13C Isotope Labelling to Follow the Flux of Photorespiratory Intermediates

Measuring the carbon flux through metabolic pathways in intact illuminated leaves remains challenging because of, e.g., isotopic dilution by endogenous metabolites, the impossibility to reach isotopic steady state, and the occurrence of multiple pools. In the case of photorespiratory intermediates, our knowledge of the partitioning between photorespiratory recycling, storage, and utilization by other pathways is thus rather limited. There has been some controversy as to whether photorespiratory glycine and serine may not be recycled, thus changing the apparent stoichiometric coefficient between photorespiratory O2 fixation and CO2 release. We describe here an isotopic method to trace the fates of glycine, serine and glycerate, taking advantage of positional 13C content with NMR and isotopic analyses by LC–MS. This technique is well-adapted to show that the proportion of glycerate, serine and glycine molecules escaping photorespiratory recycling is very small.

Электронно-пучковая кристаллизация тонких пленок аморфного субоксида кремния

Polycrystalline silicon (poly-Si) has been obtained for the first time as a result of an electron beam irradiation of amorphous hydrogenated silicon suboxide films with a stoichiometric coefficient of 0.5 (a-SiO0.5:H) and a thickness of 580 nm. The accelerating voltage of the electron beam was 2000 V, and the beam current was 100 mA. Raman spectra of silicon films after annealing are obtained depending on the time of electron beam irradiation of the initial material. It is shown that as a result of annealing, poly-Si is formed, the stress in which varied from compression to tension depending on the time of exposure.

Индий-индуцированная кристаллизация тонких пленок аморфного субоксида кремния

A novel fabrication method of polycrystalline silicon by indium-induced crystallization (InIC) of amorphous silicon suboxide thin films with a stoichiometric coefficient of 0.5 (a-SiO0.5) is proposed. It was shown that the use of indium in the annealing process of a SiO0.5 allowed to decrease the crystallization temperature to 600°С which was significantly lower than the solid-phase crystallization temperature of the material - 850°С. As a result of the high-vacuum InIC of a-SiO0.5, the formation of free-standing micron-sized crystalline silicon particles took place.

Calcination Influence on the Structure and Morphology of Zirconia Synthesized by Combustion Reaction

This research aims to synthesize ZrO2by combustion reaction in batches of 15 g of the product and to evaluate the calcination influence on the structural and morphological characteristic about synthesized sample. For the synthesis of ZrO2, the stoichiometry of phase was established in accordance with the propellants and explosives chemical concept, whereas the stoichiometric coefficient φ =1. After the synthesis, the sample as synthesized was calcined at 600 and 700°C and subsequently characterized by XRD, SEM, textural analysis (BET) and FTIR. The results have shown to the sample as synthesized and then calcined at 600°C the majority phase formation of orthorhombic zirconia with monoclinic phase dashes. The temperature increase to 700°C, has been transformed a part of the orthorhombic ZrO2to a monoclinic phase, contributing to a surface area reduction of the samples, showing irregular agglomerates in morphology, with adsorption/desorption isotherms type IV and mesoporosity characteristic.

Method to obtain carbon nano-onions by pyrolisys of propane

We present a new and simple method for carbon nano-onions (CNOs) production which is based on the pyrolysis of Propane. CNOs are originated in a laminar premixed Propane/Oxygen flame of approximately 1.8 of stoichiometric coefficient. The stream of gasses resulting from the combustion drives the carbon particles towards the aluminium surface on which nano-onions are deposited and collected. The structure and size of the deposited carbon onion on the metal wall are characterized by High Resolution Transmission Electron Microscopy technique (HRTEM). The experimental images show the presence of two different types of CNOs. The first particles have diameters in the range of 18-25 nm and the second ones around 10 nm.

Derivation of the stoichiometric coefficient of water (ν_w) to account for water uptake by atmospheric aerosols

In this work we derive the effective stoichiometric coefficient of water (vw), introduced by Metzger and Lelieveld, 2007 (ML07), from first principles. We give examples of the application of vw in CPU efficient computations of the Deliquescence Relative Humidity (DRH) and the water uptake of atmospheric aerosols, being important parameters in atmospheric chemistry and climate modeling. We show that the application of vw in a gas/liquid/solid aerosol equilibrium partitioning model (EQSAM3) leads to results that are in excellent agreement with those of widely used thermodynamic (reference) models (E-AIM and ISORROPIA2) for various single salt solutions (NaCl, NH4NO3, (NH4)2SO4, NH4HSO4, NaHSO4) and the corresponding mixed solutions (including (NH4)3H(SO4)2 and Na3H(SO4)2), notwithstanding the distinct different theoretical and numerical concepts on which these models are based.

Buffer capacity in multiple chemical reaction systems involving solid phases

The buffer capacity of a chemical species in a multiple chemical reaction system is discussed in terms of a special class of stoichiometrically unique reactions referred to as response reactions (RERs). More specifically, it is shown that the buffer capacity may be partitioned into a sum of contributions associated with RERs. This finding provides a deeper understanding of the factors that determine the buffer capacity. In particular, the main contributions to the buffer capacity come from the RERs involving the most abundant species. Concomitantly, the RERs approach provides a simple stoichiometric algorithm for the derivation and analysis of the buffer capacity that may be easily implemented into a computer software.Key words: buffer capacity, response reaction, heterogeneous system, stoichiometric coefficient.

Can we assess the model complexity for a bioprocess: theory and example of the anaerobic digestion process

In this paper we propose a methodology to determine the structure of the pseudo-stoichiometric coefficient matrix K in a mass balance based model, i.e. the maximal number of biomasses that must be taken into account to reproduce an available data set. It consists in estimating the number of reactions that must be taken into account to represent the main mass transfer within the bioreactor. This provides the dimension of K. The method is applied to data from an anaerobic digestion process and shows that even a model including a single biomass is sufficient. Then we apply the same method to the “synthetic data” issued from the complex ADM1 model, showing that the main model features can be obtained with two biomasses.

Chemical sulfide oxidation of wastewater - effects of pH and temperature

In this study, the kinetics and stoichiometry of chemical sulfide oxidation of wastewater from sewer networks were investigated. Based on experiments, it was shown that the stoichiometry could be considered identical for wastewater from two sampling sites. However, the kinetics differed significantly among the wastewaters from the two sites. Effects of pH and temperature were investigated in the pH and temperature ranges 5-9 and 5-25°C, respectively. The rate of chemical sulfide oxidation could be related to the dissociation of H2S to HS-, with HS- being oxidized at a higher rate than H2S. The temperature dependency of the chemical sulfide oxidation rate was described using an Arrhenius relationship. The oxidation rate was found to double with a temperature increase of 12¡C. The stoichiometry of the chemical oxidation was not significantly affected by varying pH and temperature. Based on the experiments, a general rate equation, including a stoichiometric coefficient describing chemical sulfide oxidation in wastewater was proposed, enabling the process to be incorporated into sewer process models that can predict odor and corrosion problems.