summary We present a vibration metre for conductor vibration measurement that is highly accurate due to its robustness against interference from the electromagnetic environment. According to the range of load currents in the transmission line, a power supply module based on induction charging is designed for the vibration metre. The module is composed of three parts: the mutual inductor obtains electrical energy from the transmission line based on the electromagnetic induction principle, the power controller manages the charging and discharging of a lithium battery, and the lithium battery supplies power to all modules and sensors. A cantilever beam displacement sensor is used to measure the vibration amplitude of the conductor. Moreover, a calibration method based on two‐dimensional regression is proposed to address the linear variation of the sensor output due to frequency variations. The corresponding test platform for power supply and accuracy is established, and the experiments verify the feasibility and accuracy of the vibration metre. Furthermore, the vibration metre is tested on a conductor spanning 105 m at Xi'an Polytechnic University. The test data show the number of amplitudes appearing at different frequencies within 10 days, which indicates the characteristics of vibration during this time.

In order to obtain the optimal technological parameters of lettuce vacuum osmotic dehydration, the effects of osmotic temperature, slice thickness, sucrose concentration, and vacuum degree on the vacuum osmotic dehydration were explored. The lettuce water loss rate and solid gain rate decreased with the increase of slice thickness and vacuum degree, and increased with the increase of sucrose concentration and osmotic temperature. Response surface methodology was applied to analyze the infl uence of the four infl uential factors on the evaluated parameters and the optimization of lettuce vacuum osmotic dehydration was studied. The results indicated that, within the experimental scope, the optimized technological parameters of lettuce vacuum osmotic dehydration are the temperature of 28 o C, the slice thickness of 2 mm, sucrose concentration of 47%, the vacuum degree of 22 kPa, and the water loss rate and solid gain rate are 72.16% and 11.82%, respectively.